Table 1 Equilibrium constants of amide cis-trans isomerization at −50 °C

From: Amide nitrogen pyramidalization changes lactam amide spinning

 

Linker length

trans/cis (%)a

K c/t b

ΔΔGcis-trans (25 °C)

6(Z)-NH (CD2Cl2)

C8

<0.1 />99.9c

>999

< −4.10

6(E)-NH (CD2Cl2)

C8

16/84

5.25

−0.98

16 (CD2Cl2)

C8

8/92

11.5

−1.45

17 (CD2Cl2)

C9

14/86

6.14

−1.08

18 (CD2Cl2)

C10

73/27

0.37

+0.59

19 (CD2Cl2)d

C11

86/14

0.16

+1.08

20 (CD2Cl2)

C12

94/6

0.06

+1.63

1 (CD2Cl2)

Open

>99.9/<0.1

<0.001

>+ 4.10

16 (CD3OD)

C8

16/84

5.25

−0.98

17 (CD3OD)

C9

24/76

3.17

−0.68

18 (CD3OD)

C10

77/23

0.30

+0.72

  1. aErrors in the ratios of cis and trans are within ± 1%
  2. bKc/t = [cis]/[trans]
  3. cThe trans rotamer was below the detection limit
  4. dMeasured at −47.8 °C
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