CHM132 Exam 1 Study Guide: Hydrocarbons, Alcohols, Aldehydes & Ketones

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CH12: Hydrocarbons

Organic Compounds: Shape and Bonds Around Carbon

Organic compounds are molecules primarily composed of carbon and hydrogen, often with oxygen, nitrogen, or other elements. The bonding and geometry of carbon atoms are fundamental to organic chemistry.

Carbon Bonding: Carbon forms four covalent bonds, resulting in tetrahedral geometry (bond angle ≈ 109.5°).
Types of Hydrocarbons: Alkanes (single bonds), Alkenes (double bonds), Alkynes (triple bonds).
Hybridization: sp3 (alkanes), sp2 (alkenes), sp (alkynes).
Example: Methane (CH4) is an alkane with tetrahedral geometry.

IUPAC Nomenclature of Alkanes, Alkenes, Alkynes with Substituents

The International Union of Pure and Applied Chemistry (IUPAC) system provides rules for naming organic compounds.

Alkanes: Name based on longest carbon chain; substituents are named as prefixes.
Alkenes/Alkynes: Number chain to give double/triple bond lowest possible number.
Substituents: Alkyl groups (e.g., methyl, ethyl) are listed alphabetically.
Example: 2-methylpentane, 3-hexene, 2-butyne.

Drawing Expanded, Condensed, and Line-Angle Structures

Organic molecules can be represented in several ways:

Expanded: Shows all atoms and bonds.
Condensed: Groups atoms (e.g., CH3CH2CH3).
Line-Angle: Lines represent bonds; vertices represent carbon atoms.
Example: Propane: Expanded (H3C–CH2–CH3), Condensed (CH3CH2CH3), Line-angle (three connected lines).

Properties of Hydrocarbons

Hydrocarbons exhibit characteristic physical properties:

Boiling Points: Increase with molecular size; decrease with branching.
Physical States: Small alkanes are gases; larger ones are liquids or solids.
Solubility: Nonpolar; insoluble in water, soluble in nonpolar solvents.
Polarity: Hydrocarbons are nonpolar.
Example: Pentane is a liquid at room temperature, insoluble in water.

Cis-Trans Isomers and Structural Isomers

Isomers are compounds with the same formula but different structures.

Structural Isomers: Differ in connectivity of atoms.
Cis-Trans Isomers: Occur in alkenes; cis (same side), trans (opposite sides) of double bond.
Example: 2-butene: cis-2-butene vs. trans-2-butene.

Naming Cyclic Alkanes and Alkenes; Drawing Structures

Cyclic hydrocarbons are ring-shaped molecules.

Cyclic Alkanes: Prefix "cyclo-" + alkane name (e.g., cyclopentane).
Cyclic Alkenes: Number ring to give double bond lowest number.
Drawing: Line-angle structures are common for rings.
Example: Cyclohexane (hexagon), cyclohexene (hexagon with double bond).

Aromatic Compounds (Benzene)

Aromatic compounds contain benzene rings, characterized by delocalized electrons.

Benzene: C6H6, six-membered ring with alternating double bonds.
Stability: Aromaticity provides extra stability.
Example: Benzene, toluene, phenol.

Naming Substituted Aromatic Compounds

Substituted aromatics are named based on the functional group and position.

Common Names: Aniline (amino group), phenol (hydroxyl group), toluene (methyl group).
Position: ortho (1,2), meta (1,3), para (1,4) positions.
Example: para-nitrotoluene (NO2 at position 4 of toluene).

Addition Reactions of Alkenes

Alkenes undergo addition reactions, where atoms add across the double bond.

Hydrogenation: Addition of H2 (requires catalyst, e.g., Pt).
Hydration: Addition of H2O (acid catalyst).
Polymerization: Formation of polymers from monomers (e.g., ethylene to polyethylene).
Conditions: Specific reagents and catalysts required.
Example: Ethene + H2 → Ethane (hydrogenation).

CH13: Alcohols, Phenols, Thiols, and Ethers

Definitions and Structures

These compounds contain oxygen or sulfur functional groups attached to hydrocarbons.

Alcohols: Contain –OH group attached to carbon.
Phenols: –OH group attached to aromatic ring.
Thiols: Contain –SH group.
Ethers: Oxygen atom connects two alkyl or aryl groups (R–O–R').
Example: Ethanol (alcohol), phenol, ethanethiol (thiol), diethyl ether (ether).

Properties: Boiling Points, Solubilities, Polarity

Physical properties depend on functional groups and molecular structure.

Boiling Points: Alcohols > ethers > hydrocarbons (due to hydrogen bonding).
Solubility: Alcohols and phenols are soluble in water; ethers less so; thiols are less polar.
Polarity: Alcohols and phenols are polar; ethers are moderately polar; thiols are less polar.
Example: Methanol is highly soluble in water; diethyl ether is less soluble.

