EXAM 1
CHEMISTRY 220
Friday, September 26, 1997

NAME (print): ___________________________________________________

TA:_____________________    Day:_________________ Time:__________


Take a few moments to look over the exam.  Answer each question on the exam paper.

Important points are in bold.

 Do all preliminary drawing or computations on the work sheets at the end of the exam..

The exam is 55 minutes. 

STOP writing when you are asked to do so.

REMEMBER: Neatness is to your advantage.

1. (16 pts)	______


2.  (18 pts)	______


3.  (10 pts)	______


4.  (20 pts)	______


5.  (26 pts)	______


6.  (10 pts)	______

________________________________

Total (100 pts)  

1.	(16 pts) Draw (10 pts) vinylacetylene 1 using p-orbitals to form pi-bonds (other bonds 
may be lines).  Locate sp, sp2, and sp3 hybridized carbons (6 pts).  In a word, how 
would you describe the shape of vinylacetylene?

	            

2.	(18 pts)  Consider the staggered conformations of 2,3-dimethylbutane viewed along the 
C2-C3 bond. [H/H, eclipsed, 1.0 kcal/mol; CH3/H eclipsed, 1.4 kcal/mol; CH3/CH3, 
eclipsed, 2.5 kcal/mol; CH3/CH3, gauche, 0.9 kcal/mol]

	a)  (3 pts)  How many different staggered conformations are there?

	


	



	b)  (6 pts)  Draw them in Newman projections.



















	c)  (6 pts)  Calculate the energy of each one using the values provided and place the value 
below the projection in (b). [Show work]












	d)  (3 pts)  Calculate the energy difference between the least and most stable in (c). 
[Show work]


3.	(10 pts)  Draw a generic structure for each of the following functional groups.

	a)  carboxylic acid





	b)  aldehyde






	c)  ether







	d)  acyl halide







	e)  alkyne


4)	(20 pts)  Circle the best answer for each of the following:


	a)  C-C bond length in an alkane

		1.54 �	1.54 cm	1.33 �	1.1 � 		109o 28'




	b)  C-H bond length when the carbon is sp3 hybridized


		1.54 �	1.54 cm	1.33 �	1.1 � 		109o 28'



	c)  Number the following acids in order of increasing pKa value (lowest = 1).




		HCl 	acetic acid	ethanol	ammonia	cyclohexane




	d)  The name of the 19th century chemist who developed a strain theory for cycloalkanes?


 
		Kekule	Liebig		van't Hoff		Baeyer	Berzelius



	
	e)  Which of the following terms apply to the structure of t-butyl carbocation (CH3)3C+?



		radical 	tetrahedral		linear 		planar		basic

5.	(26 pts)  Complete the following questions relating to the reaction shown below.

				                            
                                                           

	a)  (5 pts)   Label  A, B,   C, AB­, and BC­ on the above diagram.


	b)  ( 5 pts) Show on the diagram the energy barrier that controls the rate of the reaction.  
Label it (b).

	c)  ( 5 pts) Show the energy gap on the diagram that indicates DHo(rxn).  Label it (c).

	d)  ( 6 pts)  Describe the thermicity (endo- or exo-) for:


		A ----> B

		 
		B ----> C

		
		A ----> C


	e)  (5 pts)  Which rate constant is the largest?
	


6.	(10 pts)  Name the compound shown by the IUPAC system.

						                   


				
	Work Sheets

	Work Sheets

	Work Sheets

	Work Sheets