amines and amides

Question 1

what is the composition of amines and amides?

Answer 1

ammonia molecule where an H is substituted with one or more alkyl groups

Question 2

properties of amines

Answer 2

• can be primary/secondary/tertiary
• nomenclature:
  
  • low property
• primary/secondary can form intermolecular H bonds
• tertiary amines can only form H bonds with molecules that have H bond donors
  
  • N is not as electronegative as O, so H bonds in amines are weaker than the H bonds in alcohols
• polar N-H bonds so can form H bonds in water
• longer change -> lower solubility

Question 3

describe the basic properties of ammonia

Answer 3

accepts H+

• basicity is influenced by alkyl groups
• alkyl chains have stabilising effect on + charge of protonated N
• alkyl chains hinder the binding of proton

Question 4

describe the nucleophilic properties of amines

Answer 4

amines have lone pair on electronegative N atom and can act as nucleophile to attack polarised bonds
- more nucleophilic than corresponding alcohol

Question 5

amine neutralisation

Answer 5

amine + acid -> salt formation (ammonium salt)

Question 6

quaternary ammonium compounds

Answer 6

have constant stable + charge on N (not bonded to H but to C compound)
- bonds cannot be dissociated easily (more stable)

Question 7

heterocyclic amine and examples

Answer 7

contain both carbon and non-carbon atoms in ring structures

• pyrrolidine
• pyrrole
• imidazole

Question 8

describe the condensation reaction of amines

Answer 8

acid + amine -> water + amides

Question 9

admiration/condensation of amides

Answer 9

carboxylic acid reacts with ammonia or primary/secondary amine (a lot of heat)

• amine reacts first with carboxylic acid-> depronoates it reducing amine nuclephilicity and carboxyl polarisation
• amide production through this reaction is accompanied by water release
• disfavours in aqueous solution
• this doesn’t happen to a significant degree (formation of ammonium salt is preferred)

Question 10

preparation of amides

Answer 10

anhydride or acid halogen as acyl donor

• both carry leaving group and don’t release water
  ex. in cells tRNA is used with peptide to form a amide bond

Question 11

nomenclature amides

Answer 11

adding -amide suffix

- alkyl groups prefix N followed by the alkyl name

Question 12

properties of amides

Answer 12

• resonance forms of amides lower the N basicity
• amide hydrolysis is thermodynamically favoured but kinetically disfavoured and neutral pH
• stability is water of amides makes them useful in biological environment
• in proteins an individual amino acid component is held together by amide bonds

Question 13

acid hydrolysis of amides

Answer 13

amide + water + acid -> carboxylic acid and ammonium salt

Question 14

base hydrolysis of amides

Answer 14

amide + water + base -> carboxylate salt and amine

-biologically catalysed by enzymes

Question 15

how are imines synthesised?

Answer 15

condensation of aldehydes or ketones with amines

• Nucleophilic addition followed by elimination of water
• Can be hydrolyzed back to the respective keto compounds and amines

Question 16

properties of imines

Answer 16

• primary imines: N-H bond
• secondary imines: H-hydrocarbon bond (schiff bases)
• contain C-N triple bond
• mildly basic