amines, amino acids and polymers year 2

Question 1

what are amines

Answer 1

amines are the NH2 group. They are organic compounds, derived from ammonia, in which one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring

Question 2

aliphatic amines

Answer 2

nitrogen atom is attached to at least one straight or branched carbon chain (R group)
Methylamine is the simplest aliphatic amineCH3NH2

Question 3

aromatic amines

Answer 3

the nitrogen atom is attached to an aromatic ring (aryl group). Phenyl amine is the simplest
C6H2NH2

Question 4

classifying amines

Answer 4

amines are classified as primary, secondary or tertiary. This is decided by the number of alkyl or aryl groups attached to the nitrogen atom
eg primary NH2R
SECONDARY NHRR’
TERTIARY NRR’R’’

Question 5

naming amines

Answer 5

if amine group found on the end of the chain, add suffix amine to the name of the alkyl chain. eg butylamine
if amine group is found on any other carbon other than carbon 1 use amino prefix eg 2-aminobutane
- in secondary or tertiary amines, containing the same alkyl groups the prefixes di- or tri- are used to indicate the number of alkyl groups attached to the nitrogen atom eg (CH3)2NH is dimethylamine
- when 2 or more DIFFERENT groups are attached to a nitrogen atom the compound is named as a N-substituted derivative of the larger group eg CH3NHCH2CH2CH3 is N-methylpropylamine . The shorter alkyl group is added as the prefix
- if 3 different alkyl groups are attached to the nitrogen atom, two N prefixes will need to be applied for the 2 shortest alkyl groups and they will then be named alphabetically

Question 6

reasons for properties of amines

Answer 6

• properties of amines result from the lone pair on the nitrogen atom. Properties are similar to those of ammonia but are altered by the presence of alkyl groups
  -bonding around the nitrogen atom of an amine is similar to that of ammonia

Question 7

amines as bases

Answer 7

• lone pair is able to accept a proton (hydrogen ion)
  -dative covalent bond is formed between the lone pair of electrons on the nitrogen atom and the proton

Question 8

what 2 principles is base strength based on

Answer 8

• effect of substitute alkyl/ aryl groups. Alkyl groups release electrons towards the nitrogen atom. This is the inductive effect. Arylamines are significant weaker bases than alkylamines because of the involvement of the nitrogen lone pair in aromatic delocalisation
• solubility in water. Can form hydrogen bonds with water. Amines with small alkyl groups are soluble but amines with larger alkyl groups are less soluble in water. The large alkyl groups are unable to break the hydrogen bonds between the water molecules

Question 9

salt formation

Answer 9

• amines are bases and they neutralise acids to make salts eg propylamine reacts with HCl to form propylammonium chloride
  CH3CH2CH2NH2 +HCl –> CH3CH2CH2NH3+Cl-

Question 10

reaction of ethylamine with sulfuric acids

Answer 10

forms ethylammonium sulfate
2CH3CH2NH2 +H2S04 –> (CH3CH2NH3+)2 SO4 2-

Question 11

formation of primary amines

Answer 11

• ammonia has a lone pair of electrons on the nitrogen atom which allows ammonia to act as a nucleophile in substitution reaction with haloalkane. The product of this reaction is an ammonium salt. Aqueous alkali is then added to generate the amine from the salt
  salt formation :
  CH3CH2CH2Cl + NH3 –> CH3CH2CH2NH3+Cl-
  propylammonium chloride
  amine formation :
  CH3CH2CH2NH3+CL- +NaOH –> CH3CH2CH2NH2 + NaCl +H20

Question 12

essential conditions for formation of primary amines

Answer 12

• ethanol used as the solvent. Prevents any substitution of the haloalkane by water to produce alcohols
  -excess ammonia used . This reduces further substitution of the amine group to form secondary and tertiary amines
  THESE CONDITIONS LIMIT FUTHER SUBSTITUTION

Question 13

formation of secondary and tertiary amines

Answer 13

Reaction above is unsuitable for making a pure primary amine. Product still contains a lone pair of electrons on the nitrogen atom that can react further with a haloalkane to form a secondary amine. The product is again an ammonium salt
CH3CH2CH2Cl + CH3CH2Cl –>(CH3CH2CH2)2 NH2+ Cl-
The secondary amine is obtained from the salt by reacting the product with sodium hydroxide
(CH3CH2CH2)2 NH2+ Cl- + NaOH —> (CH3CH2CH2)2NH +NaCl + H20
tertiary amines can also be formed by further reaction of the secondary amine. In this example, further substitution would form tripropylamine (CH3CH2CH2)3N

Question 14

synthesis of aromatic amines

Answer 14

• nitrobenzene can be reduced by heating under reflux with a mixture of tin and conc HCl (acting as a reducing agent)
• then reacted with excess sodium hydroxide to produce the aromatic amine
• an ammonium salt is produced
  nitrobenzene + 6[H] —-> phenylamine + 2H20

Question 15

amino acids

Answer 15

• an organic compound containing both amine , NH2, and carboxylic acid, COOH, functional groups.
  -body has 20 common amino acids that can be built into proteins