3 Marks Question

Question 13 Marks

Give reasons :
(i) Carbon-oxygen bond length in phenol is slightly less than that of methanol.
(ii) The $C - O - C$ bond angle present in ether is greater than the tetrahedral angle.
(iii) The boiling point of isomeric alcohols decreases with increase in branching.

Answer

(i) This is due to partial double bond character on account of oxygen of - OH (phenol) resonants with the benzene ring ( + M effect).
(ii) The reason for the $C - O - C$ bond angle present in ether is greater than the tetrahedral angle is the presence of ethyl group which have repulsion between them due to their large size. Along with this there is also a repulsion between the lone electron pairs present on oxygen.
(iii) This is because with increase in branching, Van der Waals forces of attraction decreases with decrease in surface area, hence boiling point decreases.

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Question 23 Marks

Give the equations of reaction of phenol with the following compounds:
(i) Benzene diazonium chloride
(ii) Acetone
(iii) Phthalic anhydride.

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Question 33 Marks

Explain the following reaction of $C _2 H _5 OH$ :
(a) Schotten Baumann reaction
(b) Reaction with concen. $HNO _3$
(c) Reaction with excess of $NH _3$
(d) Reduction with Red P and HI

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Question 43 Marks

An organic compound gives hydrogen on reacting with sodium metal. It also gives iodofom test and the end product of its oxidation is ethanoic acid. Name the compound and give the equation of these reactions.

Answer

According to question the comound gives iodo- form test, hence it must be alcohol or carbonyl compound but carboxyl compound does not react with sodium metal and the end product of oxidation of this compound is ethanoic acid, hence this compound will be ethanol. The equation of the reactions are as follows:

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Question 53 Marks

A compound $(X)$ reacts with $PCl_5$ to form compound $Y.$ Compound $Y$ reacts with ethereal solution of magnesium to form compound $(Z),$ which on treating with propanone and further hydrolysis to give $2-$Methyl propan$-2-ol. $ What are the compounds $X$ and $Y$ and also give the equations of the reactions.

Answer

The final product is $3^\circ$ alcohol of four carbon, which is obtained by reacting compound $Z$ with propanone. Therefore compound $Z$ is a carbon containing Grignard reagent, hence the starting compound will be a alcohol having one carbon. The reaction sequence will be as follows: