Organic Chemistry: Alcohols and Hydrocarbons

Organic Chemistry Overview

• Organic chemistry is the study of organic compounds
• Organic compounds contain carbon, hydrogen, and sometimes other elements
• The term "organic" relates to the importance of carbon compounds in living systems
• Aspirin has the formula C₉H₈O₄

Representations of Organic Molecules

• Carbon can make 4 bonds
• Carbon bonds to other carbon atoms to form long chains or rings with hydrogen atoms (or other atoms) attached
• Carbon bonds to other carbon atoms in single, double, or triple bonds
• Ball-and-stick models, molecular formulas, structural formulas, condensed structural formulas, and line structures are used to represent organic molecules

Formulas and Structures: Octane Example

• Ball-and-stick model, Molecular formula: C₈H₁₈
• Structural formula: CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₃
• Condensed structural formula: CH₃(CH₂)₆CH₃
• Line structure
• Perspective drawing

Activity: Drawing a Structural Formula/Line Structure

• A structural formula shows bonds as lines and labels the atoms
• The structural formula for aspirin is shown

Activity: Drawing a Line Structure

• The line drawing shows only bonds between carbon atoms and functional groups
• Functional groups are labeled

Functional Groups

• A reactive part of a molecule that undergoes characteristic reactions
• Often an attachment to the carbon-hydrogen chain
• Organic compounds are classified by their functional groups

Functional Groups in Organic Molecules–Table

• Alkane, Functional Group–C-C-, Example Structure–CH₃CH₂CH₃, Example Name–propane, Example Property–heating fuel
• Alkene, Functional Group–C=C-, Example Structure–CH₃CH=CH₂, Example Name–propene, Example Property–used to form polypropylene, a stiff plastic
• Alkene, Functional Group–C≡C-, Example Structure–CH₃C≡CH, Example Name–propyne, Example Property–explosive in air
• Alcohol, Functional Group–-OH, Example Structure–CH₃CH₂CH₂OH, Example Name–propanol, Example Property–alcoholic and slightly stupefying odor
• Ether, Functional Group–-O-, Example Structure–CH₃CH₂CH₂OCH₃, Example Name–methyl propyl ether Example Property–anesthetic
• Ketone, Functional Group– −(C−O)−, Example Structure–CH₃COCH₃, Example Name–acetone, Example Property–good solvent; fingernail polish remover
• Aldehyde, Functional Group– −CHO, Example Structure–CH₃CH₂CHO, Example Name–propanal, Example Property–suffocating odor
• Carboxylic Acid, Functional Group– −COOH , Example Structure–CH₃CH₂CO₂H, Example Name–propanoic acid, Example Property–odor and flavor of Swiss cheese
• Ester, Functional Group– −COO−, Example Structure–CH₃CH₂CO₂CH₃, Example Name–methyl propanoate, Example Property–flavoring agent; fruity rum odor
• Amine, Functional Group– −NH₂, Example Structure–CH₃CH₂CH₂NH₂, Example Name–propylamine, Example Property–strong ammonia odor

Activity: Functional Groups

• Identifying the functional group from provided molecular formulas
• Example answers: CH₃OH (alcohol), (CH₃)₂CO (ketone), CH₃CH₂CO₂H (carboxylic acid), CH₃CH₂NH₂ (amine), CH₃CH₂CHO (aldehyde), CH₃CO₂CH2CH₃ (ester)

Hydrocarbons

• A carbon compound containing only carbon and hydrogen
• Hydrocarbons can form isomers
• Two compounds that have the same composition and formula but different arrangements of atoms in their molecular structures are called isomers

Acyclic Hydrocarbons

• A hydrocarbon that forms an open chain
• Bonding electrons are localized (confined to two adjacent atoms)
• Aliphatic hydrocarbons(hydrocarbons with localized bonds)
• Two kinds of aliphatic hydrocarbons: saturated and unsaturated

Saturated and Unsaturated Hydrocarbons

• Saturated hydrocarbon: Contains only single bonds between carbon atoms, all carbons are bonded to 4 other atoms. Also called alkanes
• Unsaturated hydrocarbon: Contains one or more double or triple bonds between carbon atoms
• Hydrocarbons with double bonds are called alkenes.
• Hydrocarbons with triple bonds are called alkynes

Which is Saturated

• Diagrams of alkane, alkene, and alkyne structures

Classification of Hydrocarbons

• Hierarchical diagram of hydrocarbon classifications (acyclic, cyclic; saturated, unsaturated; aromatic)

Cyclic Hydrocarbons

• Form a closed chain or ring of carbon atoms
• Aromatic compounds:
  • Cyclic molecules with carbon atoms attached in alternating single and double bonds
  • Electrons are delocalized (spread out over the entire ring structure)
  • Examples: cycloalkane, aromatic hydrocarbon

