6.2.2 Amino acids, amides and chirality

what groups do amino acids contain

amine group and carboxylic acid

α-amino acid

both groups are attached to the same carbon atom

general formula of α-amino acid

RCH(NH2)COOH

general strucure of α-amino acid

how to name amino acids systematically

1. Identify the longest carbon chain that includes the carboxyl carbon.

2. Start numbering the carbons from the carboxyl carbon, assigning it the number 1.

3. Specify the position and identity of the amine substituent.

why are amin acids bi functional

they have both carboxyl and amine groups so can act as an cid or base and react with an acid or base

reaction of amino acids with alkalis

The carboxyl group can react with aqueous alkalis such as NaOH_(aq) to form carboxylate salts and water.

reaction of amino acids with acids

The amine group can react with acids like HCl to form ammonium salts.

esterification of amino acids

The carboxyl group is capable of reacting with alcohols to form esters and water, in a reaction catalysed by concentrated H₂SO₄

functional group of amides

CONH₂

Primary amide

These are amides where the nitrogen atom is bonded to one carbonyl group (C=O) and two hydrogen atoms

secondary amide

These are amides where the nitrogen atom is bonded to one carbonyl group (C=O), one hydrogen atom and one alkyl or aryl group

tertiary amide

These are amides where the nitrogen atom is bonded to one carbonyl group (C=O), and two alkyl or aryl groups.

how to name primary amides

stem of the alkane followed by amide

how to name secondary amide

• look for the chain containing the carbonyl group and name as if were a primary amide

• add prefix to show the other alkyl group on nitrogen

• in fornt of everthign add N-

how can primary amides be formed

The reaction between acyl chlorides and ammonia produces primary amides

ehtanoyl chloride reaction with ammonia

ethanoyl chloride reacts with ammonia to give ethanamide and HCl:

CH₃COCl + NH₃ ➔ CH₃CONH₂ + HCl

how can seconary amides be formed

The reaction between acyl chlorides and primary amines produces secondary amides, also known as N-substituted amides.

ethanoyl chloride reaction with methylamine

thanoyl chloride reacts with methylamine to give N-methylethanamide and HCl:

CH₃COCl + CH₃NH₂ ➔ CH₃CONHCH₃ + HCl

optical isomerism

type of stereoisomerism where isomers have the same structural formula but different arrangements of atoms in space

chiral carbon

 chiral carbon is a carbon with four different groups attached to it.

when the groups around a chiral centre are arrnaged differently what does it result in

two non-superimposable mirror image structures.

what are the molecules called when the groups are arranged in 2 different ways around chiral carbon atoms

enantiomers or optical isomers

how to identify and draw optical isomers

1. Identify the chiral carbon - Carefully draw all hydrogen atoms to clearly identify each attachment. Look for the carbon atom connected to four different groups.

2. Sketch the optical isomers - Illustrate one isomer with its groups arranged tetrahedrally around the chiral carbon. Next, draw its mirror image.

what happens if a molecules has more than one chiral centres

have more than 2 optical isomers