Question

Which haloalkane shown below would be expected to react the fastest in a typical SN 1 reaction? CH 1-C-CH3 CH3 CH; Br-C-C=CH CI-C-CH; H CH; CH; (b) CH4Cl CH; (d) CH; I-d-c-CH₂ CH I-C -C=CH2 CH31 н H CH H (f)

Answer 1

Haloalkane ' e ' would be expected to react fastest in a typical S_N¹ reaction .

The detail explanation is shown below .

The resonance stabilized carbocarion is the most stable carbocation than the other types of carbocation .

R2 102-X A scheme for Nucleophilic substitution uni- -molecular reeaction (SN") is shown below RI R, R, -X Nu une ca nu R3 R₂ (fast) R2 R3 (x = leaving group) (stable carbo- (final -cation product). intermediate) speed of SN' reaction depends upon the nature of the wearing group and the stabi Carbo cation intermediate. ability of iodine is s higher than bromine larger size and orbital missmatch with central carbo atom of stability of the The leaving group due rodine. CH3 CH3 -Bye ta) Br -c-cz H ц G=CH₂ oc-c=CH2 =(-CH2 1 Catz CH₂ The carbocation stabilized by electrona sundonating inductive effect by two 3 group (+1 effect). also stabilized by hyper conjugative effect of six hydrogens. Carbo cation resonance stabilized. this is

CH3 + (b) el - A et cHz CHZ CH3 (learring group is chlorine) This combocation is stabilized by + reffert tion- of thore elig groups and hyper conjugation effect of nine hydrogens, CH3 I-c- ockchz CH₂ (stabilized by +1 effect of three chiz groups and nine hyper congu- gative hydrogens). carbocation ) stability, (d) - elize CH₂ No sto CH3 CH3 CH3 le) 1 - - (=CH2 @c-(=CH2 c=c-c CH2 + 1 CH₂ H H H ehz by - leaving group, is iodine (better than Broj This carbocation is stabilized thebbert of 2 et3 groups. typer conjugation ebbect of six ebout of six hydongens. Resonance stabilized

C-C-2 CH3 en 3 CH₂ 1-c-cach2 $ 1- AC - CE - 10 -=CH₂ - H HH CH3 H le leaving group is iodine. stabilized by ore This carbo cation is ti effut CH3 group and and it is also stabilized by there hyperconjugative my daggens. This carbocation is also resonance stabilized. en (Primary Carlocation) No stability From the above studies, clear that the halo alkane expected to react the fastest typical SN' reaction. Comparative it is would be in a