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प्रश्न
What is meant by the following term? Give an example of the reaction in the following case.
Cyanohydrin
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उत्तर
Aldehydes and ketones react with hydrogen cyanide (HCN) to yield cyanohydrins. This reaction occurs very slowly with pure HCN. Therefore, it is catalysed by a base and the generated cyanide ion (CN−) being a stronger nucleophile readily adds to carbonyl compounds to yield corresponding cyanohydrin.
\[\ce{HCN + O\overset{-}{H} <=> {_{\bullet}^{\bullet}}\overset{-}{C}N + H2O}\]
APPEARS IN
संबंधित प्रश्न
Draw the structure of the semicarbazone of ethanal.
Write the products formed when CH3CHO reacts with the following reagents : H2N – OH
Give plausible explanation for the following:
Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.
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What is the action of the following reagents on ethanoic acid?
1) `LiAlH_4"/"H_3O^+`
2) `PCl_3 , "heat"`
3) `P_2O_5, "heat"`
Write the main product formed when propanal reacts with the following reagents:
2 moles of 3 CH OH in presence of dry HCl
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Alkenes 
and carbonyl compounds 
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What happens when propanone is treated with CH3MgBr and then hydrolysed?
The increasing order of the following compounds towards HCN addition is:
| (i) |  |
| (ii) |  |
| (iii) |  |
| (iv) |  |
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\[\ce{Carbonyl compound + MeOH <=>[HCl] acetal}\]
Rate of the reaction is the highest for ______.
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 structures of the given derivatives.
The ethylene ketal of hexan-3-one
Draw structures of the given derivatives.
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Give an example of the reaction in the following case.
Oxime
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The major product of the following reaction is:
