Ch 334                                                             Name_____________________________________

Midterm #2

November 21, 2001

 

1.    (4 pts)  Consider the properties of the following compounds:

 

 

NAME

 

FORMULA

 

BOILING PT (oC)

 

MOLECULAR WEIGHT

 

Ethane

 

CH3CH3

 

-88.2

 

30

 

Fluoromethane

 

CH3F

 

-78.6

 

34

 

Methanol

 

CH3OH

 

+64.7

 

32

 

 

Why does methanol boil so much higher than ethane or fluoromethane even though they all have nearly equal molecular weights?

 

 

 

 

2.    (2 pts)  Consider the structure shown below.  Is the conformation given a cis or trans isomer?

 

 

 

 

 

 

 

 

 

3.    (2 pts)  Complete the formula for the most stable conformation of cis-1,3-dimethylcyclohexane.  You only need to draw in the groups that are at positions 1 & 3 as was done in question #2.

 

 

 

 

 

 

 

 

 

 

4.    (2 pts)  Consider the molecule shown at the right:

 

(a)  Draw the other chair conformation of this molecule.

 

 

 

 

 

 

 

 

(b)  Circle the conformation above that is present in greater concentration in the equilibrium  mixture.

 

 

5.    (6 pts)  The following names are incorrect IUPAC names.  Draw the structure implied by this name, indicate why the given name is incorrect and write the correct name for each structure.

 

(a)  2-methylcyclohexene

 

 

 

 

 

 

 

 

(b)  1,2,2-trichloro-4-pentene

 

 

 

 

 

 

 

6.    (4 pts)  In the equilibrium below, the strongest acid is __________________.

 

H2SO4   +  (CH3)2CHOH    D    HSO4-  +  (CH3)2CHOH2+

                                                  

 

 

 

       7.  (6 pts)  Give IUPAC names for the following compounds:

 

(a)   

 

                                             

 

 

 

 

 

_________________________________________________

 

 

(b) 

 

 

 

 

 

 

 

 

_________________________________________________

 

8.    (6 pts)  Circle any of the alkene structures shown below which have geometric isomers.

 

 

 

9.    (6 pts)  Assign E/Z configurations to each of the following alkenes.

 

 

_______                                                   _______                                                         _______

10.  (6 pts)  Give the alkenes that can form from acid-catalyzed dehydration of the following alcohols.  If more than one product can form, identify the products as major or minor. 

 

(a) 

 

 

 

 

 

       (b)  

 

 

 

 

11.  (4 pts)  Although you have not seen reactions involving the following species, your background knowledge concerning nucleophiles and electrophiles is enough to answer this question. Indicate whether the following species would be expected to react as nucleophiles or electrophiles.  Justify your choice.

 

(a)  :Cl+     __________________  Reason:

 

 

(b)  (CH3)3C:-  __________________  Reason:

 

 

 

12.  (8 pts)  Identify the Species I and II as electrophiles (E) or nucleophiles (Nu) in the reactions:

Species I             Species II

 

(a)                 (CH3)2O:        +     B(CH3)3         --------->      (CH3)2O-B(CH3)3

 

_______             _______

 

(b)                 :CN:-              +     CH3Br           ---------->       H3C:CN  +  :Br:-          

 

_______             ________

 

 

 

 

 

 

13.  (16 pts)  Circle the compound in each group that fits the description provided.

 

(a)  Has the lowest Heat of Hydrogenation

 

 

(b)  Has the highest Heat of Combustion

      

       (c)  Is lowest in energy.

 

 

 

 

 

 

 

 

 

 

 

 

(d)  Is most stable.

 

 

 

 

14.  The reaction of tert-butyl bromide with ethanol shown below is termed a solvolysis reaction and gives the products formed.

 

 

Experiment shows that when the concentration of t-butyl bromide is doubled without          changing the amount of ethanol, the rate of reaction doubles.  When the concentration of            tert-butyl bromide is held constant and the concentration of ethanol doubled, no change in the reaction rate is observed.

 

(a)  (6 pts) Draw a mechanism showing how 2-methylpropene forms that is consistent with the kinetic data presented above.  DO NOT COMBINE STEPS IN YOUR MECHANISM.  You must use arrows to show all electron movement.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(b) (4 pts)  Draw a potential energy diagram depicting the intermediates and transition states involved in the reaction. 

 

 

 

 

 

 

 

 

(c) (2 pts) What is the rate determining step of the reaction?

15.     (6 pts)  Draw the most stable chair conformation for the two molecules shown below. One of these stereoisomers undergoes elimination on treatment with sodium ethoxide in ethanol much more readily than the other.  Circle the one which reacts faster.

 

 

      

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                    

    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

16.  (10 pts)  Complete the following reactions by showing the MAJOR organic product.

 

 

    

 

 

 

 

 

 

 

 

Bonus Question (10 pts):

 

Dehydration of cyclohexylmethanol in the laboratory was found to yield three different alkene products. One of these products was cycloheptene.  Draw a mechanism that clearly shows how this product forms.