Introduction to Selected Homologous Series

Practice questions covering homologous series properties, systematic naming conventions, functional group structures, and comparative physical properties of organic compounds.

What are the four main characteristics of compounds in a homologous series?

(a) Same general formula, (b) same functional group and similar chemical properties, (c) gradual change in physical properties (like boiling point), and (d) adjacent members differ by a $-CH_2-$ unit.

How is a 'functional group' defined?

An atom or group of atoms responsible for most of the chemical properties of the compound.

What is the general formula for alcohols?

$$ROH$$

What is the general formula for aldehydes?

$$(H \text{ or } R)CHO$$

How can ketones be distinguished from aldehydes based on the position of the carbonyl group?

Aldehydes have the carbonyl group at the terminal position of the chain ($RCHO$), while ketones have the carbonyl group in a non-terminal position ($RCOR'$).

What is the systematic name for alcohols where the hydroxyl group ($-OH$) is directly attached to a benzene ring?

$$\text{Phenol}$$

What is the systematic name for an acid containing two carboxyl groups ($-COOH$)?

A dibasic acid, which uses the suffix $\text{-dioic acid}$.

Provide the trivial names for Trichloromethane, Propanone, and Ethanoic acid.

Trichloromethane: $\text{chloroform}$; Propanone: $\text{acetone}$; Ethanoic acid: $\text{acetic acid}$.

Explain why branched-chain alkanes have lower boiling points than straight-chain alkanes of similar relative molecular mass.

Branched-chain alkanes have a smaller surface area, which leads to weaker intermolecular forces.

Why are haloalkanes generally insoluble in water despite the polar carbon-halogen bond?

The hydrogen bonds between water molecules are much stronger than the van der Waals forces between haloalkane molecules; the energy required to break water's hydrogen bonds is greater than the energy released when forming new forces between haloalkane and water.

Why do alcohols have much higher boiling points than alkanes of similar relative molecular masses?

Due to the presence of strong hydrogen bonding between alcohol molecules.

What happens to the solubility of alcohols in water as the length of the hydrocarbon chain increases?

Solubility decreases because the non-polar alkyl group (which resembles an alkane) becomes larger, and van der Waals forces begin to predominate.

What structural feature allows carboxylic acids to have higher boiling points than alcohols with the same number of carbon atoms?

The carboxyl group ($-COOH$) can form more extensive hydrogen bonds, including the formation of stable $\text{dimers}$, which increases the effective molecular size and van der Waals forces.

Define 'esterification'.

The process of forming an ester by reacting an alcohol with a carboxylic acid.

Why do esters have lower boiling points than alcohols and carboxylic acids of similar molecular masses?

Esters lack a hydrogen atom attached to an oxygen atom, meaning they cannot form hydrogen bonds with each other.

Describe the hydrogen bonding capability of unsubstituted amides.

They have high boiling points because each hydrogen atom in the $-NH_2$ group can form a hydrogen bond with a lone pair on the oxygen atom of another molecule.

Why is the strength of hydrogen bonding in primary amines weaker than in alcohol molecules?

The electronegativity of nitrogen (N) is lower than that of oxygen (O), resulting in weaker hydrogen bonds.

What are the functional group and general formula for unsubstituted amides?

The functional group is the amide group ($-CONH_2$), and the general formula is $RCONH_2$.

According to the transcript, what rule is used to predict the major products of reactions between alkenes and hydrogen halides?

$$\text{Markovnikov's rule}$$

What are the characteristic smells of gaseous and liquid primary amines?

Gaseous amines have a characteristic ammonia smell, while liquid amines have a distinctive fishy smell.