Cyanohydrins
can be made from carbonyl compounds by generating
CN–
ions from HCN
in the presence of a weak base.
In a similar
reaction,
–CH2CO2CH3
ions are
generated from CH3CO2CH3
by
strong bases.
Which compound can be made from an aldehyde and
CH3CO2CH3
in
the presence of a strong base?
A
CH3CH(OH)CO2CH3
B
CH3CO2CH2CH(OH)CH3
C
CH3CH2CH(OH)CH2CO2CH3
D
(CH3)2C(OH)CH2CO2CH3
A and D are ruled out... as A does not use the correct reagent
while D is a ketone
B and C are close. Both B and C are aldehyde...B is ethanal and
in C it is propanal.
It's just the orientation otherwise both B and C seems
correct..
Please help.
Hi Hoay,
Yes, this is the classic Cambridge "ester group condensed
structural formula" trick question. C is the answer. B is wrong
because when the condensed structural formula of an ester is read
from left to right as R1COOR2, the same ester read from
right to left must be written as R2OCOR1 (and not R2COOR1).
Hence, B would be correct only if it is changed from
CH3COOCH2CH(OH)CH3 to CH3OCOCH2CH(OH)CH3.
Bonus related question (for A grade H2 Chem students) :
Draw the relevant resonance contributors and resonance hybrid of
the ester's conjugate base to explain why that particular proton is
the most acidic and is hence abstracted from the ester in the
presence of a non-nucleophilic and strong Bronsted-Lowry base, eg.
lithium diisopropylamide.