Easy Baby
Chemistry S-20
Week 1
Alkenes: Isomers and Nomenclature
1. There are 6 unique alkene isomers of the hydrocarbon C5H10. Draw each of these isomers, and provide a systematic name for each.
1-pentene
(E)-2-pentene
(Z)-2-pentene
2-methyl-1-butene
2-methyl-2-butene
3-methyl-1-butene
2. For the three alkenes above which are various isomers of pentene, rank them in order of stability. Explain your ranking.
most stable (more subst. double bond)
less stable (cis alkene is slightly less stable)
least stable (less substituted double bond)
3. Provide a systematic name for the following alkene.
(Z)-3-propyl-2-heptene
32
Chemistry S-20
Week 2
Bicyclic Compounds and Bredt's Rule
1. Draw each of the following bicyclic compounds in a good "perspective" drawing.
CH3
CH3
trans-decalin: two chairs
CH3
CH3
CH3
norbornane skeleton:
CH3 H3C CH3
2. The molecule trans-cyclooctene is known to exist. (It is chiral, by the way). Why is the analagous molecule trans-cyclohexene unstable? Far too strained to have a trans-alkene in a six-membered ring.
H H H
=
H
H H
trans-cyclooctene (planar representation)
trans-cyclooctene (perspective representation)
trans-cyclohexene????
3. Draw each of the following bicyclic alkenes in a good "perspective" representation. Only one of these three compounds actually exists. Which one, and why?
BAD!
In these two, the alkenes can't be planar. Highly strained. (Try to model!)
BAD!
Ok! ** Bredt's Rule: Can't have sp2 carbon at a bridgehead. (No alkenes, no carbocations!)
Or, notice the trans-alkenes in small rings.
60
Chemistry S-20
Week 1
Carbocation Stability
1. Draw the structure of the methyl cation, CH3+. Describe the hybridization, geometry, and orbitals in this species.
H H
H
Carbon is sp2-hybridized, with 120° bond angles and a vacant p-orbital.
2. Each of the following carbocations is significantly more stable than
Week 1
Alkenes: Isomers and Nomenclature
1. There are 6 unique alkene isomers of the hydrocarbon C5H10. Draw each of these isomers, and provide a systematic name for each.
1-pentene
(E)-2-pentene
(Z)-2-pentene
2-methyl-1-butene
2-methyl-2-butene
3-methyl-1-butene
2. For the three alkenes above which are various isomers of pentene, rank them in order of stability. Explain your ranking.
most stable (more subst. double bond)
less stable (cis alkene is slightly less stable)
least stable (less substituted double bond)
3. Provide a systematic name for the following alkene.
(Z)-3-propyl-2-heptene
32
Chemistry S-20
Week 2
Bicyclic Compounds and Bredt's Rule
1. Draw each of the following bicyclic compounds in a good "perspective" drawing.
CH3
CH3
trans-decalin: two chairs
CH3
CH3
CH3
norbornane skeleton:
CH3 H3C CH3
2. The molecule trans-cyclooctene is known to exist. (It is chiral, by the way). Why is the analagous molecule trans-cyclohexene unstable? Far too strained to have a trans-alkene in a six-membered ring.
H H H
=
H
H H
trans-cyclooctene (planar representation)
trans-cyclooctene (perspective representation)
trans-cyclohexene????
3. Draw each of the following bicyclic alkenes in a good "perspective" representation. Only one of these three compounds actually exists. Which one, and why?
BAD!
In these two, the alkenes can't be planar. Highly strained. (Try to model!)
BAD!
Ok! ** Bredt's Rule: Can't have sp2 carbon at a bridgehead. (No alkenes, no carbocations!)
Or, notice the trans-alkenes in small rings.
60
Chemistry S-20
Week 1
Carbocation Stability
1. Draw the structure of the methyl cation, CH3+. Describe the hybridization, geometry, and orbitals in this species.
H H
H
Carbon is sp2-hybridized, with 120° bond angles and a vacant p-orbital.
2. Each of the following carbocations is significantly more stable than