Petroleum

• A primary source of hydrocarbons
• Major use: energy production
• Usually found in one of two forms (natural gas and crude oil)
• Natural gas: used mainly for cooking and heating
• Crude oil: Must be refined before use

Refining Crude Oil

• Involves fractional distillation
• Separation of petroleum into fractions having different boiling points
• Results of fractional distillation are in a table
• Differences in boiling points due to intermolecular forces between hydrocarbon molecules
• Catalytic cracking: Uses heat and a catalyst to break down higher-boiling "gas oil" fraction, used to make gasoline

Petroleum Fractions–Table

• Listing of petroleum fractions: Names, boiling ranges, composition ranges, and uses
  • Fraction, Boiling Range, Composition Range (e.g., CH₄ to C₄H₁₀), Uses

Acyclic Hydrocarbons

• Three classes: Alkanes, alkenes, alkynes
• May be straight-chained or branched
• Alkanes are saturated, while alkenes and alkynes are unsaturated

Alkanes

• Saturated hydrocarbons with the general formula CₙH₂ₙ₊₂
• Value of n = 1-4, alkanes are gases; n = 5-18, liquids; n ≥ 18, solids
• Melting and boiling points increase with increasing number of carbon atoms
• Straight-chain alkanes have higher boiling points than branched alkanes

Boiling Point Trends

• Graph of boiling point vs. number of carbon atoms for alkanes

Boiling Points of Straight-chain Alkanes versus Branched-chain Alkanes

• Straight-chain alkanes have more surface contact between molecules, leading to higher boiling points than branched-chain alkanes

Patterns in Alkane Names–Table

• Table of alkane names and formulas

How to Name Alkanes

• Alkanes are named with a prefix denoting the number of atoms in the longest chain followed by the ending -ane
• Straight-chain (normal) alkanes have no branches
• Branched-chain alkanes are isomers of straight-chain alkanes, and their branches must be named separately

Formulas and Names of Some Alkanes–Table

• Table of structural formulas and names of various alkanes

Activity: Names of Alkanes With a Single Branch

• IUPAC name for isobutane

Activity Solution: Names of Alkanes With a Single Branch

• IUPAC names for specific branched-chain alkanes

Alkyl Groups

• An alkyl group is derived from an alkane by removal of 1 hydrogen atom, with a general formula CₙH₂ₙ₊₁
• Alkyl group names are similar to alkane names, except the -ane ending replaced by -yl
• If there is more than one of the same branch, use prefixes (di-, tri-)
• If more than one different branch, number them and list alphabetically

Activity: Names of Alkanes with Multiple Branches

• Naming a specific isomer of C₁₀H₂₂

Activity Solution: Names of Alkanes with Multiple Branches

• IUPAC name for a specific branched-chain alkane

Activity: Structural Formulas from Names of Alkanes

• Drawing the structural formula for 2,2,3-trimethylpentane

Activity Solution: Structural Formulas from Names of Alkanes

• Drawing the structural formula for 2,2,3-trimethylpentane

Reactions of Alkanes

• Alkanes don't react readily but heat or light provides energy for reactions
• Alkanes undergo catalytic cracking(longer hydrocarbon chains break to form shorter hydrocarbon molecules) and oxidation in exothermic combustion reactions (like C₃H₈ + 5O₂ → 3CO₂ + 4H₂O) and reaction with halogens (like C₆H₁₄ + Br₂ → C₆H₁₃Br + HBr)

Reaction of Hexane with Bromine

• Hexane reacts with bromine in presence of light to form colorless products, showing a substitution reaction
• Equation is presented

Alkenes

• Generally obtained from petroleum through the cracking of alkanes using heat and a catalyst.
• React to form polymers

Alkene Structure and Nomenclature

• Contain at least one C=C double bond.
• With just one double bond, the general formula is CₙH₂ₙ
• Alkenes named using the alkane root with the ending -ene replacing -ane
• Multiple double bonds can occur.

Formulas and Names of Some Alkenes–Table

• Table of structural formulas and names of various alkenes

Activity: Naming Alkenes

• Name a provided alkene structure

Activity Solution: Naming Alkenes

• IUPAC name for a specific alkene

Geometric Isomers

• Unlike alkanes (free rotation), groups attached to double bonded carbons are fixed
• Two different groups have to be attached to each of the double-bond carbon atoms to have cis and trans isomers
• Cis isomers means both groups are on the same side
• Trans isomers means both groups are on opposite sides

Cis and Trans Isomers

• Cis-2-butene and trans-2-butene isomers are presented
• Property differences (e.g., boiling points)
• Line structures are shown

Activity: Cis and Trans Isomers

• Determining whether molecules have cis and trans isomers and drawing structures

Activity Solution: Cis and Trans Isomers

• Determining if the provided molecules have cis and trans isomers.

