Chapter 27: Amines, Amino Acids, and Proteins (27.1 - 27.3)

Question 1

Formula of ammonia

Answer 1

NH3

Question 2

What are amines

Answer 2

Amines are an organic compound formed when one or more hydrogen atoms in ammonia has been replaced by a carbon chain or ring

Question 3

What is an aliphatic amine

Answer 3

The nitrogen atom is bonded to at least one alkyl group (straight or branched carbon chain)
Simplest is methylamine, CH3NH2, with one methyl group attached to the nitrogen

Question 4

What is an aromatic amine

Answer 4

Nitrogen atom is attached to an aryl group (aromatic ring)

Simplest is phenylamine, C6H5NH2, with a phenyl group attactehd to the nitrogen atom

Question 5

How are amines classified

Answer 5

Primary: R-NH2. N at attached to 1 R group
Secondary: N attached to 2 R groups (and 1 H)
Tertiary: N attatched to 3 R groups

Question 6

How do you make a polyester from one monomer?

Answer 6

The monomer must contain both a hydroxyl and a carboxyl group

Carboxylic acid reacts with alcohol, forming an Ester linkage and water

Question 7

How are polyesters made from two monomers?

Answer 7

When one monomer is a diol and one is a carboxylic acid

A hydroxyl group reacts with the carboxyl group, forming an Ester link and water

Question 8

What two ways can you make a polyamide From one monomer?

Answer 8

With an amino acid which has an amine group and a carboxylic acid - forms a Peptide bond and water

Monomer with an amine group and an acyl chloride - forms an Peptide bond and hydrogen chloride

Question 9

Which two ways can you make a polyamide from two monomers?

Answer 9

Reacting a dicarboxylic acid with a diamine.

Reacting a diacyl chloride with a diamine

Question 10

Why are polyamides and polyesters strong?

Answer 10

They will have hydrogen bonds between chains and they have very strong London forces as they are long and have lots of points of contact

Question 11

How do you hydrolyse a polyester?

Answer 11

1) With hot aqueous alkali e.g NaOH and water - makes a dicarboxylate salt (COO-Na+) and a diol
2) With hot aqueous acid e.g HCl and water - makes a diol and a dicarboxylic avid

Question 12

How do you hydrolyse a polyamide?

Answer 12

NaOH and water - makes a diamine and a dicarboxylate salt (COO-Na+)

H+/H2O - makes a dicarboxylic acid and a compound with an NH3+ group on either end

Question 13

how do amines behave as bases

Answer 13

The lone pair of electors on the N atom accepts a proton

A dative covalent bond forms between the lone pain of the N atom and the H+

Question 14

amine + acid –>

Answer 14

amine + acid –> salt
amines neutralise dilute acids to form salts
eg CH3CH2NH2 + HCl –> CH3CH2NH3+Cl-

Question 15

aliphatic amines are prepared by:

Answer 15

1) substitution of haloalkanes with excess ethanoic ammonia to form a salt:
CH3CH2NH2 + NH3 –> CH3CH2NH3+Cl-

2) Excess ammonia substitutes the halide
CH3CH2NH3+CL- + NH3 —> CH3CH2NH2 +NH4CL

Question 16

the use of ethanol in the preparation of aliphatic amines

Answer 16

Ethanol is a solvent, used to prevent substitution of the haloalkane by water to produce alcohols

Question 17

Aromatic amines are prepared by:

Answer 17

1) reduction of nitroarenes by refluxing with tin and concentrated hydrochloric acid

Question 18

what is an amino acid?

Answer 18

an organic compound containing both amine (NH2) and carboxylic acid (COOH) functional groups.
Because they contain both an acidic COOH and a basic NH2 functional group, amino acids have similar reactions to both carboxylic acids and amines

Question 19

what is an α-amino acid? (alpha-amino)

Answer 19

an amino acid with the NH2 and COOH groups attached to the same α-carbon atom

NH2-CH(R)-COOH
[ normally written as RCH(NH2)COOH ]

Question 20

amino acid reaction with alkalis

Answer 20

COOH group reacts with aqueous alkali to form salt and water

H2N-CH2-COOH + NaOH –> H2N-CH2-C(O)O-Na+ + H2O

Question 21

esterification of amino acids

Answer 21

COOH group can be esterified by heating with an alcohol with a concentrated H2SO4 catalyst
The acidic conditions protanone the basic NH2 to form -NH3+
H2N-CH2-COOH + C2H5OH + H+ –> H3N+-CH2-COOC2H5 + H2O

Question 22

amino acids reaction with acids

Answer 22

NH2 groups neutralise an acid to form a salt.

eg reaction with HCl would change NH2 group to NH3+ and leave a Cl- ion

Question 23

how are amides classified

Answer 23

Primary: 1 carbon atom bonded to N
Secondary: 2 carbon atoms bonded to N
Tertiary: 3 carbon atoms bonded to N

Question 24

Two types of stereoisomers?

Answer 24

2 types: optical and E/Z

Question 25

optical isomerism

Answer 25

Found in molecules that contain a chiral centre

• a chiral carbon atom is attached to 4 different atoms or groups of atoms, often labelled with an asterisk * in diagrams
• optical isomers are when the 4 groups attached to the chiral carbon are arranged in space as two non-superimposable mirror images
• each chiral carbon atom in an organic molecule has one pair of optical isomers

Question 26

why do α-amino acids have optical isomers

Answer 26

all α-amino acids (except glycine H2NCH2COOH) contain a chiral carbon atom

Question 27

what is an amide?

Answer 27

R-CO-N(R’)-R’’

organic compounds that are derivatives of carboxylic acids

Question 28

hydrolysis of polyesters

Answer 28

• acid hydrolysis produces carboxylic acid + alcohol

- alkaline hydrolysis produces carboxylate salt + alcohol

Question 29

hydrolysis of polyamides

Answer 29

• acid hydrolysis produces carboxylic acid + ammonium salt

- alkaline hydrolysis produces carboxylate salt + an amine

Question 30

types of hydrolysis to break down a substance

Answer 30

• Acid hydrolysis: hot aqueous acid eg. HCl (aq)

- Alkaline hydrolysis: hot aqueous alkali eg. NaOH (aq)

Question 31

Why might a polymer not have the same Mr as expected?

Answer 31

It is likely that the polymer has 2 groups on it which can react together to form a ring

Question 32

If you want one optical isomer from a synthesis what method should you use?

Answer 32

1) use enzymes or bacteria

2) Chiral catalyst