Nitrogen Compounds (OCR A Level Chemistry A): Flashcards
Exam code: H432
1/280Still learning
Know0
- FrontAmines
Define amine
Was this flashcard helpful?
Cards in this collection (28)
Define amine
An amine is a derivative of ammonia in which one or more hydrogen atoms are replaced by an alkyl or aryl group.
Why can amines act as bases in aqueous solution?
The nitrogen atom has a lone pair of electrons that it can donate to a proton (H+), forming a dative bond and acting as a proton acceptor.
Amines are classified as primary, secondary or tertiary based on the number of hydrogens replaced on the .......... atom.
Amines are classified as primary, secondary or tertiary based on the number of hydrogens replaced on the nitrogen atom.
True or False?
A primary amine has one hydrogen atom remaining on the nitrogen.
True.
In a primary amine, one hydrogen of ammonia has been replaced by an alkyl or aryl group, leaving one N–H bond.
What is the difference between an aliphatic amine and an aromatic amine?
An aliphatic amine has an alkyl group (e.g. methyl, ethyl) attached to the nitrogen, while an aromatic amine has an aryl group such as a phenyl ring.
Ethylamine reacts with hydrochloric acid to form the salt .......... chloride.
Ethylamine reacts with hydrochloric acid to form the salt ethylammonium chloride.
Why do amine salts with longer alkyl chains become less soluble in water?
As the carbon chain increases in length, the non-polar character of the molecule increases, reducing interactions with polar water molecules.
Define nucleophilic substitution (in amine preparation)
A nucleophilic substitution is a reaction in which a nucleophile donates its lone pair to replace a leaving group; used to prepare amines from halogenoalkanes reacting with ammonia or primary amines.
What reagents and conditions are needed to prepare a primary amine from a halogenoalkane?
Excess, hot ethanolic ammonia is used under pressure; the nitrogen lone pair acts as a nucleophile and replaces the halogen in a nucleophilic substitution reaction.
Nitriles can be reduced to primary amines using .......... in dry ether or hydrogen gas with a .......... catalyst.
Nitriles can be reduced to primary amines using LiAlH4 in dry ether or hydrogen gas with a nickel catalyst.
True or False?
Reacting a halogenoalkane with a primary amine produces a secondary amine.
True.
The nitrogen lone pair of the primary amine acts as a nucleophile and replaces the halogen, giving a secondary amine in a nucleophilic substitution reaction.
Why is excess sodium hydroxide added in stage 2 of phenylamine preparation?
Excess NaOH(aq) is added to deprotonate the phenylammonium ions (C6H5NH3+) formed under the acidic conditions of stage 1, releasing phenylamine.
In stage 1 of phenylamine preparation, nitrobenzene is heated under reflux with tin and .......... acid, which act as .......... agents.
In stage 1 of phenylamine preparation, nitrobenzene is heated under reflux with tin and concentrated hydrochloric acid, which act as reducing agents.
Why does reducing a nitrile produce a primary amine rather than a secondary or tertiary amine?
The –CN group contains only one carbon bonded to nitrogen, so reduction converts it to –CH2NH2, which has no additional substituents on the nitrogen atom.
Define amino acid
An amino acid is an organic compound containing both a basic amino (–NH2) group and an acidic carboxylic acid (–COOH) group.
Why are amino acids described as amphoteric?
They contain both an acidic –COOH group and a basic –NH2 group, so they can act as both an acid and a base.
The general structural formula of a naturally occurring 2-aminocarboxylic acid is .........., where R is a variable side chain.
The general structural formula of a naturally occurring 2-aminocarboxylic acid is RCH(NH2)COOH, where R is a variable side chain.
What happens when an amino acid reacts with hydrochloric acid?
The amino group accepts a proton from HCl, forming a positively charged ammonium salt with a –NH3+ group.
True or False?
Amino acids can be esterified by heating with an alcohol in the presence of concentrated sulfuric acid.
True.
The carboxylic acid group undergoes esterification while the amino group is protonated under the acidic conditions.
What product forms when an amino acid reacts with sodium hydroxide solution?
The carboxylic acid group reacts with NaOH to form a sodium salt and water, while the amino group is unaffected.
True or False?
There are 20 naturally occurring amino acids, all with the amine group on the carbon adjacent to the carboxylic acid group.
True.
These are 2-aminocarboxylic acids, and they serve as the building blocks of proteins.
Define amide
An amide is a compound formed by the condensation reaction of a carboxylic acid or acyl chloride with ammonia or an amine, with the general structure RCONR2.
How is the classification of amides as primary, secondary or tertiary determined?
By the number of carbon atoms bonded to the amide nitrogen: one carbon (primary), two carbons (secondary), or three carbons (tertiary). One must always be the carbonyl carbon.
The IUPAC name of CH3CONH2 is .........., formed from a two-carbon chain with an amide group.
The IUPAC name of CH3CONH2 is ethanamide, formed from a two-carbon chain with an amide group.
True or False?
Amide bonds are found in proteins, linking amino acid residues together.
True.
The amine group of one amino acid reacts with the carboxylic acid group of another in a condensation reaction to form a peptide (amide) bond.
How is an alkyl group on the nitrogen named in a secondary amide?
The alkyl group is placed at the start of the name with the prefix N- to indicate it is bonded to the nitrogen, followed by the name of the carbonyl chain ending in -amide.
For a tertiary amide with two different alkyl groups on the nitrogen, the groups are listed in .......... order and the prefix .......... is used if both groups are identical.
For a tertiary amide with two different alkyl groups on the nitrogen, the groups are listed in alphabetical order and the prefix di- is used if both groups are identical.
Why are amides described as condensation products rather than addition products?
A small molecule (water or HCl) is eliminated during the reaction between the carboxylic acid or acyl chloride and the amine, which is the defining feature of a condensation reaction.
Sign up to unlock flashcards
or