Answer the following question:
(i) What is meant by the chirality of a compound? Give an example.
(ii) Which one of the following compounds is more easily hydrolyzed by KOH and why?
CH3CHCICH2CH3 or CH3CH2CH2Cl
(iii) Which one undergoes S N 2 substitution reaction faster and why?
(i)Chirality: It is a geometrical property of a rigid object ( or molecules ) by which it gets such spatial arrangement of points or atoms that, the molecule becomes non-super imposable of its mirror image.
The chiral molecule of the object does not have any element of symmetry like, a mirror image, centre of inversion (i) etc.
3-bromopent-1-ene is represented as
The centre of chirality is designated as *. It is due to the presence of four different groups.
(ii) Due to +I effect of alkyl groups the 2° carbonium ion CH3—CH+ —CH2—CH3 derived from sec. butyl chloride is more stable than the 1° carbonium ion CH3—CH2—C H2+ derived from n-propyl chloride. Therefore sec. butyl chloride gets hydrolyzed more easily than n-propyl chloride under SN1 conditions.
(iii)
Write the structure of an isomer of compound C4H9Br which is most reactive towards SN1 reaction.
Given reasons:
(i)C–Cl bond length in chlorobenzene is shorter than C–Cl bond length in CH3–Cl.
(ii)The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.
(iii)SN1 reactions are accompanied by racemization in optically active alkyl halides.
Give reasons for the following:
(i) Ethyl iodide undergoes SN2 reaction faster than ethyl bromide.
(ii) (±) 2-Butanol is optically inactive.
(iii) C -X bond length in halo benzene is smaller than C -X bond length in CH3- X.
Give reasons for the following:
(i) Phenol is more acidic than ethanol.
(ii) The boiling point of ethanol is higher in comparison to methoxymethane.
(iii) (CH3)3C - O - CH3 on reaction with HI gives CH3OH and (CH3)3C -I as the main products and not (CH3)3C -OH and CH3I.
