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Table 4 Sums of internal energies, E HBS,Σ (kJ mol−1), from N–H···O=C bonded structures in polymorphs of Pbtl and their origin from different types of interaction

From: Specific energy contributions from competing hydrogen-bonded structures in six polymorphs of phenobarbital

HBS

Form

N HBS [N o, N t, N n]

E HBS,Σ

E T range (o)

E T range (t)

E n,Σ

C-1

X

2 [0, 2, 0]

−47.5

 

−47.2 to −47.7

 

C-2

III

2 [0, 2, 0]

−45.4

 

−45.4

 

C-2

I (C)

2 [0, 2, 0]

−48.9

 

−48.1 to −49.7

 

C-2

II (C)

2 [0, 2, 0]

−46.9

 

−46.8 to −47.0

 

C-3

V

4 [4, 0, 0]

−56.4

−23.1 to −32.9

  

C-5

VI

6 [2, 1, 3]

−72.0

−28.4 to −34.4

−46.5

−17.3

L-3

I (A + B)

10 [2, 1, 7]

−100.2

−34.0 to −40.5

−49.2

−38.4

L-3

II (A + B)

10 [2, 1, 7]

−98.6

−35.1 to −38.2

−45.7 to −47.5

−38.7

  1. Contributions arise from N HBS pairwise contacts, of which there are N o one-point H-bond connections, N T two-point connections and N n non-H-bond interactions and ranges of interaction energies E T (kJ mol−1) for the o- and t-connections involved. E n,Σ (kJ mol−1) is the sum of all significant (internal) non-H-bonded interaction energies within an HBS (C-5 and L-3 only)