Chemistry Class-11: Chapter –12. The Organic Chemistry Some Basic Principles and Techniques Part – 6

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Question: 37

The structure of triphenylmethyl cation is given below. This is very stable and some of its salts can be stored for months. Explain the cause of high stability of this cation.

The structure of triphenylmethyl cation

Stability

The structure of triphenylmethyl cation

Answer:

Stabilised due to nine possible canonical structures

Stabilised due to nine possible canonical structures

Canonial Structures

Stabilised due to nine possible canonical structures

Question: 38

Write structures of various carbocations that can be obtained from 2-methylbutane. Arrange these carbocations in order of increasing stability

Answer:

Four possible carbocations are

Order of increasing stability I < IV < II < III

Question: 39

Three students, Manish, Ramesh and Rajni were determining the extra elements present in an organic compound given by their teacher. They prepared the Lassaigne’s extract (L.E.) independently by the fusion of the compound with sodium metal. Then they added solid and dilute sulphuric acid to a part of Lassaigne’s extract. Manish and Rajni obtained prussian blue colour but Ramesh got red colour. Ramesh repeated the test with the same Lassaigne’s extract, but again got red colour only. They were surprised and went to their teacher and told him about their observation. Teacher asked them to think over the reason for this. Can you help them by giving the reason for this observation? Also, write the chemical equations to explain the formation of compounds of different colours.

Answer:

In Lassaigne’s test are formed due to the presence of sulphur and nitrogen both. These give red colour with . This happens when fusion is not carried out in the excess of sodium. With excess of sodium the thiocyanate ion, if formed, is decomposed as follows:

Question: 40

Name the compounds whose line formulae are given below:

(I)

Name the compounds whose line formulae

IUPAC Name

Name the compounds whose line formulae

(II)

Name the compounds whose line formulae

IUPAC Name

Name the compounds whose line formulae

Answer:

(i) 3-Ethyl-4-methylheptan-5-en-2-one

(ii) 3-Nitrocyclohex-1-ene.

Question: 41

Write structural formulae for compounds named as-

(a) 1-Bromoheptane

(b) 5-Bromoheptanoic acid

Answer:

(a)

(b)

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