Hydrocarbons: Unit 9 Quiz
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Questions and Answers

What is the name for the general formula for alkanes?

CnH2n+2

The term 'hydrocarbon' is self-explanatory, meaning compounds containing only carbon and hydrogen.

True

What does the term "homologous series" refer to?

A series of organic compounds having the same functional group but differing by a CH2 unit.

What is the IUPAC name for C4H10?

<p>Butane.</p> Signup and view all the answers

Which of the following is the correct IUPAC name for the compound with the structural formula CH3CH2CH(CH3)CH2CH3?

<p>2-Methylpentane</p> Signup and view all the answers

Explain what an alkyl group is and provide an example.

<p>An alkyl group is derived from an alkane by removing one hydrogen atom. An example is the methyl group (-CH3).</p> Signup and view all the answers

Which of the following is the correct IUPAC name for the compound with the structural formula CH3CH2CH2CH(CH3)CH2CH(CH3)CH2CH3?

<p>4-Ethyl-2-methylheptane</p> Signup and view all the answers

What is the main source of alkanes?

<p>Petroleum and natural gas.</p> Signup and view all the answers

What is the general formula for alkynes?

<p>CnH2n-2.</p> Signup and view all the answers

What is the common name for ethyne?

<p>Acetylene.</p> Signup and view all the answers

Name the type of isomerism exhibited by the compounds CH3CH2C≡CH and CH3C≡CCH3.

<p>Position isomers.</p> Signup and view all the answers

What is the name for the process where alkenes are converted to alkanes by reaction with dihydrogen gas in presence of catalysts?

<p>Hydrogenation.</p> Signup and view all the answers

What is the name of the reaction that produces a higher alkane from an alkyl halide using sodium metal in anhydrous ether?

<p>Wurtz reaction.</p> Signup and view all the answers

What is the name of the reaction that involves the removal of a molecule of carbon dioxide from a carboxylic acid?

<p>Decarboxylation.</p> Signup and view all the answers

What is the name for the type of isomerism where the arrangement of atoms is different in space but the same atoms are connected to each other?

<p>Geometric isomerism or cis-trans isomerism.</p> Signup and view all the answers

What are the three main characteristics required for a system to be considered aromatic?

<p>Planarity, delocalization of π electrons, and presence of (4n + 2) π electrons in the ring (Hückel's rule).</p> Signup and view all the answers

What is the name of the reaction where benzene reacts with an alkyl halide in the presence of Lewis acid, such as AlCl3?

<p>Friedel-Crafts alkylation.</p> Signup and view all the answers

What is the name given to the process where a nitro group (-NO2) is introduced into a benzene ring?

<p>Nitration.</p> Signup and view all the answers

Alkynes are less acidic than alkanes.

<p>False</p> Signup and view all the answers

Name the key reaction that is used to distinguish between alkanes, alkenes, and alkynes and relies on the different reactivity of the hydrogen atoms in these compounds?

<p>Reaction with a strong base like sodium amide (NaNH2).</p> Signup and view all the answers

What is the name for the reaction that involves the addition of a water molecule across a triple bond, typically in the presence of a mercury catalyst and acid?

<p>Hydration of alkynes.</p> Signup and view all the answers

What is the name for the process where an alkene reacts with ozone to form an ozonide, which is further cleaved to smaller molecules by reaction with zinc and water?

<p>Ozonolysis.</p> Signup and view all the answers

What is the name for the process that involves the joining of many small molecules (monomers) to form a large molecule (polymer) under specific conditions like high temperature and pressure?

<p>Polymerization.</p> Signup and view all the answers

What is the common name for the compound with the molecular formula C6H6?

<p>Benzene.</p> Signup and view all the answers

What is the name given to compounds containing benzene rings, which are highly unsaturated and often have a pleasant aroma?

<p>Arenes.</p> Signup and view all the answers

Benzene's stability can be attributed to the presence of alternating double and single bonds within its ring structure.

<p>False</p> Signup and view all the answers

What is the name for the type of group attached to a benzene ring that directs further substitution to the ortho and para positions?

<p>Ortho-para directing group.</p> Signup and view all the answers

What is the name for the type of group attached to a benzene ring that directs further substitution to the meta position?

<p>Meta-directing group.</p> Signup and view all the answers

Which of the following is NOT a carcinogenic hydrocarbon?

<p>Cyclohexane</p> Signup and view all the answers

The Wurtz reaction is a preferred method for preparing alkanes containing an odd number of carbon atoms.

<p>False</p> Signup and view all the answers

Study Notes

Hydrocarbons: Unit 9

  • Hydrocarbons are compounds containing only carbon and hydrogen.
  • They are important energy sources and industrial materials.
  • Various types exist: alkanes, alkenes, alkynes, and aromatic hydrocarbons.
  • Alkanes are saturated hydrocarbons (single bonds) with the general formula CnH2n+2.
  • Alkenes are unsaturated hydrocarbons (contain double bonds) with the general formula CnH2n.
  • Alkynes are unsaturated hydrocarbons (contain triple bonds) with the general formula CnH2n-2.
  • Aromatic hydrocarbons contain a benzene ring, a cyclic structure with delocalized pi electrons.

