CH2-Cycloalkanes

按环的连接方式
2. Nomenclature of Cycloalkanes
H C H C H H H H C C H H C C H H H C H H CH2 H CH2 CH2 Cyclopropane H C H H C H C H H C C HH H H CH2 CH2 CH2
CH2 CH2 Cyclopentane
蝴 蝶 式
Cyclopentane
信 封 式
CnH2n
O2
CO2 + H2O + HEAT
Heat per CH2
KCal/mole
Cyclopropane Cyclobutane Cyclopentane Cyclohexane Cycloheptane
166.6
162.7
157.3
156.1
H
trans-1,2-dimethylc-1,2-dimethylcyclopropane
Stereoisomers : Such compounds, which have their atoms connected in the same way but differ in three-dimensional orientation, are called stereoisomers.
环丙烷
CH2 CH2 CH2 CH2 Cyclobutane H H H
环戊烷
H C C C C H H H H C C H H CH2 H H CH2 CH2 Cyclohexane CH2 CH2 CH2
环丁烷
环己烷
More examples
CH2 CH2 CH CH3 CH3
CH2 CH2 Methylcyclopentane CH2 CH2 CH2 CH Br 3-Bromocyclohexene Br CH CH
+ Br2 Br Br
(3) Oxidation of cycloalkenes
O3 Zn/H2O
CH3COCH2CH2CH(CH3)CHO
2. Special reactions of small cycloalkanes
(1)Addition of hydrogen to open rings
cis-1,4 trans-1,4
1248.3 1246.8 1245.7 1247.4 1247.4 1245.8
TRANS CIS
TRANS
Which has lower energy?
H
H
CH3 CH3 H
H CH3
CH3
Trans
Which has lower energy?
H H CH3 CH3
角张力（Angle Strain）
Extra potential energy that a cyclic molecule may possess because bond angles are distorted in order to form a ring.
Cyclobutane (puckered form)
小环（C3、C4) 按环大小 普通环（C5－C7） 中环（C8－C12） 大环（>C12) 单环: 如 按环数
CH2 CH2
环数：使环状化合物 变成开链化合物所需 打破的碳碳键的数目。
(环己烷）
CH2 (环丙烷）、
二环：如
(十氢萘）又叫二环[4.4.0]癸烷 多环：二环以上。 如 金刚烷 螺环：共有1个碳 如 稠环：共有2个碳 如十氢萘 桥环：共有2个以上碳原子 如
H2,Ni CH CH CH 3 2 3 80 C H2,Ni CH CH CH CH 3 2 2 3 120 C H2,Ni CH3CH2CH2CH2CH3 300 C
(2) Addition of X2 and HX to open rings
+ Br2 + HBr
BrCH2CH2CH2Br CH3CH2CH2Br
Cyclohexane
No angle or torsional strain
Cyclohexane
staggered
Cyclohexane
Cyclohexane
no contact
Chair Conformation
Chair conformation
push up here
Boat conformation
区别：环丙烷对氧化剂（如高锰酸钾）稳定，而 烯烃易被氧化(Difference:cyclopropane is stable to oxidants(KMnO4), while alkene is easy
to be oxidized)
2.2.4 Conformation of Cyclohexane
CH3 CH3
1,1-Dimethylcyclohexane
CH3 CH3 CH3 CH2
4-Ethyl-1,1-dimethylcyclohexane
CH3 CH3
CH CH3
1-Isopropyl-2-methylcyclohexane
CH3 CH2 C CH3
CH2 CH3
3-Cyclobutyl-3-methylpentane
Cycloalkyl Groups
Cyclopropyl
Cyclobutyl
Cyclopentyl
Cyclohexyl
Nomenclature of Monocycloalkenes
1. Number from the carbon of double bond
2. Indicate substituents using the lowest possible numbers
Cis or Trans?
H CH3 H CH3
Trans
Cis or Trans?
CH3 CH3 H H
Cis
Cis or Trans?
CH3 H H CH3
Cis
Cis or Trans?
CH3 H H CH3
Trans
Isomeric Dimethylcyclohexanes
cis-1,2
Cyclopropane
H C H
105.5
H C H
0.1524nm
C H H
114
环丙烷为张力环，采取重叠式构象，所以容易破环。 此外，环丙烷C－C键为弯曲键，有点类似于烯烃的 键，可以发生类似于烯烃的加成反应。(cyclopropane has ring stain, eclipsed conformation, orbital overlap is less effective, contains more p orbital character)
Nomenclature of the Substituted Monocycloalkanes
If there is only one substituent, do not use the “1”. If there is more than one substituent, you must use all numbers, including “1”! Number around the ring in a direction to get from the first substituent to the second substituent by the shorter path. For equivalent degrees of substitution, number in a direction that follows the alphabetical sequence. A carbon with greater substitution has precedence in numbering.
CH3 CH3 CH3 CH3 C H H
Equatorial methyl
Anti or Gauche?
Anti
Cis or Trans?
H CH3 H CH3
Trans
Axial or equatorial methyl group?
Axial
Cis or trans methyl groups?
Cyclobutane has no such reaction at room temperature!!!
Addition of cyclopropane deritatives with HX should obey Markovnikov Rule.
CH3 + HBr
CH3CHBrCH2CH3
Cis
Predominant conformation of cyclohexane derivatives (环己烷衍生物优势构象的判定)
1.
2.
3.
环己烷一取代物以取代基处于e-键上的最稳 定(One substituent should be in the equatorial) 含相同取代基的环己烷多元取代物最稳定的 构象是e-取代基最多的构象(For identical substituents, more substituents in the equatorial are more stable) 环上有不同取代基时，大的取代基在e-键上 的最稳定(different substituents,large substituents should in the equatorial)
157.0
Estimate of Angle Strain
Number of Carbons Hcomb/CH2 (Hcomb/CH2) - 659 3 4 5 6 7 8 9 10 12 14 697 686 664 659 662 664 665 664 660 659 38 27 5 0 3 5 6 5 1 0