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प्रश्न
Acetone, Acetaldehyde, Benzaldehyde, Acetophenone – reactivity towards addition of HCN.
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उत्तर
Acetone, acetaldehyde, benzaldehyde, acetophenone - Reactivity with HCN
\[\begin{array}{c}\ce{CH3-C-CH3}\\\ce{||}\\\ce{O}\end{array}
\begin{array}{c}\ce{CH3-CHO}\\\ce{||}\\\ce{O}\end{array}\ce{C6H5CHO}\begin{array}{c}\ce{CH3-C-C6H5}\\\ce{||}\\\ce{O}\end{array}\]
Nucelophile addition by HCN is strongest for aldehyde than ketones. Also, acetophenone is more sterically hindered than acetone, hence comparatively less nucleophilic similarly C6 H5CHO i -s less reactive towards nucleophilic addition than CH3CHO.
\[\begin{array}{c}\ce{CH3-C-C6H5}\\\ce{||}\\\ce{O}\end{array}
\begin{array}{c}\ce{< CH3-C -CH3}\\\ce{||}\\\ce{O}\end{array}\ce{<C6H5CHO < CH3CHO}\]
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संबंधित प्रश्न
Draw the structure of the semicarbazone of ethanal.
What is meant by the following term? Give an example of the reaction in the following case.
Imine
Predict the products formed when cyclohexanecarbaldehyde reacts with the following reagents.
PhMgBr and then H3O+
Give plausible explanation for the following:
Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.
How are the following compounds prepared?
benzaldehyde from benzoyl chloride
Paraldehyde is formed as a result of polymerisation:-
What is the action of sodium hypoiodite on acetone?
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) |  |
Write the structure of the product formed when acetone reacts with 2, 4 DNP reagent.
Draw structure of the following derivative.
The ethylene ketal of hexan-3-one
