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Table 3 Crystal data and PIXEL energies of polymorphs of Pbtl

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

Form

I

II

III

V a

VI

X b

References

[26]

[26]

[26]

This work

This work

[25, 48]

CCDC refcode

PHBARB07

PHBARB08

PHBARB09

–

–

LATMEA

Space group

P21/n

P \(\overline{1}\)

P21/c

P21/n

P21/n

C2/c

Z′

3

3

1

2

2

1

a (Ã…)

10.70

10.74

9.55

12.76

14.67

12.67

b (Ã…)

47.26

23.40

11.85

6.76

6.90

20.69

c (Ã…)

6.80

6.72

10.81

26.85

23.03

10.25

α (°)

90

91.0

90

90

90

90

β (°)

94.2

94.5

111.6

98.8

94.1

118.5

γ (°)

90

88.4

90

90

90

90

T exp (K)

298

173

298

173

173

173

D (g cm−3)

1.349

1.376

1.357

1.348

1.327

d

HBS

C-2 + L-3

C-2 + L-3

C-2

C-3

C-5

C-1

[N o, N t]

[4/3, 4/3]

[4/3, 4/3]

[0, 2]

[4, 0]

[2, 1]

[0, 2]

m.p. (°C) [26]

176

174

168

160

156

126

E T,Cry/ΔE intra (kJ mol−1)

c/7.3

c/7.5

−118.3/3.9

−122.4/13.1

−114.9/3.7

−118.3/8.0

E T,Σ (kJ mol−1)

−123.3

−122.4

−120.5

−124.1

−117.9

−121.1

E T,Σ(A)/ΔE intra (kJ mol−1)

−143.1/8.9

−141.4/8.7

–

−120.9/8.5

−128.3/0.3

–

E T,Σ(B)/ΔE intra (kJ mol−1)

−103.8/6.9

−104.0/8.2

–

−127.4/17.6

−107.5/7.1

–

E T,Σ(C)/ΔE intra (kJ mol−1)

−122.9/6.0

−121.9/5.5

–

–

–

–

Density order

3rd

1st

2nd

4th

5th

d

Stability order (RT) [26]

1st

2nd

3rd

4/5th

4/5th

e

Stability order (calc.)f

2nd

3rd

1st

6th

4th

5th

  1. aThe matrix (\(100 00\overline{1} \overline{1} 0\overline{1}\)) transforms the room temperature data reported by Williams [36] (a = 12.66, b = 6.75, c = 27.69 Å; β = 106.9°; P21/c) into a unit cell (a′ = 12.66, b′ = 6.75, c′ = 26.89 Å; β’ = 99.9°; P21/n) which matches our data
  2. bThe structure model for form X (Additional file 1: Section 8) was derived from the isostructural co-crystal of Pbtl with pentobarbital (the quoted CCDC refcode, unit cell data and T exp all refer to the co-crystal)
  3. c E T,Cry not determined because of Z′ > 2
  4. dNot applicable
  5. eExists only in a melt-film preparation and in the presence of a structurally analogous second barbiturate
  6. fBased on the results of SCDS-PIXEL calculations, corrected for ΔE intra