Organic Chemistry (1)
Examination
CI073-01
April 1, 1998
1. Write the Lewis structure for each of the following compounds, and draw all possible resonance structures and rank them in order
of their relative importance.
(a) methyl isocyanate (CH3NCO)
(b) protonated acetone (CH3COHCH3+)
(c) enolate of formaldehyde (HCOCH2-)
(d) dimethyl sulfoxide (CH3SOCH3)
2. Write Lewis structures for these ions. Show all valence electrons and all formal charges.
(a) ethanoate ion (CH3CO2-) (b) borohydride ion (BH4-)
(c) azide ion (N3-)
3. Each of the following molecules contains one principal functional group. Locate and name the group, and classify the molecule
for each case.
(a)
H2C CH 2
H2C
C O
H2C CH 2
H2C
H2
O
(b) H3C C C C OH
CH 3
H2
C
H2C
CH OH
(c)
H2C C
H2
4. Rank the following compounds in order of increasing acidity and explain the order.
(a) CH3OH, CH3CO2H
(b) HNO2, HNO3
(c) CH3CO2H, CH3CH2CO2H, ClCH2CO2H
5. Give the IUPAC name for each of the following compounds.
6. Provide your explanation for each of the following phenomena or observations.
(a) Cyanic acid, HOCN, and isocyanic acid, HNCO, dissolve in water to yield the same anion on loss of H+.
(b) 4-Pentanedione is considerably stronger acid than is propanone (acetone).
O
O
(c)
(d)
H3CC
CH 2CH 3C H
H3CC
Propanone
O
CH H
2,4-Pentandione
In methyl cyclohexane, the chair conformation having the methyl group in equatorial position is more stable than one
having the methyl group in the axial position.
Acetylene anion is a lot more stable than the ethylene anion.
7. Construct a potential energy diagram for rotation about the C-2C-3 bond of 3-bromopropane. For each unique energy
maximum or minimum, illustrate the structure with a Newman projection.
8. Draw the most stable conformation for each of the following compounds.
(a) trans-1,2-dimethylcyclohexane
(b) trans-1,4-dichlorocyclohexane
(c) trans-1,3-di-tert-butylcyclohexane
9. Assign R or S to each stereocenter.
Cl
HO
H3C
HO
(c)
(b)
(a)
H
HOH2C
H
COOH
10. Write structure for each of the following compounds using Fischer projection.
(a) (S)-2-butanol
(b) (3S,4R)-3chloro-4-methylhexane
11.
Provide a concise yet complete definition for each of the following terms.
(a) quaternary carbon
(b) envelope conformation
(c) dispersion force
(e) inductive effect
(f) dextrorotatory
(g) specific rotation
(d) torsional strain