Alkanes and Their Nomenclature Quiz
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Questions and Answers

Which type of strain is primarily associated with the rotation around single bonds in alkanes?

  • Angle strain
  • Steric strain
  • Torsional strain (correct)
  • Ring strain

What is the correct IUPAC name for a three-carbon alkane?

  • Propionic acid
  • Propanedione
  • Propanol
  • Propane (correct)

Which conformation type is most stable for butane due to staggered interactions?

  • Gauche conformation
  • Eclipsed conformation
  • Anti conformation (correct)
  • Planar conformation

How are primary, secondary, and tertiary carbons classified in alkanes?

<p>Based on the number of other carbon atoms they are connected to (D)</p> Signup and view all the answers

Which of the following statements about alkanes is incorrect?

<p>Alkanes do not float on water due to high density. (B)</p> Signup and view all the answers

What is the correct suffix for naming alkanes?

<p>-ane (B)</p> Signup and view all the answers

In naming a branched alkane, how should you identify the parent chain?

<p>It is the longest chain of carbon atoms. (A)</p> Signup and view all the answers

When there are two identical substituents on a carbon chain, how should you number them?

<p>From the end that gives the lower number to the first substituent encountered. (D)</p> Signup and view all the answers

Which prefix indicates the presence of three identical substituents?

<p>tri- (C)</p> Signup and view all the answers

What classification describes a carbon atom bonded to three other carbon atoms?

<p>Tertiary (3°) (C)</p> Signup and view all the answers

Which structure corresponds to the general formula for cycloalkanes?

<p>CnH2n (A)</p> Signup and view all the answers

In which order should substituents be listed when naming a compound with multiple different substituents?

<p>In alphabetical order regardless of position. (D)</p> Signup and view all the answers

Which term is included in alphabetization when naming alkane substituents?

<p>iso- (A)</p> Signup and view all the answers

What is the general formula for alkanes?

<p>C_nH_{2n+2} (A)</p> Signup and view all the answers

Which of the following describes constitutional isomers?

<p>Compounds with the same molecular formula but different connectivity. (B)</p> Signup and view all the answers

Which prefix in IUPAC nomenclature denotes a 6-carbon alkane?

<p>hex- (C)</p> Signup and view all the answers

In the context of alkanes, what type of strain is associated with the eclipsing conformations?

<p>Torsional strain (D)</p> Signup and view all the answers

What type of carbon is classified as having four distinct substituents?

<p>Quaternary carbon (C)</p> Signup and view all the answers

Which of the following is a correct feature of the line-angle formula in representing alkanes?

<p>Each line represents a single bond. (B)</p> Signup and view all the answers

For an alkane with a 10-carbon chain, what would be its hydrogen count according to the general formula?

<p>22 (D)</p> Signup and view all the answers

Which term describes a group derived from an alkane by removing one hydrogen atom?

<p>Alkyl group (D)</p> Signup and view all the answers

An alkane is a saturated hydrocarbon with only carbon-carbon double bonds.

<p>False (B)</p> Signup and view all the answers

The general formula for alkanes is CnH2n.

<p>False (B)</p> Signup and view all the answers

All carbon atoms in alkanes are sp2 hybridized.

<p>False (B)</p> Signup and view all the answers

Constitutional isomers have the same molecular formula but different structural connectivity.

<p>True (A)</p> Signup and view all the answers

The prefix used in IUPAC nomenclature indicates the number of carbon atoms in a molecule.

<p>True (A)</p> Signup and view all the answers

In the line-angle formula, each line represents a double bond.

<p>False (B)</p> Signup and view all the answers

Aliphatic hydrocarbons are another name for cyclic hydrocarbons.

<p>False (B)</p> Signup and view all the answers

The bond angles in alkanes are approximately 109.5°.

<p>True (A)</p> Signup and view all the answers

Planar cyclopentane exhibits 12 fully eclipsed C-H bonds, resulting in a torsional strain of approximately 52 kJ/mol.

