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प्रश्न
What is meant by the following term? Give an example of the reaction in the following case.
2, 4-DNP-derivative
उत्तर
When an aldehyde or ketone reacts with 2, 4-dinitrophenylhydrazine in a weak acidic medium, 2, 4-dinitrophenylhydrazone (2, 4-DNP derivative) is produced.
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संबंधित प्रश्न
Predict the products of the following reactions:
Draw the structure of the semicarbazone of ethanal.
Arrange the following compound in increasing order of its reactivity in nucleophilic addition reactions.
Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone.
Hint: Consider steric effect and electronic effect.
Predict the product of the following reaction:
Predict the product of the following reaction:
\[\begin{array}{cc}
\phantom{..............}\ce{O}\\
\phantom{..............}||\\
\ce{R - CH = CH - CHO + NH2 - C - NH - NH2 ->[H+]}\end{array}\]
Predict the products formed when cyclohexanecarbaldehyde reacts with the following reagents.
Semicarbazide and weak acid
Write balanced chemical equations for action of ammonia on - acetaldehyde
Write the main product formed when propanal reacts with the following reagents:
H2N- NH2 followed by heating with KOH in ethylene glycol.
Alkenes 
and carbonyl compounds 
, both contain a π bond but alkenes show electrophilic addition reactions whereas carbonyl compounds show nucleophilic addition reactions. Explain.
The most stable reagent for the conversion of R – CH2OH → RCHO is
Arrange the following in the increasing order of their property indicated:
Ethanal, Propanone, Propanal, Butanone (reactivity towards nucleophilic addition)
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 structure of the following derivative.
Acetaldehydedimethylacetal
Draw the structure of the following derivative.
The ethylene ketal of hexan-3-one
Draw structure of the following derivative.
The ethylene ketal of hexan-3-one
Draw the structure of the following derivative.
Acetaldehydedimethylacetal
Draw structure of the following derivative.
The ethylene ketal of hexan-3-one
Draw structure of the following derivative.
The ethylene ketal of hexan-3-one
