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OCR A-level Chemistry > Chapter 27 - Amines, amino acids and polymers > Flashcards

Chapter 27 - Amines, amino acids and polymers Flashcards

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1
Q

What are amines?

A

Organic compounds in which one or more hydrogen atoms in ammonia (NH3) have been replaced by a carbon chain or ring

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2
Q

What is a primary amine?

A

Amine where the nitrogen atom is only bonded to one alkyl/aryl group, and 2 hydrogens

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3
Q

How do you name primary amines?

A

If NH2 is at the end of the chain: add suffix -amine to the name of the alkyl chain e.g. ethylamine

If the NH2 group is only any other carbon but carbon-1: use prefix amino- and number used to indicate position of the amine group along that chain e.g. 2-aminobutane

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4
Q

What is a secondary amine?

A

Amine where nitrogen atom is attached to 2 akyl/aryl groups and 1 hydogen

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5
Q

How do you name a seondary amine?

A

When amine has 2 of the same alkyl groups: prefixes di- used to indicate the number of alkyl groups attached to the notrogen atom. e.g. (CH3)2NH is dimethylamine

When 2 different alkyl groups attached to the nitrogen: the compound is named as a N-substituted derivative of the larger group. e.g. CH3NHCH2CH2CH3 is N-methylpropylamine

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6
Q

What is a tertiary amine?

A

Amine where the nitrogen atom is attached to 3 alkyl groups

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7
Q

How do you name tertiary amines?

A

If it has the same alkyl group: use prefix tri-

If it has 2 or more different alkyl groups attached to the nitrogen atom: the compound is named as a N-substituted derivative of the larger group e.g. CH3N(CH2CH3)CH2CH2CH3 is N-ethyl-N-methylpropylamine

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8
Q

What do amines often behave as?

A

Bases

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9
Q

How do amines behave as bases?

A

Lone pair of electrons on the nitrogen atom can accept a proton/H+.

When an amine accepts a proton, a dative covalent bond is formed between the lone pair of electrons on the nitrogen and the proton/H+.

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10
Q

What will a reaction between an amine and an acid make?

A

A salt (neutralisation reaction)

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11
Q

Write the equation for a reaction between propylamine and hydrochloric acid

A

CH3CH2CH2NH2 + HCl → CH3CH2CH2NH3+Cl-

forms salt - propylamonnium chloride

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12
Q

For the formation of primary amines, what is reacted together in the two steps?

A

salt formation:

Haloalkane and ammonia → ammonium salt

amine formation:

Salt and aqueous alkali (sodium hydroxide) → primary amine + ionic solid + water

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13
Q

In primary amine formation, what is in excess and why?

A
  • Ammonia in excess
  • Prevents further substitution of the amine group to form secondary and tertiary amines
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14
Q

In primary aliphatic amine formation, what is the purpose of ethanol?

A
  • solvent
  • prevents any substituion of the haloalkane by water to produce alcohols
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15
Q

What are the two steps of forming a secondary amine from a primary amine?

A

Primary amine + haloalkane and ethanol as solvent → ammonium salt

ammonium salt product + NaOH → secondary amine + ionic solid + water

  • tertiary amines formed by further reaction of the secondary amine
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16
Q

How is phenylamine (aromatic amine) made from nitrobenzene?

A

Nitrobenzene heated under reflux with tin and HCl to form ammonium salt (phenylammonium). Ammonium salt reacted with with excess NaOH to produce the aromatic amine, phenylamine

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17
Q

What do tin and HCl act as in formation of phenylamine from nitrobenzene?

A

Reducing agent

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18
Q

What is an amino acid?

A

Organic compound containing both amine (NH2) and carboxylic acid (COOH) functional groups

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19
Q

What is an alpha-amino acid?

A

Amino acids in which the amine group is attached to an alpha carbon (carbon next to the carboxyl group)

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20
Q

What is the general formula for an alpha amino acid?

A

RCH(NH2)COOH

where R is the side chain attached to the alpha carbon atom

21
Q

Amino acids are amphoteric, what does this mean?

A

Have acidic and basic properties

22
Q

How do amino acids react with acids to form ammonium salts?

