Chapter 11 Alkenes and IR I. Alkene Nomenclature A. Unsaturation 1) Alkanes: C n H 2n+2 2) Alkenes: C n H 2n 3) Degree of Unsaturation a) Tells us how many rings and double bonds in molecule b) H sat = 2C + 2 – X + N (Ignore O, S) c) Degree of Unsaturation = (H sat – H act )/2 d) Example: C 5 H 8 NOCl i. H sat = 2(5) + 2 – 1 + 1 = 12 ii. (H sat – H act )/2 = (12 – 8)/2 = 2 degrees of unsaturation C C C H H H H H H H H C C C H H H H H H C N O H C C C C H H H H H Cl H H
12
Embed
Chapter 11 Alkenes and IR I.Alkene Nomenclature A.Unsaturation 1)Alkanes: C n H 2n+2 2)Alkenes: C n H 2n 3)Degree of Unsaturation a)Tells us how many rings.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Chapter 11 Alkenes and IR
I. Alkene NomenclatureA. Unsaturation
1) Alkanes: CnH2n+2
2) Alkenes: CnH2n
3) Degree of Unsaturation
a) Tells us how many rings and double bonds in molecule
b) Hsat = 2C + 2 – X + N (Ignore O, S)
c) Degree of Unsaturation = (Hsat – Hact)/2
d) Example: C5H8NOCl
i. Hsat = 2(5) + 2 – 1 + 1 = 12
ii. (Hsat – Hact)/2 = (12 – 8)/2 = 2 degrees of unsaturation
C C C
H
H
H
H
H
H
H
H
C CC
H
H
HH
H
H
C N
O
H
C C CC
H
H
H H
H
Cl
H
H
B. Nomenclature
1. Common Names end with –ylene
a. Ethylene
b. Propylene
2. IUPAC: Replace –ane of an alkane with –ene of an alkene
a. Ethene
b. Propene
3. Alkenes follow alkane nomenclature, with double bond location numbered closest to end
a. 1-butene
b. 2-butene
c. Cylclohexene
4. Substituents named as prefixes with lowest numbers
a. 3-methyl-1-pentene
b. 3-methylcyclohexene
C C
H
H
H
HC C
C
H
H
HH
H
H
C CCH2 CH3
H
H
HH3C C
C CH3
H
H
5. Disubstituted Alkenes can be cis or trans streoisomers
a. cis-2-butene
b. trans-2-butene
c. Cycloalkenes cis unless large
6. Tri- or Tetra-substituted Alkenes can be E or Z stereoisomers
a. Use priorities from R/S nomenclature
b. Assign 1-2 on each carbon
c. Move from 1-2-1-2 to trace out an E or Z
7. Alcohols have priority over alkene in numbering: Alkenol