<p>False (B)</p> Signup and view all the answers

The chair conformation of cyclohexane is more stable than the boat conformation by 27 kJ/mol.

<p>True (A)</p> Signup and view all the answers

In a chair conformation, both equatorial and axial C-H bonds are aligned parallel to the imaginary axis of the ring.

<p>False (B)</p> Signup and view all the answers

The angle strain in cyclopentane's envelope conformation is approximately 110°.

<p>False (B)</p> Signup and view all the answers

There are two equivalent chair conformations in cyclohexane that interconvert via a twist conformation.

<p>False (B)</p> Signup and view all the answers

Methylcyclohexane has only one stable chair conformation due to the presence of steric strain.

<p>False (B)</p> Signup and view all the answers

Staggered interactions in cyclohexane are eliminated in the boat conformation.

<p>False (B)</p> Signup and view all the answers

All C-H bonds that are axial in one chair conformation become equatorial in the alternative chair conformation of cyclohexane.

<p>True (A)</p> Signup and view all the answers

The name of an alkane consists only of a prefix and the suffix -ene.

<p>False (B)</p> Signup and view all the answers

The longest chain of carbon atoms in a branched alkane is referred to as the parent chain.

<p>True (A)</p> Signup and view all the answers

In naming substituents, prefixes such as di-, tri-, and tetra- are included in the alphabetical order.

<p>False (B)</p> Signup and view all the answers

If a cycloalkane has only one substituent, it is necessary to give it a numbering system.

<p>False (B)</p> Signup and view all the answers

A carbon bonded to three other carbons is classified as primary.

<p>False (B)</p> Signup and view all the answers

The general formula for cycloalkanes is CnH2n.

<p>True (A)</p> Signup and view all the answers

The number of identical substituents in alkanes can be indicated using the prefixes mono-, di-, and tri-.

<p>False (B)</p> Signup and view all the answers

To number a ring in a cycloalkane with three or more substituents, it should be done to give the lowest set of numbers.

<p>True (A)</p> Signup and view all the answers

The average density of liquid alkanes is about 1.5 g/mL.

<p>False (B)</p> Signup and view all the answers

Oxidation is essential for using alkanes as energy sources.

<p>True (A)</p> Signup and view all the answers

Natural gas primarily consists of propane.

<p>False (B)</p> Signup and view all the answers

Synthesis gas is a mixture of carbon dioxide and hydrogen.

<p>False (B)</p> Signup and view all the answers

Methanol can be produced from synthesis gas.

<p>True (A)</p> Signup and view all the answers

Cis-trans isomers can be interconverted by rotation about sigma bonds.

<p>False (B)</p> Signup and view all the answers

Cyclopentane is often viewed through an edge or from above.

<p>True (A)</p> Signup and view all the answers

For trans-1,4-dimethylcyclohexane, the diaxial chair conformation is more stable than the diequatorial chair conformation.

<p>False (B)</p> Signup and view all the answers

High-molecular-weight alkanes (18 or more carbons) are typically liquids at room temperature.

<p>False (B)</p> Signup and view all the answers

Cis-1,4-dimethylcyclohexane has alternative chairs that are of equal stability.

<p>True (A)</p> Signup and view all the answers

Dispersion forces are weak intermolecular forces present in polar compounds.

<p>False (B)</p> Signup and view all the answers

Low-molecular-weight alkanes are gases at room temperature.

<p>True (A)</p> Signup and view all the answers

Cyclohexane is commonly represented as a planar hexagon when viewed from the side.

<p>True (A)</p> Signup and view all the answers

The Eclipsed conformation of a carbon-carbon single bond is characterized by the atoms on one carbon being as far apart as possible from the atoms on an adjacent carbon.

<p>False (B)</p> Signup and view all the answers

Torsional strain is the strain that occurs when nonbonded atoms separated by three bonds are forced into a staggered arrangement.

