Alcohols, Phenols, Thiols, Ethers, Aldehydes, Ketones, and Functional Groups: Study Guide for CHEM 120 Exam 2

Chapter 13: Alcohols, Phenols, Thiols, and Ethers

Naming Alcohols, Phenols, Ethers, and Thiols

Organic compounds containing oxygen and sulfur are classified based on their functional groups. Proper naming follows IUPAC rules.

• Alcohols: Contain a hydroxyl group (-OH) attached to a carbon atom. Named by replacing the -e ending of the parent alkane with -ol. Number the chain to give the -OH group the lowest possible number.

• Phenols: Have a hydroxyl group attached to a benzene ring. Named as derivatives of phenol.

• Ethers: Contain an oxygen atom connected to two alkyl or aryl groups (R-O-R'). Named by listing the alkyl groups alphabetically followed by "ether" (common names).

• Thiols: Contain a sulfhydryl group (-SH). Named by adding "thiol" to the parent hydrocarbon name.

Example: 2-propanol (isopropyl alcohol), methyl ethyl ether, benzene thiol.

Identifying Primary, Secondary, and Tertiary Alcohols

Alcohols are classified based on the number of carbon atoms attached to the carbon bearing the -OH group.

• Primary (1°) Alcohol: The -OH group is attached to a carbon bonded to one other carbon.

• Secondary (2°) Alcohol: The -OH group is attached to a carbon bonded to two other carbons.

• Tertiary (3°) Alcohol: The -OH group is attached to a carbon bonded to three other carbons.

Example: Ethanol is a primary alcohol; isopropanol is a secondary alcohol.

Properties of Alcohols

Alcohols exhibit unique physical and chemical properties due to the presence of the hydroxyl group.

• Hydrogen bonding: Alcohols can form hydrogen bonds, leading to higher boiling points compared to alkanes.

• Solubility: Lower alcohols are soluble in water; solubility decreases with increasing carbon chain length.

• Acidity: Alcohols are weak acids.

Example: Methanol and ethanol are miscible with water.

Identifying Phenols, Thiols, and Ethers

Recognition of these functional groups is essential for classification and reactivity prediction.

• Phenol: Benzene ring with an -OH group.

• Thiols: Alkyl or aryl group with an -SH group.

• Ethers: Oxygen atom between two carbon groups.

Example: Phenol (C6H5OH), ethanethiol (C2H5SH), diethyl ether (C2H5-O-C2H5).

Properties of Phenols, Thiols, and Ethers

• Phenols: More acidic than alcohols; can form hydrogen bonds; antiseptic properties.

• Thiols: Lower boiling points than alcohols; strong odors; less hydrogen bonding.

• Ethers: Relatively inert; lower boiling points than alcohols; used as solvents.

Example: Phenol is used in disinfectants; diethyl ether is used as an anesthetic.

Reactions of Alcohols

Alcohols undergo several important reactions:

• Oxidation: Primary alcohols oxidize to aldehydes, then to carboxylic acids; secondary alcohols to ketones; tertiary alcohols resist oxidation.

• Dehydration: Removal of water to form alkenes.

• Esterification: Reaction with carboxylic acids to form esters.

Example: Oxidation of ethanol to acetaldehyde.

Equation:

$\mathrm{CH_3CH_2OH\ \xrightarrow{[O]}\ CH_3CHO\ \xrightarrow{[O]}\ CH_3COOH}$

Chapter 14: Aldehydes and Ketones

Identifying Aldehydes and Ketones

Aldehydes and ketones are carbonyl compounds distinguished by the placement of the carbonyl group.

• Aldehyde: Carbonyl group (C=O) at the end of a carbon chain.

• Ketone: Carbonyl group within the carbon chain (not at the end).

Example: Formaldehyde (aldehyde), acetone (ketone).

Naming Aldehydes and Ketones

Follow IUPAC rules for naming:

• Aldehydes: Replace the -e ending of the parent alkane with -al.

• Ketones: Replace the -e ending with -one; number the chain to give the carbonyl group the lowest number.

Example: Propanal (aldehyde), 2-butanone (ketone).

