CHEM 240: Survey of Organic Chemistryat North Dakota State University Practice Exam 2 Questions

!1. (a) In the following reaction of the addition of HCl to vinylcyclopentane (1), one of the major products formed is 1-chloro-1-ethylcyclopentane (2). The mechanism for this reaction involves the formation of intermediate A which is converted into intermediate B and finally the product 2 is formed. In the boxes below, draw the structures of the intermediates showing any charges that are present.

intermediate A intermediate B

Cl

1 2(step 1) (step 2) (step 3)

HCl

(b) The following reaction energy diagram describes the reaction above. On the diagram, label the position of each compound in the reaction including the starting material 1, the product 2, and intermediates A and B. Also, please draw a circle around all transition states.

Label 1, 2, and intermediates A and B

Circle all Transition StatesE

reaction progress

(c) Is the reaction above exothermic or endothermic?

(d) Which step is the rate determining step?

(e) Why does the intermediate A convert into intermediate B?

Chem 240 Practice Exam 2 Problems! page 1! fall 2016

2) Draw the product for the reactions below using 1-methylcyclopentene as the starting material.

3) For each of these two steps of this reaction mechanism, draw the curved arrows (on the species below) showing how the electrons move in the bond breaking and bond making.

C C

H

H H

H+ H Br C C

H

HH

H+ Br

H

C C

H

H H

H

HBr

draw arrows on thesefor the first step

draw arrows on thesefor the second step

step 1 step 2

4) Draw the structure for the major organic product for each of the following reactions. Please make sure to show any stereochemistry clearly.

Chem 240 Practice Exam 2 Problems! page 2! fall 2016

5) For each of the following molecules, indicate the number of stereogenic centers and check whether the molecule is achiral or chiral.

NH

O

HOOH

OH

OH

Number ofStereogenic

Centers Chiral Achiral

Br

HH

Cl

CO2HHO2C

HO OH

OH Cl

Cl

CH3

H3C

HO

Number ofStereogenic

Centers Chiral AchiralCheck One Check One

6) Arrange these carbocations in order of increasing stability (least to most).

7) Which is the product of the reaction of 1-methylcyclohexene with H2O/H2SO4?

8) Which compound does not give two stereoisomers when reacted with Cl2?

Chem 240 Practice Exam 2 Problems! page 3! fall 2016

9) Determine the R or S configuration for the following:

10) What is the relationship between the following pairs of molecules, enantiomers, diastereomers or identical?

a) b)

c) d)

e) f)

g) g)

Chem 240 Practice Exam 2 Problems! page 4! fall 2016