Advertisements
Advertisements
Question
Give plausible explanation for the following:
Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.
Advertisements
Solution
Due to the presence of three methyl groups at α-places, nucleophilic attack of CN– ions does not occur. This steric hindrance is absent in cyclohexane. Hence, nucleophilic attack of CN– ions occurs quickly. Hence, cyclohexanone cyanohydrin is obtained in good yield.
APPEARS IN
RELATED QUESTIONS
Acetaldehyde, when treated with which among the following reagents does NOT undergo addition reaction?
(A) Ammonia
(B) Hydroxylamine
(C) Ammoniacal silver nitrate
(D) Semicarbazide
Arrange the following in the increasing order of their reactivity towards nucleophilic addition reaction:
C6H5COCH3, CH3-CHO, CH3COCH3
Draw the structure of the semicarbazone of ethanal.
How will you bring about the following conversion in not more than two steps?
Bromobenzene to 1-Phenylethanol
Complete the synthesis by giving missing starting material, reagent or product.
How are the following compounds prepared?
acetophenone from benzene
Write balanced chemical equations for action of ammonia on - acetone
How will you convert benzoic acid to m-bromobenzoic acid?
What happens when propanone is treated with CH3MgBr and then hydrolysed?
Which of the following is most reactive in nucleophilic addition reactions?
The following questions are case-based questions. Read the passage carefully and answer the questions that follow:
| The carbon-oxygen double bond is polarised in aldehydes and ketones due to higher electronegativity of oxygen relative to carbon. Therefore, they undergo nucleophilic addition reactions with a number of nucleophiles such as HCN, NaHSO3, alcohols, ammonia derivatives and Grignard reagents. Aldehydes are easily oxidised by mild oxidising agents as compared to ketones. The carbonyl group of carboxylic acid does not give reactions of aldehydes and ketones. Carboxylic acids are considerably more acidic than alcohols and most of simple phenols. |
Answer the following:
(a) Write the name of the product when an aldehyde reacts with excess alcohol in the presence of dry HCl. (1)
(b) Why carboxylic acid is a stronger acid than phenol? (1)
(c) (i) Arrange the following compounds in increasing order of their reactivity towards CH3MgBr: (1)
CH3CHO, \[\begin{array}{cc}
\ce{(CH3)3C-C-CH3}\\
\phantom{....}||\\
\phantom{....}\ce{O}
\end{array}\], \[\begin{array}{cc}
\ce{CH3-C-CH3}\\
||\\
\ce{O}
\end{array}\]
(ii) Write a chemical test to distinguish between propanal and propanone. (1)
OR
(c) Write the main product in the following: (2)
| (i) |  |
| (ii) |  |
Draw structure of the following derivative.
Acetaldehydedimethylacetal
Why dissociation of HCN is suppressed by the addition of HCL?
Draw structure of the following derivative.
The ethylene ketal of hexan-3-one
The product of the following reaction is
\[\begin{array}{cc}
\ce{O}\phantom{.........}\\
||\phantom{.........}\\
\ce{C2H5 - C - CH3 ->[H2/Ni][\Delta] \phantom{..}?}\end{array}\]
Draw structure of the following derivative.
The ethylene ketal of hexan-3-one
Draw the structure of the given derivative.
The ethylene ketal of hexan-3-one
Give an example of the reaction in the following case.
Imine
Which of the following will not be formed when calcium formate is distilled with calcium acetate?
