Answer the following:
(i) Haloalkanes easily dissolve in organic solvents, why?
(ii) What is known as a racemic mixture? Give an example.
(iii) Of the two Bromo derivatives, C6H5CH(CH3)Br and C6H5CH(C6H5)Br, which one is more reactive in Sn1 substitution reaction and why?
i) Haloalkanes can easily dissolve in organic solvents of low polarity because the new forces of attraction set up between haloalkanes and the solvent molecules are of same strength as the forces of attraction being broken.
(ii) A mixture of equal amounts of two enantiomers is known as racemic mixture. For example: When a 3° halide undergoes substitution with KOH, the reaction proceeds through SN 1 mechanism forming the racemic mixture in which one of the products has the same configuration as a reactant, while the other product has an inverted configuration.
(iii) In SN1 reaction mechanism leads through the carbocation pathway.
More stable the carbocation, more reactive will be substrate .the carbocation formed by two compounds are as follows:
Compound (C6H5)2CHBr = carbocation (C6H5)2CH+
Compound C6H5CH(CH3)Br=carbocation C6H5(CH3)CH+
Out of these two carbocations (C6H5)2CH+ is more stable than C6H5(CH3)CH+ because the carbocation(C6H5)2CH+ is resonance stabilised by two benzene rings .therefore (C6H5)2CHBr is more reactive than C6H5CH(CH3)Br. Resonance stabilisation of carbocation with one benzene ring is shown :
Although chlorine is an electron withdrawing group, yet it is ortho-, Para-directing in electrophilic aromatic substitution reactions. Explain why it is so?
Chlorobenzene is extremely less reactive towards a nucleophilic substitution reaction. Give two reasons for the same?
