OCR A Level Chemistry: Amines Flashcards | Quizlet

What are amines?

Compounds derived from ammonia where one of the hydrogen atoms has been replaced with a carbon chain or ring.

What is a primary amine?

An amine where one alkyl or aryl group is attached to the nitrogen atom.

What is a secondary amine?

An amine where two alkyl or aryl groups are attached to the nitrogen atom.

What is a tertiary amine?

An amine where three alkyl or aryl groups are attached to the nitrogen atom.

What are the rules for naming a primary amine?

1. Identify the longest hydrocarbon chain and add the suffix amine. 2. If the amine group is not on carbon 1, the prefix amino is used instead, including the number to indicate the position of the amine group.

What are the rules for naming a secondary amine?

1. Identify the longest hydrocarbon chain attached to the nitrogen atom and add the suffix amine. 2. Identify the other smaller hydrocarbon chain and put it before the stem name. 3. Use the prefix N to show that the smaller group is attached to the nitrogen atom.

What are the rules for naming a tertiary amine?

1. Identify the longest hydrocarbon chain attached to the nitrogen atom and add the suffix amine. 2. Identify the other smaller hydrocarbon groups and put them before the stem name in alphabetical order. 3. The prefix N,N is added to show the smaller groups are attached to the nitrogen atom.

Why can amines act as bases?

The lone pair on the nitrogen atom can accept a proton.

What type of bond is formed when the lone pair on the nitrogen atom accepts a proton or donates to $BF_3$?

A dative covalent bond, because one atom (the nitrogen atom) supplies both shared electrons to the covalent bond.

What are examples of inorganic acids that react with amines to form salts?

Hydrochloric acid, Nitric acid, and Sulfuric acid.

What is the name of the mechanism for the synthesis of aliphatic amines from haloalkanes?

Nucleophilic substitution.

What occurs in Step 1 (salt formation) of the synthesis of a primary aliphatic amine?

Ammonia reacts with a haloalkane via nucleophilic substitution where ammonia acts as the nucleophile to attack the $\delta+$ carbon: $CH_3CH_2CH_2Cl + NH_3 \rightarrow CH_3CH_2CH_2NH_3Cl$.

What occurs in Step 2 (primary amine formation) of the synthesis of a primary aliphatic amine?

The ammonium salt reacts with a base to form a primary amine: $CH_3CH_2CH_2NH_3Cl + NH_3 \rightarrow CH_3CH_2CH_2NH_2 + NH_4Cl$.

Why must ethanol be used as the solvent instead of water in the synthesis of a primary amine?

Water cannot be used because it will turn the haloalkane into an alcohol via nucleophilic substitution; ethanol prevents substitution of the haloalkane by water.

Why is excess ammonia used in the formation of a primary amine?

It ensures all the haloalkane is used up and reduces/prevents further nucleophilic substitution of the amine group.

What reagents and conditions favour secondary amine, tertiary amine, or quaternary ammonium salt formation?

Heat, excess haloalkane, ethanol (solvent), and ammonia; this ensures further nucleophilic substitution of the haloalkane is possible.

What are the reagents, conditions, workup, and purification methods to prepare aromatic amines from nitroarenes?

Reducing agent is tin ($Sn$) and concentrated Hydrochloric acid under reflux at $100\text{c}$; sodium hydroxide is added to neutralise excess Hydrochloric acid; purified via solvent extraction and further distillation.

What is the equation for the preparation of an aromatic amine from nitrobenzene?

$$C_6H_5NO_2 + 6[H] \rightarrow C_6H_5NH_2 + 2H_2O$$

What are Steps 3 and 4 in the preparation of secondary aliphatic amines?

Step 3 (salt formation): $CH_3CH_2CH_2Cl + CH_3CH_2CH_2NH_2 \rightarrow (CH_3CH_2CH_2)_2NH_2Cl$. Step 4 (secondary amine formation): $(CH_3CH_2CH_2)_2NH_2Cl + NaOH \rightarrow (CH_3CH_2CH_2)_2NH + NaCl + H_2O$.

What are Steps 5 and 6 in the preparation of tertiary aliphatic amines?

Step 5 (salt formation): $CH_3CH_2CH_2Cl + (CH_3CH_2CH_2)_2NH \rightarrow (CH_3CH_2CH_2)_3NHCl$. Step 6 (tertiary amine formation): $(CH_3CH_2CH_2)_3NHCl + NaOH \rightarrow (CH_3CH_2CH_2)_3N + NaCl + H_2O$.

What is Step 7 in the preparation of quaternary ammonium salts?

Step 7 (salt formation): $CH_3CH_2CH_2Cl + (CH_3CH_2CH_2)_3N \rightarrow (CH_3CH_2CH_2)_4NCl$.

Why is a quaternary ammonium salt the final product in the successive nucleophilic substitution of amines?

There are no more protons left on the nitrogen atom in the quaternary ammonium salt for a base to deprotonate it.