<p>False (B)</p> Signup and view all the answers

Cyclopentane exhibits significant angle strain due to its bond angles deviating from the tetrahedral angle.

<p>False (B)</p> Signup and view all the answers

The lowest energy conformation for an alkane is the eclipsed conformation.

<p>False (B)</p> Signup and view all the answers

The IUPAC naming system includes a prefix indicating the number of carbon atoms in the parent compound.

<p>True (A)</p> Signup and view all the answers

The term 'butanol' corresponds to butan-1-ol, indicating that it is an alcohol compound.

<p>True (A)</p> Signup and view all the answers

Staggered conformation achieves the highest energy state due to maximum interaction between nonbonded atoms.

<p>False (B)</p> Signup and view all the answers

The IUPAC name 'ethyne' indicates that the compound contains a triple bond between carbon atoms.

<p>True (A)</p> Signup and view all the answers

Which statement is true regarding the stability of cis and trans alkenes?

<p>Trans alkenes have less nonbonded interaction strain than cis alkenes. (B)</p> Signup and view all the answers

What kind of bond is formed by the overlap of sp hybrid orbitals in an alkyne?

<p>A sigma bond (A)</p> Signup and view all the answers

What determines the acidity of terminal alkynes compared to alkanes and alkenes?

<p>The stability of the anion derived from each class of hydrocarbon (C)</p> Signup and view all the answers

What geometric arrangement is associated with the carbon atoms in a double bond of an alkene?

<p>Trigonal planar arrangement with 120° bond angles (D)</p> Signup and view all the answers

Which hybrid orbital has the highest s character in a terminal alkyne anion?

<p>sp hybrid orbital (B)</p> Signup and view all the answers

What type of hydrocarbon contains one or more carbon-carbon double bonds?

<p>Alkene (B)</p> Signup and view all the answers

How does the s character of an orbital affect the stability of the anion?

<p>Greater s character results in a more stable anion (C)</p> Signup and view all the answers

Why is the double bond in alkenes subject to restricted rotation?

<p>The presence of pi bonds prevents rotation. (D)</p> Signup and view all the answers

Which compound is considered the most acidic among alkanes, alkenes, and alkynes?

<p>Terminal alkyne (A)</p> Signup and view all the answers

What is an example of an unsaturated hydrocarbon?

<p>Ethylene (C)</p> Signup and view all the answers

What characterizes the configuration of carbon-carbon double bonds in compounds such as pyrethrin II?

<p>They exhibit both cis and trans isomerism (D)</p> Signup and view all the answers

In an alkyne, how many pi bonds are present in its triple bond?

<p>Two (B)</p> Signup and view all the answers

What is a key feature of cyclopropene through cycloheptene in terms of double bond configuration?

<p>They must have a cis configuration. (B)</p> Signup and view all the answers

For a compound like 2,4-heptadiene, how many cis-trans isomers are possible?

<p>Four (C)</p> Signup and view all the answers

Which statement correctly describes the solubility of alkenes and alkynes?

<p>They are insoluble in water and soluble in nonpolar organic solvents. (B)</p> Signup and view all the answers

What occurs when a strong base reacts with a terminal alkyne?

<p>An alkyne anion is produced. (D)</p> Signup and view all the answers

Why can hydroxide ion not act as a strong base in reaction with a terminal alkyne?

<p>Water is a stronger acid than a terminal alkyne. (D)</p> Signup and view all the answers

How does the acidity of terminal alkynes compare to that of alkenes and alkanes?

<p>Terminal alkynes are more acidic than both alkenes and alkanes. (A)</p> Signup and view all the answers

What type of attractive forces exist between the molecules of alkenes and alkynes?

<p>Dispersion forces (D)</p> Signup and view all the answers

How many C-C double bonds in vitamin A can exhibit cis-trans isomerism?

<p>Four (B)</p> Signup and view all the answers

What infix is used in IUPAC nomenclature to indicate the presence of a carbon-carbon double bond?

