Question

4. a) In the following substitution reaction, circle and clearly label the individual atoms that perform the following roles: Nucleophile, Electrophile, and Leaving Group. Br OCH2CH3 Ethanol +HBr b) What effect on the overall rate of this reaction would result if the starting concentrations of both 2-bromo-2- methylbutane and ethanol were halved? c) What general effect on the overall rate of this reaction would result if the solvent were changed from acetone to 2-propanol? d) Draw an Energy versus Reaction Coordinate diagram for the reaction shown in 4a (and below). Show the structure of the transition state.

Answer 1

4. LABR Br + + CH3 -CH2 – OH - CH₃-CH 2 - 0 OCH₂ CH3 MONDADOR + HBr as Nucleophile: Ethanol (CH3 CH2OH) sety Electrophile : le Leaving group: In eressante Mechanism of the reaction, I Can B r ( OCH,CHE a - sloas SOCH₂CH2 A Lower , Lucas It fast. + HBO This reaction follows Syl pathway as the reactant produces a very stable tentiary carbocation intermediate.

by bate = K [2-kromo - 2-methylbutane] As the nate determining step involves only the neactant molecule, therefore the rate of the beaction depends only on the concentration of 2- bonomo-2-methylbutane. Now, if we had halved the stanting concen- tration of leath the 2-benomo-2-methyllontane and ethanol the bate of the peaction cwill be half with respect to of the precedows. > Sya beaction pred prefens to oceup in a protre solvent. Acetone is an apnotic solwent. whereas 2- propanol is a protre solvent which will enhance the Guenall nate of the beaction. TS-I Intermediate 7 +8Et +BO - - a -- ABR+ Ethanot AEryn LAOCH2 C.My + HBR Reaction . Coopdinate

strueture of T.SD-I_ 11119 Structure of T. SI