Consider the following compounds:
(i) CH₃CH₂Br
(ii) CH₃CH₂CH₂Br
(iii) CH₃CH₂CH₂CH₂Br
Arrange the compounds in the increasing order of their boiling points.
(iii) < (ii) < (i)
Step 1: Understanding boiling points. Boiling points are affected by molecular size and the type of intermolecular forces. The more carbon atoms and longer the chain, the higher the boiling point.
Step 2: Analysis of the compounds.
- Compound (i) CH_3CH_2Br has a relatively small chain, resulting in a lower boiling point.
- Compound (ii) CH_3CH_2CH_2Br has a longer chain, leading to higher boiling point.
- Compound (iii) CH_3CH_2CH_2Br, with the largest size, has the highest boiling point.
Step 3: Conclusion. Thus, the correct order of boiling points is (i)<(ii)<(iii), corresponding to option (B).
Write IUPAC names of the following compounds and classify them into primary, secondary and tertiary amines.
(i) (CH3 )2CHNH2 (ii) CH3 (CH2 )2NH2 (iii) CH3NHCH(CH3 )2
(iv) (CH3 )3CNH2 (v) C6H5NHCH3 (vi) (CH3CH2 )2NCH3 (vii) m–BrC6H4NH2
Give one chemical test to distinguish between the following pairs of compounds.
(i) Methylamine and dimethylamine
(ii) Secondary and tertiary amines
(iii) Ethylamine and aniline
(iv) Aniline and benzylamine
(v) Aniline and N-methylaniline
Account for the following:
(i) pKb of aniline is more than that of methylamine.
(ii) Ethylamine is soluble in water whereas aniline is not.
(iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
(iv) Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.
(v) Aniline does not undergo Friedel-Crafts reaction.
(vi) Diazonium salts of aromatic amines are more stable than those of aliphatic amines. (vii) Gabriel phthalimide synthesis is preferred for synthesising primary amines.
Give Reasons:
(I) \( \text{Ce}^{4+} \) in aqueous solution is a good oxidising agent.
(II) The actinoid contraction is greater from element to element than lanthanoid contraction.
(III) \( E^\circ_{\text{M}^{2+}/\text{M}} \) value is more negative than expected, whereas \( E^\circ_{\text{Cu}^{2+}/\text{Cu}} \) is positive.