Organic Chemistry Lab Activity 1: Molecular Models of Hydrocarbons
For each of the following substances:
a) Draw an electron dot diagram.
a) Construct a model using the kits provided.
b) Using your model as a guide, draw a 3-D diagram for the starred compounds.
1. * propane
2. * propene
3. * propyne
4. 1-butene
5. 2-butene
6. 2-methylbutane
7. 2,3-dimethylbutane
8. * propadiene
Questions:
1. Define the following
a) saturated hydrocarbon
b) unsaturated hydrocarbon
c) straight chain
d) branched chain
9. * butadiene (2 ways)
10. cyclobutane
11. * cis-1,2-dimethylcyclobutane
12. 1,3-cyclopentadiene
13. * cis-2-butene
14. * trans-2-butene
15. 3-ethyl-2-pentene
16. * 1,3,5-cyclohexatriene
e) carbon ring
f) isomer
g) geometric isomers, cis-trans isomers
h) benzene (include a diagram)
2. Draw the electron dot diagrams for each of the following. The name given is
incorrect. Determine the correct name for each of the following.
a) 1,2-dimethylethane
b) 2-methyl-3-propylbutane
c) 2,3,3-triethylpentane
d) 3-propyl-1-pentene
e) 5-hexene
f) 2-ethyl-4-pentene
g) 2,4,6-trimethylhexane
h) 2-propyl-3-methyl-1-propene
i) 2,7-dipropyloctane
j) 3,3-dimethyl-5-heptyne
3. We learned that the general formula for alkanes is CnH2n+2. What is the general
formula for a) alkenes? b) alkynes?
4. Using the models you built in #2 and #3
a) What do you notice about the shape of the six atoms involved in and around a
double bond?
b) What do you notice about ht shape of the four atoms involved in and around a
triple bond?
c) Do you think that this is important to the molecules reactivity?
5. Explain two common mistakes that could be made while writing names for
compounds from the structure.
Naming alkenes and alkynes
Recall: Alkenes are hydrocarbons that contain at least one C-C double bond. Alkynes are
hydrocarbons that contain at least one C-C triple bond.
We use the same general method as used with alkanes to name alkenes and alkynes, except
there is one additional step. We must indicate the location of the multiple bond.
Step 1: Find the longest chain of carbons that contains the multiple bond.
Step 2: Number the chain so that the multiple bond is on the lowest possible number. We give
the multiple bond the number of the lowest carbon it is attached to.
Step 3: Figure out the side groups, as with naming alkanes.
Step 4: Write the name, using the same rules as with alkanes, except that you must number the
multiple bond, just before the main part of the name.
Some examples:
CH3
1.
The longest chain, containing the multiple bond. This
has seven carbons.
CH3-CH2-CH=CH-CH2-CH-CH3
CH3
2.
Number the chain to get the multiple bond on the
lowest possible carbon. In this case we number from
left to right to get multiple bond on the 3rd carbon.
(Multiple bond is between the 3rd and 4th carbon.)
3.
Side groups: There is a side group on the 6th carbon.
It is a methyl group.
4.
Name it: 6-methyl-3- heptene.
CH3-CH2-CH=CH-CH2-CH-CH3
1
2
3
4
5
6
7
CH3
CH3-CH2-CH=CH-CH2-CH-CH3
---------------------------------------------------------------CH3
1. Longest chain: 8 carbons.
2. Numbering: From left to right.
CH3-C-C≡C-CH-CH3
3. Side groups: 2 methyl groups, one on 2nd carbon,
one on 5th carbon.
CH2-CH2-CH3
4. Name: 2,5-dimethyl-3-octyne.
--------------------------------------------------------------------------------------------1. Longest chain: 8 carbons (CH3 in brackets is a side
group!
CH3-CH2-CH=C(CH3)-CH2-CH=CH-CH3 2. Numbering: From right to left. This way we get the
multiple bonds on the lowest numbers
possible, 2 and 5.
3. Side groups: One methyl group on 5th carbon.
4. Name: 5-methyl-2,5-octadiene (The di refers to the
fact that there are two multiple bonds. The ‘a’ is
simple there to make it easier to say.)