Question
Read the passage given below and answer the following questions:
When an aldehyde with no et-hydrogen reacts with concentrated aqueous $NaOH$, half the aldehyde is converted to carboxylic acid salt and other half is converted to an alcohol. In other words, half of the reactant is oxidized and other half is reduced. This reaction is known as Cannizzaro reaction.

The following questions are multiple choice questions. Choose the most appropriate answer:
  1. A mixture of benzaldehyde and formaldehyde on heating with aqueous $NaOH$ solution gives:
  1. Benzyl alcohol and sodium formate.
  2. Sodium benzoate and methyl alcohol.
  3. Sodium benzoate and sodium formate.
  4. Benzyl alcohol and methyl alcohol.
  1. Which of the following compounds will undergo Cannizzaro reaction?
  1. $CH_3CHO$
  2. $CH_3COCH_3$
  3. $C_6H_5CHO$
  4. $C_6H_5CH_2CHO$
  1. Trichloroacetaldehyde is subjected to Cannizzaro's reaction by using NaOH. The mixture of the products contains sodium trichloroacetate ion and another compound. The other compounds is:
  1. 2, 2, 2-trichloroethanol.
  2. Trichloromethanol.
  3. 2, 2, 2-trichloropropanol.
  4. Chloroform.
  1. In Cannizzaro reaction given below:
$2\text{PhCHO}\xrightarrow{\stackrel{-}{\hbox{ OH}}}\text{PhCH}_2+\text{OH}+\text{PhCO}_2^-$ the slowest step is:
  1. The attack $^-OH$ at the carboxyl group.
  2. The transfer of hydride to the carbonyl group.
  3. The abstraction of proton from the carboxylic group.
  4. The deprotonation of $PhCH_2OH$.
  1. Which of the following reaction will not result in the formation of carbon-carbon bonds?
  1. Cannizzaro reaction.
  2. Wurtz reaction.
  3. Reimer-Tiemann reaction.
  4. Friedel-Crafts' acylation.

Answer

  1. (a) Benzyl alcohol and sodium formate.
Explanation:
It is an example of cross Cannizzaro reaction where aromatic aldehyde gets reduced to alcohol and aliphatic aldehyde gets oxidised to its sodium salt (both aldehydes must not contain any $\propto-$hydrogen).
  1. (c) $C_6H_5CHO$
  2. (a) 2, 2, 2-trichloroethanol.
Explanation:

The Cannizzaro product of given reaction yields 2, 2, 2-trichloroethanol.
  1. (b) The transfer of hydride to the carbonyl group.
​​​​​​​Explanation:
Hydride transfer is the slowest step.
  1. (a) Cannizzaro reaction.
​​​​​​​​​​​​​​​​​​​​​​​​​​​​Explanation:
C-C bond is not formed in Cannizzaro reaction while other reactions result in the formation of C-C bond.

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  3. $4f^0, 4f^2, 4f^{11}$
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  2. $CH_3CH_2OH$
  3. $C_6H_5CHO$
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  2. $CH_3CH_2CHO$
  3. $CH_3COCH_3$
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  1. $8, 6$
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  1. $6$
  2. $4$
  3. $8$
  4. $12$
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