<p>-ene- (A)</p> Signup and view all the answers

How do you determine the priority of substituents when assigning E,Z configuration?

<p>According to atomic number, with higher atomic numbers given higher priority (D)</p> Signup and view all the answers

When numbering a parent chain to name an alkyne, what is the main goal?

<p>To give the first carbon of the triple bond the lower number (B)</p> Signup and view all the answers

Which statement correctly describes the E,Z configuration of alkenes?

<p>Z indicates that groups of higher priority are on the same side of the double bond (B)</p> Signup and view all the answers

What is a unique characteristic of cycloalkenes regarding their numbering?

<p>Numbering starts with the two carbons of the double bond (B)</p> Signup and view all the answers

What do low-molecular-weight alkenes typically prefer in terms of nomenclature?

<p>They commonly use trivial or common names (C)</p> Signup and view all the answers

When two substituents are of equal priority in an E,Z configuration, which method should be applied to determine priority?

<p>Look to the next set of atoms until the first point of difference (D)</p> Signup and view all the answers

In IUPAC nomenclature for alkenes, which of the following is correct regarding substituents?

<p>Follow IUPAC rules for proper numbering and naming (A)</p> Signup and view all the answers

Flashcards

Alkane Naming (Unbranched)

Prefix + -ane suffix for unbranched alkane chains

Alkane Parent Chain

Longest continuous carbon chain in branched alkanes

Substituent Numbering (Single)

Number the chain from the end giving the substituent the lowest number

Multiple Identical Substituents

Number chain from end giving lowest first substituent number; use di-, tri-, etc.

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Multiple Different Substituents

Alphabetize substituent names, then number from the end giving the substituent encountered first the lower number.

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Alphabetization of Substituents

Prefixes like di-, tri- are excluded from alphabetization; but 'iso' is included.

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Classification Primary, Secondary, Tertiary, Quaternary Carbons

Classifies carbons based on the number of other carbon atoms they are bonded to (1°, 2°, 3°, 4°)

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Cycloalkane General Formula

CnH2n

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Alkane Density

Alkane liquids and solids are typically less dense than water, floating on its surface.

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Constitutional Isomers

Different compounds with the same molecular formula but different structural arrangements.

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Heat of Combustion

The heat released when one mole of a substance is completely burned (oxidized) to carbon dioxide and water.

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Natural Gas Composition

Primarily composed of methane (90-95%) and smaller amounts of ethane (5-10%).

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Synthesis Gas

A mixture of carbon monoxide and hydrogen used for producing other chemicals.

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Hydrocarbon

A compound made only of carbon and hydrogen atoms.

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Saturated Hydrocarbon

A hydrocarbon containing only single bonds between carbon atoms.

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Alkane

A saturated hydrocarbon with carbon atoms arranged in a chain.

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Constitutional Isomers

Compounds with the same molecular formula but different atom arrangements.

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Alkane General Formula

CnH2n+2, where 'n' is the number of carbon atoms.

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Alkyl Group

A substituent derived from an alkane by removing a hydrogen atom.

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IUPAC Nomenclature

A systematic way to name organic compounds, including alkanes.

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Tetrahedral Geometry

The shape of a molecule where the central atom is surrounded by four other atoms with bond angles of approximately 109.5°.

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Hydrocarbon

A compound made only of carbon and hydrogen.

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Saturated Hydrocarbon

Hydrocarbon with only single bonds between carbons.

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Alkane

A saturated hydrocarbon with a chain of carbons.

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Constitutional Isomers

Different compounds with same molecular formula but different atom arrangement.

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Alkane General Formula

CnH2n+2, where 'n' is the number of carbon atoms.

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Alkyl Group

A substituent derived from an alkane by removing a hydrogen atom.

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IUPAC Nomenclature

A systematic way to name organic compounds, including alkanes.

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Tetrahedral Geometry

A molecule shape where central atom is surrounded by four atoms with bond angles of ~109.5°.

