Q1.Lidocaine is a local anaesthetic used in dentistry and in minor surgical operations.
The synthesis of lidocaine in 2 steps from 2,6-dimethylphenylamine is shown.
 
(a)     (i)      Give the IUPAC name of reagent X in Step 1.
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(1)
(ii)     Outline a mechanism for Step 1.
In your answer, use RNH2 to represent 2,6-dimethylphenylamine.
(4)
(b)     Name the mechanism for Step 2.
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(1)
(c)     Which of these is the total number of peaks in the 13C n.m.r spectrum of lidocaine?
Tick (✔) one box.
 
 	8		9		11		12		

(1)

(d)     Calculate the percentage by mass of hydrogen in a molecule of lidocaine.
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(2)
(e)     Give the name, including the classification, of the functional group that contains the nitrogen atom labelled b.
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(1)
(f)      Lidocaine is used medically as the salt lidocaine hydrochloride.
(i)      Suggest which one of the nitrogen atoms labelled a or b is protonated in lidocaine hydrochloride. Explain your answer.
Nitrogen atom protonated .........................................................................
Explanation ...............................................................................................
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(3)
(ii)     Suggest why lidocaine hydrochloride is used medically in preference to lidocaine.
Explain your answer.
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(2)
(Total 15 marks)
Q2.          (a)     Name and outline a mechanism for the formation of butylamine, CH3CH2CH2CH2NH2, by the reaction of ammonia with 1-bromobutane, CH3CH2CH2CH2Br.
Name of mechanism ....................................................................................
Mechanism

 

 
(5)
(b)     Butylamine can also be prepared in a two-step synthesis starting from 1-bromopropane, CH3CH2CH2Br. Write an equation for each of the two steps in this synthesis.
Step 1
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Step 2
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(3)
(c)     (i)      Explain why butylamine is a stronger base than ammonia.
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(ii)     Identify a substance that could be added to aqueous butylamine to produce a basic buffer solution.
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(3)
(d)     Draw the structure of a tertiary amine which is an isomer of butylamine.

 
 
(1)
(Total 12 marks)

 

M1.(a)     (i)      (2-)chloroethan (-1-) oyl chloride
2 not required but penalise 1- or other numbers at start. Ignore 1 in ethanoyl
Ignore hyphens, commas, spaces
1
(ii)     
M1 for arrow from lp on N to C
(or to space half way between N and C)
If full amine drawn, ignore slips except in –NH2
M2 for arrow from C=O bond to O
Not score M2 as an independent first step, but can allow M1 for attack on C+ produced
If Cl lost at this stage, Max 1 for M1
M3 for structure of ion including 2 charges
M4 for 3 arrows and lp on O
- may be scored in two steps
Ignore use of RNH2 to remove H+ in M4, but penalise use of Cl-
4
(b)     Nucleophilic substitution
Allow minor spelling errors e.g. nucleophyllic
1
(c)     9
1

(d)     Mr = 234(.0)
9.4 scores 2 marks
1
% H = 9.4(0)
M2 = 
If Mr = 234 not shown, can score M1 if their answer × 234 = their no of H
1

(e)     Tertiary amine OR 3o amine OR IIIo amine
Ignore N- substituted
1

(f)     (i)      If a given: CE=0, can only score if answer given is b
M1 lp on Nb or on b
M2 alkyl groups donate electron density or positive inductive effect or electron donating groups attached
M3 (lp on Nb) more available or protonated amine stabilised or better lp donor/H+ acceptor
Ignore reference to nucleophiles
NOTE – there is NO mark for b alone
Alternatives
M1 lp on Na or on a
M2 lp or electrons (on Na) delocalised into ring /towards O in C=O
M3 (lp on Na) less available (to bond to H+/accept proton)
1
1
1

(ii)     Salt is ionic
Independent marks
1
(More) soluble (in blood/body fluids/water)
1
[15]

M2.          (a)     Nucleophilic substitution

1
          M1, M2 and M4 for arrows, M3 for structure of cation
(Allow M2 alone first, i.e. SN1 formation of carbocation)
(Penalise M4 if Br– used to remove H+)

4
(b)     Step 1        CH3CH2CH2CN   1
CH3CH2CH2Br + KCN → CH3CH2CH2CN + KBr balanced
1
                            (or CN–) (or Br–)
                   (not HCN)
1
Step 2        CH3CH2CH2CN + 2H2 → CH3CH2CH2CH2NH2
                     (or 4[H])
1

(c)     (i)      Lone pair (on N) (in correct context)
1
R group increases electron density / donates electrons /pushes
electrons / has positive inductive effect
1
(ii)     Any strong acid (but not concentrated)
or any amine salt or ammonium salt of a strong acid
1

(d)     CH3CH2N(CH3)2
1
[12]