Properties of Aldehydes and Ketones

• Boiling points: Higher than alkanes, lower than alcohols due to dipole-dipole interactions.

• Solubility: Lower members are soluble in water.

• Odor: Many have distinctive odors.

Example: Acetone is miscible with water and used as a solvent.

Chemical Reactions: Oxidation and Reduction (Including Tollens’ Test)

• Oxidation: Aldehydes can be oxidized to carboxylic acids; ketones generally resist oxidation.

• Reduction: Both aldehydes and ketones can be reduced to alcohols.

• Tollens’ Test: Used to distinguish aldehydes from ketones; aldehydes react to form a silver mirror, ketones do not.

Equation:

$\mathrm{RCHO\ +\ [O]\ \rightarrow\ RCOOH}$

$\mathrm{R_2C=O\ +\ [H]\ \rightarrow\ R_2CH-OH}$

Addition Reactions: Hemiacetal/Hemiketal and Acetal/Ketal Formation

Aldehydes and ketones react with alcohols to form hemiacetals/hemiketals and then acetals/ketals.

• Hemiacetal: Formed from aldehyde + alcohol.

• Hemiketal: Formed from ketone + alcohol.

• Acetal/Ketal: Formed from hemiacetal/hemiketal + alcohol.

Equation:

$\mathrm{RCHO\ +\ R'OH\ \rightarrow\ RCH(OH)OR'}$ (hemiacetal)

$\mathrm{R_2C=O\ +\ R'OH\ \rightarrow\ R_2C(OH)OR'}$ (hemiketal)

Comparing Boiling Points of Organic Compounds

Boiling points depend on intermolecular forces present in the compound.

• Alcohols: Highest boiling points due to hydrogen bonding.

• Aldehydes/Ketones: Intermediate boiling points due to dipole-dipole interactions.

• Ethers: Lower boiling points; lack hydrogen bonding.

• Alkanes: Lowest boiling points; only London dispersion forces.

Example: Ethanol boils at 78°C, diethyl ether at 34.6°C, propane at -42°C.

Forces Found in Organic Compounds

Intermolecular forces determine physical properties.

• Hydrogen bonding: Strongest; found in alcohols and phenols.

• Dipole-dipole: Found in aldehydes, ketones, ethers.

• London dispersion: Weakest; present in all molecules, especially alkanes.

Example: Water (hydrogen bonding), acetone (dipole-dipole), methane (London dispersion).

Cumulative Topics

Identifying Functional Groups of Organic Compounds

Functional groups are specific groups of atoms within molecules that determine chemical reactivity.

• Alcohol: -OH

• Aldehyde: -CHO

• Ketone: -CO-

• Ether: -O-

• Thiols: -SH

• Alkene: C=C

• Alkyne: C≡C

Example: Ethanol (alcohol), acetone (ketone), ethene (alkene).

Naming Alkanes, Alkenes, and Alkynes

Hydrocarbons are named based on the type of bonding and the length of the carbon chain.

• Alkanes: Saturated hydrocarbons; names end in -ane.

• Alkenes: Contain at least one double bond; names end in -ene.

• Alkynes: Contain at least one triple bond; names end in -yne.

• Number the chain to give the double or triple bond the lowest possible number.

Example: Butane (alkane), 2-butene (alkene), 1-butyne (alkyne).

Summary Table: Functional Groups and Their Properties

Functional Group	Structure	Key Properties	Example
Alcohol	-OH	Hydrogen bonding, higher boiling point	Ethanol
Phenol	Ar-OH	Acidic, antiseptic	Phenol
Ether	R-O-R'	Low boiling point, inert	Diethyl ether
Thiols	-SH	Strong odor, less hydrogen bonding	Ethanethiol
Aldehyde	-CHO	Reactive, can be oxidized	Formaldehyde
Ketone	-CO-	Dipole-dipole forces, solvent	Acetone
Alkene	C=C	Unsaturated, addition reactions	Ethene
Alkyne	C≡C	Unsaturated, addition reactions	Ethylene

Additional info: Academic context was added to expand brief points into full explanations, including examples, equations, and a summary table for clarity.