NAME   _______________________   CHEM 311  EXAM I  Fall 2001 Sect 002

 

1.  Draw the electronic configuration of  S    1s2 ___________________________ .
  
S has   ______ valence electrons and ( adds, gives up ) _____ electrons to
    become a stable octet.

 

  1. Each atomic orbital has a maximum of ____ electrons.  The unpaired electron in Cl combines the similar unpaired electron of the second Cl  to form a ( s ,  p  ) covalent bond.

 

  1. Electrons within an atom combine to form __________ orbitals while electrons of different atoms combine to form ___________ orbitals and  _________ orbitals. Both have a maximum of ____ electrons and combine with another similar type orbital to form (covalent, ionic)  bonds.

 

  1. Determine whether the following pairs of structures are actually different compounds or simply resonance forms of the same compound:

         

  1. The following compound can become protonated on any of the three nitrogen atoms.  One of these nitrogens is much more basic than the others, however.

                 

    1. Draw the important resonance forms of the products of protonation on each of the three nitrogen atoms.
    2. Determine which nitrogen atom is the most basic.

               

    

  1. In the following, draw important resonance forms. Indicate the major and minor contributors or would be of equal value. Explain.

                     

 

  1. Predict the products of the following acid-base reaction and indicate the extent of reaction (explain):

        a.    (CH3)3 NH+1   +    CH3-O-1       «                       +         

            (acid, base)    (acid, base)            conjugate      +            conjugate                                                                 (acid, base)                (acid, base)

      approx pKa _____         ______              _______                      _______

 

  1. Match the following structures with the name of their functional group:

 

    ____a. alkanes        ____f. amide               1.  C6H14   6.  RCºCH

    ____b. alcohol         ____g.amine               2.  RNH2     7. RCH=CHR’

 

    ____c. alkyne          ____h. ester                3.  RCOOH   8.  RC=OOR’      

 

    ____d. aldehyde      ____i. alkyl halide        4. RCl          9.  ROH

 

    ____e. nitrile          ____j. carboxylic acid    5. RC=O NH2   10. RCN

 

  1. In 2-pentyne there are four carbon atoms in a straight line.  Use dashed line and wedges to draw a three dimensional representation of this molecule, and circle the four atoms that are in a straight line.

 

 

 

 

 

b. Indicate the hybridization and geometry of each carbon atom.

 

10.  Sulfur dioxide ( SO2 )  has a dipole of 1.6 D while carbon dioxide  ( CO2  ) 
    has a dipole of  0.0  D, even thought   the C-O  bonds are more polar 
   
than S-O bonds.  Explain this apparent contradiction.

 

 

 

11. Dimethyl sulfoxide ( DMSO ) has been used as an anti-inflammatory rub for
    race horses.  DMSO and acetone seem to have similar structures, but the C=O
    carbon atom in acetone is planar, while the S=O in DMSO is pyramidal. Draw
    correct Lewis Structures for DMSO and acetone, predict the hybridizations and
    explain these observations.

             

 

 

12. Rank the following species in order of increasing basicity ( #1 least basic).
    Explain your reasons for ordering them as you do.

 

            ___ CH3-   ____ CH3COOH   ___  NaOH     ___ NH2-   ____HSO4  -

       

13. N-Methylpyrrolidine has a boiling point of 81oC and piperidine has a boiling
    point of 106oC. 

 

    1. Explain this large difference ( 25 degrees C )  in boiling point for these two isomers.

 

 

 

        b.  Tetrahydropyran has a boiling point of 53oC and cyclopentanol  has a
            boiling point of 141oC.  These two isomers have a boiling point difference
            of   53oC.  Explain why the two oxygen-containing isomers have a much
                larger
boiling point difference than the amine isomers.

             

 

 

14.  Draw the Newman projection of   trans-3-isobutyl-1-methylcyclohexane, draw
    the  two regular chair conformers and indicate which ( if any ) conformer is the
    major conformer at equilibrium. Explain your answer.

 

 

 

 

  1. Draw (line-angle formulas) of all 5 structural isomers with the empirical formula C3H6O.  Name them by their functional group only.

 

 

 

 

 

  1. Explain the use of heats of combustion to determine the strain energy of cyclopropane versus cyclohexane. Where and why is there more strain in these two compounds?