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Alkane Naming (Unbranched)

Unbranched alkanes are named using a prefix followed by the suffix -ane.

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Parent Chain (Branched)

The longest continuous chain of carbon atoms in a branched alkane.

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Substituent Numbering (Single)

Number the parent chain from the end that gives the substituent the lowest possible number.

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Multiple Identical Substituents

Use prefixes (di, tri, tetra, etc.) to show how many times a substituent appears, then lowest number.

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Multiple Different Substituents

Alphabetize substituent names first, then the lowest numbering.

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Alphabetization (Substituents)

Prefixes (di, tri, etc.) are ignored in alphabetical sorting, but 'iso' is included.

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Classification of Carbons

Primary (1°), Secondary (2°), Tertiary (3°), and Quaternary (4°) carbons are classified according to the number of carbons they are attached to.

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Cycloalkane General Formula

The formula for cycloalkanes is CnH2n.

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IUPAC Nomenclature

A systematic method for naming organic compounds.

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Conformation

Different 3D arrangements of atoms due to bond rotation.

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Staggered conformation

Atoms on adjacent carbons are furthest apart.

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Eclipsed conformation

Atoms on adjacent carbons are closest together.

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Torsional strain

Strain from forcing non-bonded atoms close together.

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Cycloalkane angle strain

Strain from bond angles differing from ideal.

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Cyclopentane

A cycloalkane with five carbon atoms in a ring.

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IUPAC's prefix-infix-suffix system

A system for naming organic compounds: prefix indicates carbon atoms, infix indicates bond types and suffix indicates compound class.

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Cyclopentane Conformation

Cyclopentane puckers from a planar shape to reduce torsional strain, adopting an "envelope" conformation.

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Cyclohexane Conformation

Cyclohexane's most stable form is a chair conformation, minimizing strain by having all bond angles close to 109.5°.

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Axial vs. Equatorial Bonds (Cyclohexane)

In cyclohexane's chair form, bonds can be axial (parallel to ring axis) or equatorial (roughly perpendicular to ring axis).

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Boat Conformation (Cyclohexane)

A less stable cyclohexane conformation where carbons 1 and 4 are bent towards each other.

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Chair Conformation Interconversion

Two chair conformations of cyclohexane can change into one another through a boat-like transition state (intermediate).

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Methylcyclohexane Stability

A methyl group in a cyclohexane ring prefers an equatorial position in the chair conformation, leading to a difference in stability between chair forms.

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Cholestanol Ring Conformation

Cholestanol, a cholesterol relative, has multiple rings with varying shapes and conformations.

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Strain Energy in Cycloalkanes

Cycloalkanes exhibit different types of strain (angle, torsional, steric) when their carbons are forced to form closed ring structures.

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Alkane Density

Alkane liquids and solids typically have a density less than water, causing them to float.

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Heat of Combustion

The heat released when one mole of a substance is completely burned to carbon dioxide and water.

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Natural Gas Composition

Mostly methane (90-95%) and some ethane (5-10%).

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Constiutional Isomers

Different compounds with the same molecular formula but a different atomic arrangement.

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Synthesis Gas

A mixture of carbon monoxide and hydrogen used to make other chemicals.

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Cis-trans Isomers

Molecules with the same atoms and bonds but different spatial arrangements, not convertible by rotating single bonds.

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Cycloalkane Chair Conformations

Different 3D shapes of cycloalkane molecules, essential for understanding stability.

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Dispersion Forces

Weak attractions between molecules due to temporary dipoles.

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Boiling Point Alkanes

The temperature at which a liquid changes to a gas, influenced by a molecule's size and intermolecular forces.

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State of Alkanes (regarding BP)

Alkanes with fewer carbons are gases, more carbon atoms are liquids and very long chains are solids.

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Equatorial and Axial Positions (cyclohexane)

Describes the positions of substituents on a cyclohexane ring, which impact stability.

