CHE 132 Fall 2001
Hydrocarbons
Workshop Exercise
1. Formulas and drawings. There are several different ways that chemists use to represent
molecules. Here are some examples.
Structural
Formula
3D
Representation
Line Drawing
Condensed
Structural
Formula
Molecular
Formula
H
H C
H
H C
C
H CH3
H
H
H
CH3CH(CH3)2
C4H10
C H
H H
H H H
H
H C
H
H
C C
C
HH
CH3
CH3
H
H
H H H H
CH3CH=CHCH3
C4H8
H
What are the advantages and disadvantages of each type of representation?
Structural formulas show the connectivity, but not the 3D geometry, 3D representations show geometry but are
hard to draw, line drawing are a good compromise. Condensed structural diagrams are good for showing on a
line, but are hard to interpret, The molecular formula says nothing about strucuture
Here are some molecules represented in one of the four ways. Give the other four representations
for each example.
H H H H
H C
H
C
C C
H
H C
H H
H
H
a.
b.
c. C3H8
H CH3H H
H
d.
H CH3 H H
H
e.
CH3CH2CH(CH3)CH2CH3
2. You can tell a lot about an organic compound by looking at its molecular formula. Here are some
examples.
Alkane
Hydrocarbon with only C-C single bonds. Alkanes have the general formula CnH2n+2.
Alkene
Hydrocarbon with one C-C double bond. Alkenes have the general formula CnH2n.
Alkyne
Hydrocarbon with one C-C triple bond. Alkynes have the general formula CnH2n-2.
Cycloalkane Hydrocarbon with only C-C single bonds with one ring. Cycloalkanes have the general
formula CnH2n.
Each time you take away two hydrogen atoms from an alkane you either must add a pi bond or a ring.
For example an alkane with four carbon atoms would have the formula C4H10. A compound with the
formula C4H6 is missing two pairs of H atoms. It thus has two pi bonds, two rings or one pi bond and
one ring. The following compounds are examples of C4H6 compounds.
H
Can you draw some additional C4H6 isomers?
Draw as many molecules as you can with the formula C5H10.
3.
Name each of the following compounds.
a.
d.
4.
b.
e.
Draw structures (line structures) for each of the following.
a.
2,3-dimethylheptane
b.
4-methyl-2-octyne
c.
4-ethyl-2,4-dimethylnonane
d.
methylcyclobutane
e.
trans-1,2-dimethylcyclobutane
c.
f.
5. Draw all possible isomers of hexane, C6H14.
6. Starting with your answers to question 5 as a guide. Draw all possible isomers of C6H13Cl.
7. What is the molecular formula of each of the following molecules?
a. Cholesterol
HO
C27H46O
O
H
N
O
H
S
CH3
CH3
N
O
O
HO
b. Penicillin V
C16H18N2O5S
8. What is the hybridization (sp, sp2 or sp3)of each carbon atom in each of the following?
a.
O
N
b.
O
N
c.
H
CH3