Objectives

  • Name various hydrocarbons using IUPAC nomenclature.
  • Recognize/draw structures of hydrocarbon isomers.
  • Understand different methods for hydrocarbon preparation.
  • Differentiate between hydrocarbon classes based on properties.
  • Comprehend conformations of ethane.
  • Analyze the industrial and energy roles of hydrocarbons.
  • Predict addition products of alkenes/alkynes.
  • Understand benzene structure, aromaticity, and electrophilic substitution reactions.
  • Identify and understand carcinogenicity and toxicity.

Classification

  • Hydrocarbons are categorized based on the type of carbon-carbon bonds: saturated, unsaturated, and aromatic.
  • Saturated hydrocarbons contain only single bonds.
  • Unsaturated hydrocarbons contain double or triple bonds.
  • Aromatic hydrocarbons have a characteristic cyclic structure with delocalized electrons.

Alkanes

  • Alkanes are saturated hydrocarbons.
  • Methane (CH₄) is the simplest alkane.
  • Alkanes exhibit structural (chain) isomerism.
  • Boiling point generally increases with increasing molecular mass.
  • Alkanes are relatively inert under normal conditions.

Nomenclature and Isomerism

  • IUPAC nomenclature systems provide unique names for each hydrocarbon.
  • Structural isomers are molecules with the same molecular formula but different structures and the resulting differing physical properties.
  • Branched chain isomers are a type of structural isomer.
  • Isomers exist for a given molecular formula, and the more complex the molecule the more isomer variations exist.

Preparation of Alkanes

  • Alkanes are commonly prepared from unsaturated hydrocarbons through hydrogenation.
  • Alkyl halides can be reacted with zinc or sodium to produce alkanes.
  • Carboxylic acids can be converted to alkanes via decarboxylation.

Physical Properties of Alkanes

  • Generally non-polar, non aqueous solubility (like dissolves like).
  • Weak intermolecular forces (van der Waals).
  • Low melting/boiling point compared to similar sized molecules.
  • Increasing molecular mass leads to higher melting/boiling points.

Chemical Properties of Alkanes

  • Relatively inert towards most reagents.
  • Undergo substitution reactions (particularly chlorination with light/heat).
  • Undergo combustion reactions to form carbon dioxide and water releasing energy.

Alkenes

  • Alkenes contain carbon-carbon double bonds.
  • Unsaturated hydrocarbons.
  • The general formula is CnH2n.
  • Exhibit structural and geometric (cis-trans) isomerism.
  • Can undergo addition reactions (with hydrogen, halogens, water etc.).

Alkynes

  • Alkynes contain carbon-carbon triple bonds.
  • Unsaturated hydrocarbons.
  • The general formula is CnH2n-2.
  • Exhibit structural isomers.
  • Undergo addition reactions but are more acidic than alkanes and alkenes.

Aromatic Hydrocarbons

  • Contain a benzene ring.
  • Highly stable due to resonance.
  • Undergo electrophilic substitution reactions.
  • Examples include benzene, toluene, and naphthalene.

Benzene

  • A cyclic unsaturated hydrocarbon.
  • A planar six-membered ring structure with delocalized pi electrons.
  • Exhibit unusual stability due to resonance.
  • Undergo electrophilic substitution reactions.

Addition Reactions

  • Addition reactions break the multiple bonds (double or triple).
  • Add elements to the double or triple bond.
  • Common with both alkenes and alkynes.
  • Common addition reactions include: halogenation, hydration, hydrogenation.

Physical Properties

  • Generally non-polar.
  • Lower boiling points compared to similar sized molecules.
  • Insoluble in water.
  • Soluble in organic solvents.

Chemical Properties

  • Alkenes display addition reactions when reacting with halogens, hydrogen, water etc.
  • Addition products can differ depending upon the reaction conditions/reagents.
  • Common electrophilic addition reactions.
  • Addition of hydrogen halides (Markovnikov’s Rule - and peroxide effect)
  • Addition reactions break the multiple bonds; add atoms to the multiple bonds.

Summary

  • Hydrocarbon classifications (alkanes, alkenes, alkynes, aromatic).
  • Properties and reactions of each class.
  • Common reactions like hydrogenation, halogenation, and combustion, and specific reactions like oxidation, ozonolysis, and polymerisation.

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Test your knowledge on hydrocarbons with this quiz. Explore the different types of hydrocarbons including alkanes, alkenes, alkynes, and aromatic hydrocarbons. You'll also cover nomenclature, isomers, preparation methods, and their roles in industry and energy.

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