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Stability of Cis-trans Isomers (cyclohexane)

The relative stability of cis- and trans- isomers of substituted cyclohexane rings depends on relative position of substituents, axial vs. equatorial.

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Physical Properties of Alkanes

Alkanes are nonpolar, with only weak intermolecular forces which affect their boiling points and densities.

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Stability of cis and trans isomers

Trans isomers are generally more stable than cis isomers due to less steric strain between substituents, which are further apart in the trans configuration.

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Why are alkenes planar?

The carbon atoms in a double bond are sp2 hybridized, resulting in a trigonal planar geometry with bond angles approximately 120°.

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What are alkynes' structural features?

The carbon atoms in a triple bond are sp hybridized. One s bond with linear geometry and two p bonds form a triple bond, with a bond angle of 180°.

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What is the phenyl group?

The phenyl group is a benzene ring with one hydrogen atom removed, acting as a substituent in larger molecules.

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E,Z System Naming

A method used to name alkene isomers that considers the priority of groups attached to the double bond based on atomic number. If the highest priority groups are on the same side of the double bond, it's Z. If they are on opposite sides, it's E.

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Cycloalkene Double Bond

In cycloalkanes with small rings, the double bond is always cis due to the ring's size constraint. A trans double bond is not possible in smaller rings.

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Dienes, Trienes, and Polyenes

Alkenes with multiple double bonds are called dienes (2 double bonds), trienes (3 double bonds), and polyenes (many double bonds)

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Vitamin A Isomerism

Vitamin A is an example of a polyene; it has five double bonds, and four of them can exhibit cis-trans isomerism. Vitamin A is the all-trans isomer.

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Terminal Alkynes

Alkynes with the triple bond at the end of the carbon chain. Their hydrogen atom is acidic and can be removed by strong bases like sodium amide.

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Acidity of Terminal Alkynes

The acidity of terminal alkynes is a unique property. The hydrogen at the end of the carbon chain is acidic enough to be removed by strong bases, making them different from alkanes and alkenes.

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Alkynes' Structural Features

Alkynes are hydrocarbons with a triple bond between two carbon atoms. Each carbon atom in a triple bond is sp hybridized, resulting in a linear geometry with a bond angle of 180 degrees. This results in a very strong bond and a rigid linear structure.

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Terminal Alkyne Acidity

Terminal alkynes, where the triple bond is at the end of the carbon chain, are more acidic than alkanes or alkenes. This is due to the higher s-character of the sp-hybridized carbon in the terminal alkyne, which stabilizes the negative charge on the conjugate base, making it easier to remove a hydrogen atom.

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Alkenes: IUPAC Naming

Use the infix '-en-' to indicate a carbon-carbon double bond. Number the parent chain to give the first carbon of the double bond the lowest number. Follow IUPAC rules for substituents.

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Alkenes: Common Names

Some alkenes, especially small ones, are commonly known by their traditional names.

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Alkynes: IUPAC Naming

Use the infix '-yne-' to indicate a carbon-carbon triple bond. Number the parent chain to give the first carbon of the triple bond the lowest number. Follow IUPAC rules for substituents.

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E,Z Configuration: Priority

Priority is assigned based on the atomic number of substituents. Higher atomic number = higher priority.

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E,Z Configuration: Rules

If a tie in priorities exists, look at the next set of atoms attached to the double bond. Priority is assigned at the first point of difference.

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E,Z Configuration: Same Side

If the high-priority groups are on the same side of the double bond, the configuration is 'Z' (German: zusammen, together).

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E,Z Configuration: Opposite Side

If the high-priority groups are on opposite sides of the double bond, the configuration is 'E' (German: entgegen, opposite).

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Study Notes

Alkanes and Cycloalkanes

  • Hydrocarbon: A compound made up of only carbon and hydrogen.
  • Saturated hydrocarbon: A hydrocarbon with only single carbon-carbon bonds.
  • Alkane: A saturated hydrocarbon with carbon atoms arranged in an open chain.
  • Aliphatic hydrocarbon: Another name for an alkane.

