CHEM 342. Spring 2002.  PS#8 Answers   PS#6 Answers    PS#7 Questions    PS#7 Answers.doc (Word 97)  

  

Problem Set #7 Answers

 

Note: Relevant Chapter in Mortimer is Chapter 18 and Appendix I.

Symmetry Operations; Schoenflies Symbols for Point Groups; Group Theory

For the problems #1-14, please list the Schoenflies symbols and symmetry elements for each of the following molecules. Also state whether or not each molecule is optically active or if it has a permanent dipole moment. Hint: The Schoenflies symbols   and have the symmetry elements and   respectively.

 

1.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: Yes

 

2.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: Yes

 

3.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

4.

Schoenflies symbol:

Symmetry elements:

Optically Active: Yes

Permanent Dipole Moment: Yes

 

5.

1,3,5-tribromobenzene

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

6.

Schoenflies symbol:

Symmetry elements:

Optically Active: Yes

Permanent Dipole Moment: Yes

 

7.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: Yes

 

8.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

9.

p-dichlorobenzene

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

10.

cyclohexane

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

11.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

12.

CO

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: Yes

 

13.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

14.

Schoenflies symbol:

Symmetry elements:

Optically Active: No

Permanent Dipole Moment: No

 

Note: An optically active molecule must belong to the point groups A molecule with a dipole moment must belong to the point groups

15. State if a orbital is symmetric or anti-symmetric with respect to the following operations

  1. reflection across the xy plane
  2. reflection across the xz plane
  3. reflection across the yz plane
  4. operation
  5. operation
  6. inversion (i) operation
  7. rotation about the x-axis
 
  1. symmetric
  2. symmetric
  3. anti-symmetric
  4. ani-symmetric
  5. anti-symmetric
  6. anti-symmetric
  7. symmetric, this is a axis

 

16. State if a orbital is symmetric or anti-symmetric with respect to the following operations

  1. inversion, i

 

  1. symmetric
  2. anti-symmetric
  3. anti-symmetric
  4. anti-symmetric
  5. symmetric
  6. anti-symmetric
  7. anti-symmetric
  8. symmetric

 

17. Which, if any, of the following point groups have a permanent dipole moment?

    Of the above groups, the groups have a permanent dipole.

 

18. Which, if any, of the following point groups show optical activity?

None of these groups are optically active.