GOC Assignment 2

CHM 1321A
Assignment #2 Answers
1) Which of the following structures represent the same compound?




2) Correct the error in each of the following
H
a) C CH3
C = one carbon missing in the line structure
H2 C
H2


b) H structure shows H connected to carbon and O with one bond
C OH = HO
H2 C C
H2 H O OH

proper way
H O O
c) C CH3 =
O C extra carbon in the line structure
H2




1

, H H
d) charged atom in wrong place
HC C CH HC C CH2
= H2C C CH2 H2C C CH
H2 H2

e) [CH3CH2CH2CH2]+ =

too many carbons (5)

3) Draw complete molecular orbital structures for the following molecules using the LCAO method.
Label the atomic orbitals used to make bonds. Label the bonds. Indicate the geometry of each atom.
(answers at the end of the document)
(a) CH3CH2NH2 (b) CH3CO2H (c) CH3CHCHCH2CH3 (d) CH3OCH3 (e) CH3CN
(f) CH3OCOCH2- (g) CH3NH3+

4) The double bond between the carbon and oxygen in CH3COCH3 is made by mixing various orbitals
from each atom.
a. Draw the molecular orbital energy diagram for the ! bond. Show the representation so the
bond as a molecular orbital, and in the LCAO format.
!" !" molecular orbital



sp2 of oxygen has lower energy than
carbon because oxygen is more
C sp2 electronegative than carbon

O sp2



! molecular orbital
!

sp2 sp2

carbon oxygen
b. Draw the molecular orbital energy diagram for the " bond. Show the representation so the
bond as a molecular orbital, and in the LCAO format.
!" !" molecular orbital



p of oxygen has lower energy than carbon
because oxygen is more electronegative
than carbon
Cp

O p



! molecular orbital
!


carbon oxygen
2