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Ch4
saturated
* cycloalkane
1. C
cycloalkane
chain
⇒ alkane
2. number substituents: min
attachment point C₁
3. some substituents can get same numbers
⇒用字母排
* cycloalkane:
1. x rotation
2. CT. rotational freedom T
* Strain energy
1. torsional
2. steric
*cyclopropane
1. most strained
angle
torsional
(Pin) 2. banana bond weaker & more reactive
HH
* cyclobutane :
planar
\H
1. nearly same strain angle less
1.
H
H
H
(8.25)
H
-H
H.
HH
chair conformation: ring-flip:
axial
equatorial
H H
E
H
barrier
H
H
- CEZ mirror
H
H
H/
clockwise
-
H
H
H
H
H
H
ea (up & down (2)
2. not all are equally stable
ex: substituents are more stable at e.
1,3-diaxial interaction
Isteric strain)
4. Substituents size ↑. Strain t
torsional more
3.
(C-HT)
as cyclopropane
2. not planar
* cyclohexane
1. less strain:
angle: min
torsional large
reduce torsional
nonplanar
* decalin
H
H
H
H
3. angle
o 109° (sp³, tetrahedral)
occurs only in small rings
(has little flexibility)
bicyclo[2,21] heptane
(7)
2. chair conformation: most stable: no strain
3. twist-boat conformation: angle: min
H-
torsional large
steric large
cis
H
trans