InterviewSolution
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InterviewSolution
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(a)Indicate whether the following are S_(N^(1)),S_(N^(2)),E_(1) " or "E_(2) reactions. (i) CH_(3)CH_(2)CH_(2)CI+I^(-) to (ii) (CH_(3))_(3) CBr+CN^(-)(alc.) to (iii) CH_(3)CH(Br)CH_(3) +OH^(-) (alc.) to(iv) (CH_(3))_(3) C-Br+H_(2)O to (b) Give the decreasing order of reactivity of the alkaline hydrolysis of the following alkyl halides toward (A)S_(N^(1))(B) S_(N^(2))(C) in pressure of AgNO_(3). (i) (CH_(3))_(2)C(Br) -C_(2)H_(5) (ii)C_(5)H_(11)Br(iii) C_(2)H_(5)CH(Br)C_(2)H_(5) (c) Give the decreasing order reactivity of the alkaline hydrolysis of hte followinghalides towards S_(N^(1)) (i) MeCI (ii) PhCH_(2)CI(ii)Ph_(2)CHCI(iii)Ph_(3)C-CI. (d) Determine the relative S_(N^(2)) reactivity with NaCI in aprotic DMSO of the following alkyl halides : (A) (i) CH_(3)CHCICH_(2)CH_(3)(ii)CH_(3)CHBrCH_(2)CH_(3) (iii) CH_(3)CHICH_(2)CH_(3)(B) (i) CH_(3)CH(CH_(3))CH_(2)CH_(2)I(ii) CH_(3)CH(CH_(3))CHICH_(3)(iii) CH_(3)CI(CH_(3))CH_(2)CH_(3)(e) Arrange the following in the order of decreasing nucleophilic character: H_(2)O,^(-)OH,CH_(3)O^(-), CH_(3)COO^(-)(f) Arrange thefollowing in the decreasing order as leaving group in S_(N) reaction: CH_(3)COO^(-),C_(6)H_(5)O^(-), C_(6)H_(5)SO_(3)^(-), CH_(3)O^(-) |
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Answer» Solution :`(a) (i) CH_(3)CH_(2)CH_(2)-I " is" S_(N^(2)) " reaction "(1^(@)"halide and " I^(-)` is a good nucleophile and poor base. `(II) CH_(3)CH=CH_(2) " is " E_(2)` reaction, less polar SOLVENT favours `E_(2)`. `(iv) (CH_(3))_(3)C-OH " is "S_(N^(1))` reaction as `H_(2)O` is not basic enough to remove a proton to give ELIMINATION reaction. `(b) (A) (i) gt (iii) (3^(@) gt 2^(@) gt 1^(@)" alkyl halides ")S_(N^(1))`. `(B) (ii) gt (iii) gt (i) (1^(@) gt 2^(@) gt 3^(@) " alkyl halides")S_(N^(2)).` `(C) (i) gt (iii) gt (ii) : " Heavy ions such as " Ag^(+)" or " Pb^(2+) " catalyse " S_(N^(1))`. `(C) (iv) Ph_(3) C-CI gt (iii) Ph_(2) CH-CI gt (ii) PhCH_(2) -CI gt (i) NeCI.` `(d) (A) (iii) gt (ii) gt (i) ("Group leaving ability is " I^(-) gt Br^(-) gt CI^(-))` `(B) (i) gt (ii) gt (iii) ("steric factor MAKES the reactivity " 1^(@) gt2^(@) gt 3^(@))`. (e) When the NUCLEOPHILIC centre is same . The nucleophilicity is same as basic character. Acidic character :`H_(3)O^(+) gt CH_(3)COOHgt CH_(3)OH gt H_(2)O.` Basicity and nucleophilicity : `H_(2)O lt CH_(3)COO^(-) lt CH_(3)O^(-) lt OH^(-)`. (f) Weaker thebase or stronger the acid, better is the leaving group. Acidic character : `C_(6) H_(5)SO_(3)H gt CH_(3)COOH gt C_(6)H_(5)OH gt CH_(3) OH.` |
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