IUPAC Nomenclature of Alcohols, Phenols, Thiols, and Ethers

Systematic naming follows IUPAC rules:

Alcohols: Replace "-e" with "-ol" (e.g., ethanol).
Phenols: Named as derivatives of phenol.
Thiols: Add "thiol" suffix (e.g., ethanethiol).
Ethers: Name alkyl groups + "ether" (e.g., methyl ethyl ether).
Example: 2-propanol, 4-methylphenol, 1-butanethiol, dimethyl ether.

Reactions of Alcohols: Dehydration, Oxidation, Combustion

Alcohols undergo several important reactions:

Dehydration: Removal of water to form alkenes (acid catalyst).
Oxidation: Primary alcohols → aldehydes → carboxylic acids; secondary alcohols → ketones; tertiary alcohols do not oxidize easily.
Combustion: Complete oxidation to CO2 and H2O.
Example: Ethanol dehydration forms ethene; oxidation forms acetaldehyde.

Major/Minor Products from Reactions

Reactions may yield multiple products; the major product is typically favored by reaction conditions.

Dehydration: Follows Zaitsev's rule; more substituted alkene is major product.
Example: 2-butanol dehydration yields 2-butene (major) and 1-butene (minor).

Alcohol Classification (1°, 2°, 3°)

Alcohols are classified by the number of carbon atoms attached to the carbon bearing the –OH group.

Primary (1°): –OH on carbon attached to one other carbon.
Secondary (2°): –OH on carbon attached to two other carbons.
Tertiary (3°): –OH on carbon attached to three other carbons.
Example: Ethanol (1°), isopropanol (2°), tert-butanol (3°).

Comparing Boiling Points and Solubilities of Alcohols with Hydrocarbons

Alcohols have higher boiling points and solubilities than hydrocarbons due to hydrogen bonding.

Boiling Point: Alcohols > hydrocarbons of similar size.
Solubility: Alcohols are more soluble in water.
Example: Ethanol (alcohol) vs. ethane (hydrocarbon).

CH14: Aldehydes & Ketones

Definitions: Aldehydes & Ketones

Aldehydes and ketones are carbonyl compounds with distinct structures and properties.

Aldehydes: Carbonyl group (C=O) at end of carbon chain.
Ketones: Carbonyl group (C=O) within carbon chain.
Example: Formaldehyde (aldehyde), acetone (ketone).

Nomenclature of Aldehydes & Ketones

IUPAC naming rules for carbonyl compounds:

Aldehydes: Replace "-e" with "-al" (e.g., ethanal).
Ketones: Replace "-e" with "-one" (e.g., propanone).
Example: Butanal (aldehyde), 2-pentanone (ketone).

Identifying Aldehydes from Ketones: Tollens’ and Benedict’s Tests

Chemical tests distinguish aldehydes from ketones.

Tollens’ Test: Aldehydes reduce Ag+ to metallic silver; ketones do not react.
Benedict’s Test: Aldehydes reduce Cu2+ to red Cu2O; ketones do not react.
Example: Glucose (aldehyde) gives positive Benedict’s test.

Reduction Reactions of Aldehydes

Aldehydes can be reduced to primary alcohols.

Reagents: Hydrogen (H2) with catalyst, or NaBH4/LiAlH4.
Conditions: Mild heating, solvent.
Equation:
Example: Ethanal reduced to ethanol.

Oxidation Reactions of Aldehydes

Aldehydes can be oxidized to carboxylic acids.

Reagents: KMnO4, K2Cr2O7, or other oxidizing agents.
Equation:
Example: Ethanal oxidized to ethanoic acid.

Reactions of Aldehydes and Ketones with Alcohols

Carbonyl compounds react with alcohols to form hemiacetals and acetals.

Hemiacetal Formation: Aldehyde/ketone + alcohol → hemiacetal.
Acetal Formation: Hemiacetal + alcohol → acetal (acid catalyst).
Equation: (hemiacetal)
Example: Acetaldehyde + ethanol forms an acetal.

Physical Properties of Aldehydes & Ketones

Physical properties are influenced by the carbonyl group.

Boiling Points: Higher than hydrocarbons, lower than alcohols.
Solubility: Small aldehydes and ketones are soluble in water.
Example: Acetone is miscible with water; butanone is less so.

Compound Type	Functional Group	Boiling Point (relative)	Water Solubility
Hydrocarbon	None	Low	Poor
Alcohol	–OH	High	Good
Aldehyde	–CHO	Moderate	Good (small molecules)
Ketone	–CO–	Moderate	Good (small molecules)
Ether	R–O–R'	Lower than alcohol	Moderate
Thiols	–SH	Low	Poor

Additional info: Academic context and examples were added to expand brief points into full explanations and to make the notes self-contained for exam preparation.