Rotation um Einfachbindungen
Tab. 1 Rotationsbarrieren von C–C-Einfachbindungen Tab. 2 Stabilität von Konfomeren
Egauche -Etrans
Barrier Gas Liquid
Compound kJ/mol kcal/mol Compound X Y kJ/mol kcal/mol kJ/mol kcal/mol
CH3–CH2X XCH2–CH2Y CH3 CH3 4.0 0.96 3.2 0.76
X = H 12.1 2.88 Cl Cl 4.6 1.1 0 0
X = F 13.9 3.33 Br Br 6.3 1.5 –2.9 0.7
X = Cl 15.4 3.68 Br Cl 5.9 1.4 –2.1 0.5
X = Br 15.4 3.68 CH3 Cl –0.2 –0.05 0.2 0.05
X = I 13.4 ± 2.1 3.2 ± 0.5 CH3 Br –0.63 –0.15 – –
CH3–CF3 12.7 3.04 Cl OH –4.0 –0.95 –4.0 –0.95
CH3–CCl3 12.2 2.91
DF3–CCl3 25.1 6.0 XCH2–CH2Y Cl Cl 0 0 –4.6 –1.1
(CH3)3C–C(CH3)2X Br Br – – –4.0 –0.95
X = H 29.2 6.97 Solution in CF2Cl2
X = F 33.7 8.04 kJ/mol kJ/mol
X = Cl 43.7 10.43 H 1.2 0.29
X = Br 44.9 10.73
(CH3)2C C(CH3)2
H X F –1.9 –0.45
X = I 46.6 11.14 Cl 0.42 0.10
Br 0.88 0.21
I 2.3 0.56
Positive Werte bedeuten eine Bevorzugung der anti-Konformation
