CHEM 123- Set 9 & 10 Notes

set 09


D conformations :
diff .
atom arrangement due to
I>
Newman projections
C C single bonds
rotating
-




H

( change in connectivity ?
f
no H H
H H
-
,



eclipsed staggered
→ µ"
"
"


µxµ H
-


H
H H H 1
H H H H H

9nH H


⑥ •H e
'
" "
Hi
"µ staggered
H H
H H
↳
dihedral angle o
HIGH energy Low
energy →
"
☐
conformations of butane
" 1-1,1
/
-
↳ rotational energy
-180°
"
^
Mir H
-




MY
eclipse
, ;D H >
f
,
H H



staggered eclipse
*




① anti
giiaiuche It torsional strain )
1 I
to
I 1 I
-




180 -120 -60 60 120 180 Me
Me Pr OH
EX '




OH
Hµ →
/
\H /
ex lowest F-
highest
:
.
to
F
CHZCH } H CHIH } CHZCH } CHZCH , ,
Hgc
H \ Hf ) H \ F
, -
H / H

-
H
-
H Meo CHO
y
H
CH H
f H
H OHC


|
H H H H H I M
,
Hsc ,



w
anti
✗
eclipsed
y
gauche
z
syn
→
#
A- ipr Me
"
⑥ ==§
2 > ✗ > Y > w o bonds /
Me
-




H H H
y µ
↳ size & temperature dependence of rotation

•

t size of substituent groups ( bulky groups ) D cis / trans for cyclo

hinder rotation "
relativ
"
=
↳ sides are


t temperature the ring ( think d
•
=
rotation more difficult
F
ex ,




D cyclo alkanes 1
F
↳
alkane
rings are not flat ( only cyclopropane )
strain bond angles orbital
ring geometry can overlap
↳ +

'=

strain due to deviation from bond angles
angle strain
:
↳




↳
cyclohexane chair :
F
F
Ma =
equatorial
-1 f
/ Ma = axial