Download Alkene geometry-KEY_2013 and more Exercises Geometry in PDF only on Docsity!
1 Alkene geometry-ANSWER KEY Chemistry 260 Organic Chemistry
- The answer is 2. The two carbons of the double bond are sp^2 hybridized (planar). Therefore, all carbons lie in the same plane.
- The answer is 4. 3 - ethyl- 2 - pentene
- Give the IUPAC name of 2 - ethyl- 1 - butene
- Give the structural formula of: (a) 2,3-dimethyl- 2 - butene (b) 2,3-dimethyl- 2 - butanol (c) 3 - chloropropene (d) 3 - methyl- 2 - pentanol
H 3 C
C C
H 3 C
CH 3
CH 3
CH 3 CH C
CH 2 CH 3
1 2 3 CH 2 CH 3
C C
H
H
CH 3 CH 2
CH 3 CH 2
4 3 2 1 C C
CH 3 CH 3
CH 3 CH 3
OH
CH 3 CH 3
CH 3 C CHCH 3
C C
H CH 2 Cl H H
OH
CH 3
CH 3 CHCHCH 2 CH 3
- (E)- 2 - pentene
- The answer is 1. H 2 C H 2 C CH 2
CH 2
H 3 C CH 3
H H
H 3 C H
H CH 3
H 2 C CHCH 2 CH 3
H 3 C
CH 2
H 3 C
CHCH 3
H 2 C
H 2 C
- Give the IUPAC name of: (a) cis- 3 - hexene or (Z)- 3 - hexene (b) trans-2,5-dimethyl- 3 - hexene or (E)-2,5-dimethyl- 3 - hexene
C C
CH 3 H
H CH 2 CH 3
1 2 3 4 5 C C
CH 3 CH 2 CH 2 CH 3
H H
1 2 3 4 5 6 C C CH 3
H CH 3
CH
CH 3
CH
CH 3 H
1 2 3 4 5 6
(b) two isomers (e) one isomer C H H
C
H 3 C CH 3
C
H 3 C H
C
H CH 3
(Z) (E)
(c) one isomer C H 3 C H
C
H 3 C CH 3
- Give the structural formula of cis- 2 - methyl- 3 - heptene 1 7. cis- and trans-Isomers of 1,2-dichloroethene can be isolated because C=C (σ + π) bonding is quite rigid. For 1,2-dichloroethane, only a single C-C (σ) bond exists and this is not rigid. Free rotation about the σ bond in 1,2- dichloroethane removes any possibility of distinct cis- and trans-isomers: C Cl H
C
H Cl (E)- 1 , 2 - dichloroethene
C
Cl Cl
C
H H
(Z)- 1 , 2 - dichloroethene Cl Cl 1 , 2 - dichloroethane (rotation about σ-bond is easier than about π-bond)
H
H
H
H
- The answer is 2. C H F
C
H 3 C CH 3
(E)
C
H 3 C CH 2 CH 3
C
H 3 CH 2 C CH 2 CH 3
C C
CH 3 CH CH 2 CH 2 CH 3
H H
CH 3
- E/Z Isomers are only possible when there is a C=C double bond present in the molecule. (a) NO - no double bond present H 3 C C
CH 3
Cl
CH 3
(b) NO - only one orientation possible if triple bond present H 3 C C C CH 3 (c) NO - double bond present, but one C has two identical groups C C
H 3 C H
H
(d) YES - two geometric isomers: C C
H H
CH 3
(Z)
C C
H CH 3
H
(E)
(e) YES - two geometric isomers: C C Cl F Cl H (E)
C C
Cl
F H
Cl (Z)
(f) YES - two geometric isomers: C C H
H 3 CH 2 C CH 3
H
(Z)
C C
H 3 CH 2 C
H CH 3
H
(E)
- Name the following compounds according to the IUPAC rules nomenclature. Indicate stereochemistry where appropriate.