A

Amine group is basic and reacts with acids to make salts

23
Q

What does an amino acid form when reacted with aqueous alkali such as sodium hydroxide?

A
  • Sodium salt and water

Carboxylic acid can react with alkalis

24
Q

How is an ester formed fro an amino acid?

A

Heating with an alcohol in the presence of concentrated sulphuric acid

(acidic conditions also pronate the basic amine group)

25
Q

What are amides?

A

Products of reactions of acyl chlorides with ammonia and amines.

CO- NH

26
Q

What are primary amides?

A

One carbon atom bonded to nitrogen atom

27
Q

What are secondary and tertiary amides?

A

secondary - 2 carbon atoms bonded to the nitrogen atom

tertiary - 3 carbons bonded to the nitrogen atom

28
Q

What is optical isomerism?

A
  • Type of steroisomerism
  • Compounds that are non-superimposible mirror images about a chiral centre
29
Q

What is a chiral centre?

A

carbon atom that is attached to 4 different atoms or group of atoms (in organic chemistry)

Any centre that holds attachments that can be arranged as two non-superimposible mirror images

30
Q

What is an enantiomers?

A

Pair of non-superimposible mirror image structures/ optical isomers

31
Q

What do optical isomers do?

A

Rotate plane-polarised light

32
Q

How do you draw optical isomers?

A

Drawn to show the 3D tetrahedral arrangement of the 4 different groups around the central chiral carbon atom. Other isomer is drawn as a mirror image, reflecting the first structure.

33
Q

How is a chiral carbon atom labelled?

A

with an asterisk

any carbon atom that is attached to 4 different groups/atoms

34
Q

What is condenstation polymerisation?

What is required for this?

A

Joining of monmers with loss of a small molecule, usually water (the condensation) or hydrogen chloride.

2 different functional groups

35
Q

What is a polyester?

A

Monomers joined together by ester linkages in a long chain to form a polymer

36
Q

How can a polyester be made from one monomer?

A

Monomer contains different functional groups - a hydroxyl (-OH) and a carboxyl group (-COOH)

Carboxylic acid group in one molecule reacts with alcohol group of another molecule

37
Q

How can a polyster be made from 2 monomers?

A
  • One monomer is a diol (with 2 hydroxyl groups) and one monomer is a dicarboxylic acid (with 2 carboxyl group) or diacyl chloride

a hydroxyl group on the diol reacts with a carboxyl group on the dicarboxylic acid/ diacyl chloride, forming an ester linkage and water/ hydrogen chloride

38
Q

What are some uses of polyesters?

A
  • Clothing
  • Plastics
  • electrical insulation
  • biodegradables
39
Q

What are polyamides?

A

Condensation polymers formed when monomers are joined together by amide linkages in a long chain to form a polymer.

40
Q

How can polyamides be formed from one monomer?

A

Amino acids contain both an amine group and a carboxylic acid group. Amino acids undergo condensation polymerisation to form a polypeptide/protein, which contains many different amino acids all linked together by amide bonds - losing water in the process.

41
Q

How can polyamides be formed from 2 monomers?

A

Reaction of a carboxylic acid (or acyl chloride) with a diamine

42
Q

What is required to undergo acid hydrolysis?

A

Excess hot aqueous HCl
H2O

43
Q

What is formed from polyester undergoing acid hydrolysis?

A
  • Diol
  • Dicarboxylic acid
44
Q

What is required to undergo base hydrolysis?

A

Excess hot aqueous NaOH

45
Q

What is formed from polyester undergoing base hydrolysis?

A
  • Diol
  • Salt of dicarboxylic acid
46
Q

What is formed from acid hydrolysis of polyamide?

A
  • Diammonium salt
  • Dicarboxylic acid
47
Q

What is formed from base hydrolysis of polyamide?

A
  • Diamine
  • Salt of dicarboxylic acid
48
Q

How does addition polymerisation differ from condensation polymerisation with monomers?

A

Addition - monomer contains C=C bond
Condensation - two monomers with two functional groups or one monomer with two different functional groups

49
Q

How does addition polymerisation differ from condensation polymerisation with backbone?

A

Addition - backbone of polymer is -C-C- bond
Condensation - polymer back bone contains ester or amide groups

OCR A-level Chemistry (30 decks)

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