Alkynes

• Contain a C≡C triple bond and have the general formula CₙH₂ₙ₋₂
• Named similarly to alkenes, using the alkane root with the ending -yne
• Do not have geometric isomers

Reactions of Alkenes and Alkynes

• Addition reaction: One in which extra atoms or groups are added across the double/triple bond
• Polymerization: Small molecules containing double bonds combine to form larger molecules with repeating units (monomers)

Some Products Made from Polymers

• Images of various products formed from polymers

Alkenes and Alkynes Combustion

• Alkenes and alkynes also undergo combustion reactions, for example C₂H₂ + 2.5O₂ → 2CO₂ + H₂O

Activity: Reactions of Alkenes and Alkynes

• Equation for a reaction between 2-butene and HBr

Cyclic Hydrocarbons

• Cycloalkanes contain carbon ring and are saturated hydrocarbons with general formula CₙH₂ₙ
• Cycloalkenes contain carbon ring and are unsaturated hydrocarbons with at least one double bond

Aromatic Hydrocarbons

• Electrons in double bonds spread out (delocalized) over entire ring structure
• Delocalization of electrons creates extra stability and less reactivity (aromatic character)
• Aromatic compounds are common in biological systems and drugs

Aromatic Hydrocarbons: Benzene

• Two Lewis structures can be written for benzene, giving rise to resonance
• Simplified structure using a circle to represent delocalized double bonds

Some Formulas and Names of Aromatic Hydrocarbons–Table

• Table of aromatic hydrocarbon names and formulas

Activity: Naming Aromatic Hydrocarbons

• Name a provided aromatic hydrocarbon structure

Activity Solution: Naming Aromatic Hydrocarbons

• IUPAC name for the given aromatic compound structure

Activity: Name Another Aromatic Hydrocarbon

• Name a given aromatic hydrocarbon containing an OH functional group and a Br substituent

Activity Solution: Name Another Aromatic Hydrocarbon

• IUPAC name for the given aromatic hydrocarbon structure

Alcohols and Ethers

Alcohols

• Characterized by the hydroxyl functional group (-OH)
• Polar molecules participating in hydrogen bonding
• Short-chain alcohols are water soluble, solubility decreases with chain length
• Have significantly higher boiling points than alkanes of comparable mass

Alcohols–Table

• Table of alcohol structural formulas and names

Activity: Names of Alcohols

• Name a given alcohol structure

Activity Solution: Names of Alcohols

• IUPAC name for a given alcohol structure

Ethers

• Organic molecule with an oxygen atom bonded to two carbon atoms
• R-O-R' structure, R notation represents hydrocarbon portion
• Polar molecules; higher boiling points than alkanes with comparable mass
• More volatile than alcohols; lower boiling points than alcohols with comparable mass

Naming Ethers

• Names of ethers include the names of attached alkyl groups in alphabetical order followed by "ether"

Aldehydes and Ketones

• Aldehydes: Contain carbonyl (-C=O) group and at least one hydrogen attached to carbon
• General formula R-CHO
• Oxidation product of an alcohol
• Common Examples: Formaldehyde (R=H) and Acetaldehyde (R=CH₃)
• Ketones: Contain carbonyl group (-C=O)
• General form R-C(=O)-R'
• Simplest and most important ketone is acetone (propanone)

Carboxylic Acids and Esters

• Carboxylic acids: Functional group of a carboxylic acid is a carbon atom double-bonded to an oxygen and singly-bonded to an -OH group
• Most common is acetic acid, also called ethanoic acid
• Typically weak acids; reactions involve loss of H⁺ (e.g., CH₃COOH)
• Esters: Contain a carbon atom double-bonded to an oxygen and singly-bonded to another oxygen which is bonded to another carbon group
• General formula RCO₂R'
• Most esters are volatile liquids with pleasant odors and flavors
• Formed through a condensation reaction of a carboxylic acid with an alcohol

Triglycerides

• Esters formed from glycerol and high molar mass carboxylic acids
• Glycerol reacts with carboxylic acids to form a triglyceride (esters)
• Whether it is a liquid oil or solid fat depends on the number of double bonds in the alkyl group (fatty acid)
• Saturated triglycerides are solids (e.g., fat) with no double bonds
• Unsaturated triglycerides are oils with many double bonds

Reactions of Triglycerides

• Hydrogenation: Converting oils to fats
• Saponification (making soaps): Opposite of esterification
  • Ester reacts with NaOH (in presence of heat) to form soap (salt) and glycerol

Amines

• Derivatives of ammonia (NH₃) with one or more hydrogen atoms replaced by organic groups
• Act as bases in chemical reactions
• Have a disagreeable fishy smell
• Common Examples: Caffeine and Nicotine

Organic Nomenclature

• Rules for naming different classes of organic compounds

Test your knowledge on the properties and nomenclature of alcohols and hydrocarbons. This quiz covers key concepts like functional groups, structural formulas, and branching in organic compounds. Perfect for chemistry students focusing on organic chemistry topics.