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.
Originally posted by hoay:
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.
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.
dont you think that in the presence of strong base –CH2CO2CH3 ions will attack either ethanal to produce the compund in choice B. It does make sense that this will be formed...then why we treat it as ester.
Originally posted by hoay:dont you think that in the presence of strong base –CH2CO2CH3 ions will attack either ethanal to produce the compund in choice B. It does make sense that this will be formed...then why we treat it as ester.