Structure of Alkanes

  • Shape: Tetrahedral geometry (all carbons are sp³ hybridized). All bond angles are approximately 109.5°.

Representing Alkanes

  • Line-angle formula: An abbreviated way to draw structural formulas.
    • Each line represents a single bond.
    • Each line ending represents a CH₃ group.
    • Each vertex (angle) represents a carbon atom.

Alkanes - General Formula

  • Alkanes have the general formula CₙH₂ₙ₊₂

Constitutional Isomers

  • Constitutional isomers: Compounds with the same molecular formula but different connectivity of their atoms.

IUPAC Nomenclature

  • Suffix -ane: Specifies an alkane.
  • Prefix: Tells the number of carbon atoms.

IUPAC Nomenclature (continued)

  • Parent name: The longest carbon chain.
  • Substituent: A group bonded to the parent chain.
    • Alkyl group: A substituent derived by removing a hydrogen from an alkane; given the symbol R⁻. CH₄ becomes CH₃⁻ (methyl).

IUPAC Nomenclature (continued)

  • Listing substituents: -If there is one substituent, number the chain from the end that gives it the lower number.
    • If there are two or more identical substituents, number the parent chain from the end that gives the lower number to the substituent encountered first. The number of times a substituent occurs is indicated by di-, tri-, tetra-, and so on.
    • If there are two or more different substituents, list the substituents in alphabetical order. Number from the end of the longest chain that gives the substituent encountered first, the lower number. The prefixes (di, tri, tetra) are not included in alphabetical order. "Iso" (as in isopropyl) is included in alphabetizing.

Classification of Carbons

  • Primary (1°): A carbon bonded to one other carbon.
  • Secondary (2°): A carbon bonded to two other carbons.
  • Tertiary (3°): A carbon bonded to three other carbons.
  • Quaternary (4°): A carbon bonded to four other carbons.

Cycloalkanes

  • General formula: CₙH₂ₙ
  • Five- and six-membered rings are most common.
  • Structure and nomenclature:
    • Prefix the name of the corresponding open-chain alkane with "cyclo-".
    • Give a name and number to each substituent on the ring. -If only one substituent needs to be named, no need to number. -If two substituents need a number, number the ring from the substituent of lowest alphabetical order. -If three or more substituents are present, number to get the lowest set of numbers, and then list them alphabetically.

Cycloalkanes (continued)

  • Commonly written as line-angle formulas: Examples include isopropylcyclopentane, 1-tert-Butyl-4-methyl-cyclohexane, 1-Isobutyl-2-methyl-cyclohexane, 1-Ethyl-1-methyl-cyclopropane.

IUPAC- a general system

  • prefix-infix-suffix
    • Prefix: Tells the number of carbon atoms in the parent.
    • Infix: Tells the nature of the carbon-carbon bonds.
    • Suffix: Tells the class of the compound.

IUPAC - a general system (continued)

  • Examples: propene, ethanol, butanone, butanal, butanoic acid, cyclohexanol, ethyne, ethanamine.

Conformation

  • Conformation: Any three-dimensional arrangement of atoms in a molecule that results from rotation about a single bond.
  • Staggered conformation: A conformation about a carbon-carbon single bond where the atoms on one carbon are as far apart as possible from the atoms on an adjacent carbon.
  • Eclipsed conformation: A conformation about a carbon-carbon single bond where the atoms on one carbon are as close as possible to the atoms on an adjacent carbon.
  • Torsional strain: Strain that arises when nonbonded atoms separated by three bonds are forced from a staggered conformation to an eclipsed conformation, also called eclipsed interaction strain.
  • The lowest energy conformation of an alkane is a fully staggered conformation.

Cycloalkanes (cont'd)

  • Cyclopentane: In planar cyclopentane, all C-C-C bond angles are 108°, slightly different from the tetrahedral angle of 109.5°. Consequently, there is little angle strain.
  • Angle strain: Strain that arises when a bond angle is either compressed or expanded compared with its optimal value.
  • Cyclopentane (cont'd): In planar cyclopentane, there are 10 fully eclipsed C-H bonds. Puckering to an "envelope" conformation relieves part of this strain.

Cyclohexane

  • Chair conformation: The most stable conformation of cyclohexane. In a chair conformation, all bond angles are approximately 109.5°, and all bonds on adjacent carbons are staggered.
  • Chair cyclohexane: Six C-H bonds are equatorial, and six are axial.
  • Equatorial bond: Extends from the ring roughly perpendicular to the imaginary axis of the ring.
  • Axial bond: Extends from the ring roughly parallel to the imaginary axis of the ring.
  • Boat conformation: A puckered conformation in which carbons 1 and 4 are bent toward each other. A boat conformation is less stable than a chair conformation by 27 kJ/mol (6.5 kcal/mol).
  • Torsional strain: Created by four sets of eclipsed hydrogen interactions.
  • Steric strain: Created by one set of flagpole interactions.

Cyclohexane (continued)

  • Examples of commonly written line-angle formulas: isopropylcyclopentane, 1-tert-butyl-4-methyl-cyclohexane, 1-isobutyl-2-methyl-cyclohexane, 1-ethyl-1-methyl-cyclopropane

Cis-trans isomerism

  • Cis-trans isomers: Have the same molecular formula and the same connectivity of atoms but different arrangements of atoms in space that cannot be interconverted by rotation about sigma bonds.
  • Cyclopentane: A cyclopentane ring is commonly viewed through an edge or from above.
    • Examples: cis-1,2-dimethylcyclopentane, trans-1,2-dimethylcyclopentane.
  • Cyclohexane: A cyclohexane ring is commonly viewed as a planar hexagon viewed from the side or from above.
    • Examples: cis-1,4-dimethylcyclohexane, trans-1,4-dimethylcyclohexane.

Cis-trans isomerism (continued)

  • In viewing chair conformations, groups equatorial in one chair are axial in the alternative chair.
  • For trans-1,4-dimethylcyclohexane, the diequatorial chair is more stable than the diaxial chair.
  • For cis-1,4-dimethylcyclohexane, the alternative chairs are of equal stability.

Physical Properties

  • Alkanes are nonpolar compounds and have only weak interactions between their molecules.
  • Dispersion forces: Weak intermolecular forces of attraction resulting from temporary induced dipoles.
  • Boiling point: Low-molecular-weight alkanes are gases, higher-molecular-weight alkanes are liquids, and high-molecular-weight alkanes are solids.
  • Density: Alkanes have an average density of about 0.7 g/mL, and liquid and solid alkanes float on water.
  • Constitutional isomers: Different compounds with different physical properties.

Reactions of Alkanes

  • Oxidation: The basis for using alkanes as energy sources for heat and power.
  • Heat of combustion: The heat released when one mole of a substance is oxidized to carbon dioxide and water.

Sources of Alkanes

  • Natural gas: Primarily methane, with some ethane.
  • Petroleum: Gasses, naphthas, kerosene, fuel oil, lubricating oils, and asphalt.
  • Coal: A source for synthesis gas, which is a mixture of carbon monoxide and hydrogen.

Synthesis Gas

  • Synthesis gas: A mixture of carbon monoxide and hydrogen in varying proportions.

Methane Economy

  • If the United States moves from a petroleum economy to a natural gas economy, synthesis gas and synthesis gas-derived methanol will be key building blocks.

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Alkanes and Cycloalkanes PDF
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Description

Test your knowledge on alkanes, including their structural characteristics and proper nomenclature. This quiz covers topics such as conformation stability, classification of carbons, and IUPAC naming rules. Perfect for students studying organic chemistry or hydrocarbon compounds!

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