Form, function and functionality of two dimeric toluene-2,4-diisocyanate polymorphs

2,4-Dioxo-1,3-diazetidine-1,3-bis(methyl-m-phenylene) diisocyanate (dimerized toluene-2,4-diisocyanate, TDI) is one of the most widely used aromatic diisocyanates in the polymer industry, and it crystallizes in at least two polymorphic forms (form A and form B) depending on reaction conditions. The crystal structures of the two forms were determined from high-resolution laboratory X-ray powder diffraction data using simulated annealing and Rietveld refinement. In spite of a marked structural similarity between them, significant discrepancies in the physical properties of the two forms prompted analysis of their partitioned energy terms in an effort to better our understanding of the driving force behind such differences in behaviour.

Computing details

Figures

(TDIC01) toluene-2,4-diisocyanate

Crystal data

C18H12N4O4	β = 81.6029 (15)°
Mr = 348	γ = 81.2337 (13)°
Triclinic, P1	V = 391.75 (1) Å^3
a = 4.53125 (8) Å	Z = 1
b = 5.99235 (8) Å	Cu Kα radiation, λ = 1.54059 Å
c = 14.7567 (3) Å	T = 298 K
α = 88.2562 (12)°	?, ? × ? × ? mm

Data collection

Bruker D8 ADVANCE diffractometer	Scan method: step
Specimen mounting: Capillary	2θmin = 5.0°, 2θmax = 68.3°, 2θstep = 0.009°
Data collection mode: transmission

Refinement

Refinement on F^2	Profile function: Calculated from fundamental parameters
Rp = 0.036	63 parameters
Rwp = 0.050	47 restraints
Rexp = 0.015
χ^2 = NOT FOUND	Background function: Chebychev polynomial
7362 data points

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.3493 (11)	0.1024 (10)	1.0115 (4)	0.04245
N2	0.5466 (4)	0.0707 (5)	0.9318 (2)	0.04245
O3	0.1186 (8)	0.2393 (6)	1.0302 (3)	0.04245
C5	0.6337 (3)	0.2109 (3)	0.8649 (1)	0.04245
C8	0.5141 (3)	0.4354 (3)	0.8508 (1)	0.04245
C9	0.8690 (3)	0.1268 (4)	0.8017 (1)	0.04245
C13	0.6320 (3)	0.5599 (4)	0.7764 (1)	0.04245
H14	0.3337 (16)	0.5084 (12)	0.8974 (5)	0.05094
C15	1.0001 (2)	0.2467 (4)	0.7238 (1)	0.04245
H16	0.9282 (17)	−0.0406 (10)	0.8224 (5)	0.05094
C21	0.8758 (3)	0.4810 (4)	0.7085 (1)	0.04245
H22	0.5375 (17)	0.7325 (11)	0.7670 (4)	0.05094
N23	1.2526 (4)	0.1486 (5)	0.6586 (2)	0.04245
C27	0.9887 (5)	0.6274 (5)	0.6288 (2)	0.04245
C28	1.4796 (14)	0.2074 (12)	0.6035 (3)	0.04245
H31	1.1710 (14)	0.7320 (15)	0.6186 (2)	0.05094
H32	0.987 (5)	0.530 (3)	0.5644 (6)	0.05094
H33	0.773 (2)	0.731 (2)	0.6171 (18)	0.05094
O34	1.5660 (11)	0.2222 (8)	0.5312 (3)	0.04245

Geometric parameters (Å, º)

O3—C1	1.229 (7)	C13—C21	1.412 (2)
O34—C28	1.087 (6)	C21—C27	1.521 (3)
N2—C5	1.332 (3)	C8—H14	1.038 (7)
N23—C28	1.301 (6)	C13—H22	1.071 (7)
C5—C8	1.393 (2)	C27—H32	1.132 (11)
C5—C9	1.355 (2)	C27—H33	1.108 (11)
C8—C13	1.396 (2)
N2—C5—C8	128.46 (17)	C5—C8—H14	118.1 (4)
N2—C5—C9	116.62 (19)	C13—C8—H14	120.6 (4)
C8—C5—C9	114.92 (16)	C8—C13—H22	120.2 (4)
C5—C8—C13	121.35 (15)	C21—C13—H22	113.7 (4)
C8—C13—C21	126.1 (2)	C21—C27—H32	106.2 (7)
C13—C21—C27	122.9 (2)	C21—C27—H33	100.0 (11)
O34—C28—N23	142.1 (6)	H32—C27—H33	89.3 (16)

(TDIC02) toluene-2,4-diisocyanate

Crystal data

C18H12N4O4	β = 99.7115 (6)°
Mr = 348	γ = 114.0050 (6)°
Triclinic, P1	V = 770.56 (1) Å^3
a = 9.09477 (8) Å	Z = 2
b = 7.45366 (5) Å	Cu Kα radiation, λ = 1.54059 Å
c = 12.75989 (16) Å	T = 298 K
α = 93.5753 (8)°	?, ? × ? × ? mm

Data collection

Bruker D8 ADVANCE diffractometer	Scan method: step
Specimen mounting: Capillary	2θmin = 5.0°, 2θmax = 67.4°, 2θstep = 0.009°
Data collection mode: transmission

Refinement

Refinement on F^2	Profile function: Calculated from fundamental parameters
Rp = 0.019	150 parameters
Rwp = 0.025	104 restraints
Rexp = 0.012
χ^2 = NOT FOUND	Background function: Chebychev polynomial
7268 data points

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.0703 (4)	0.7858 (7)	0.3017 (3)	0.04011
N2	0.2307 (4)	0.8069 (5)	0.3074 (3)	0.04011
O3	−0.0331 (4)	0.7936 (5)	0.2318 (3)	0.04011
N4	0.0699 (4)	0.7589 (5)	0.4111 (3)	0.04011
C5	0.3247 (4)	0.8023 (3)	0.2331 (3)	0.04011
C6	0.2320 (4)	0.7805 (7)	0.4170 (3)	0.04011
C7	−0.0349 (4)	0.7428 (4)	0.4810 (3)	0.04011
C8	0.4932 (4)	0.8636 (3)	0.2670 (3)	0.04011
C9	0.2510 (4)	0.7340 (3)	0.1275 (3)	0.04011
O10	0.3391 (4)	0.7768 (5)	0.4910 (3)	0.04011
C11	−0.1903 (4)	0.7282 (4)	0.4456 (3)	0.04011
C12	0.0211 (4)	0.7419 (3)	0.5860 (3)	0.04011
C13	0.5879 (4)	0.8557 (3)	0.1948 (3)	0.04011
H14	0.5511 (14)	0.9174 (18)	0.3498 (11)	0.04813
C15	0.3499 (4)	0.7301 (4)	0.0555 (3)	0.04011
H16	0.1171 (15)	0.6822 (18)	0.0999 (13)	0.04813
C17	−0.2898 (4)	0.7111 (3)	0.5161 (3)	0.04011
H18	−0.2344 (15)	0.7314 (18)	0.3619 (12)	0.04813
C19	−0.0797 (4)	0.7254 (4)	0.6611 (3)	0.04011
H20	0.1474 (15)	0.7576 (18)	0.6119 (13)	0.04813
C21	0.5195 (4)	0.7890 (3)	0.0876 (3)	0.04011
H22	0.7204 (14)	0.9077 (18)	0.2248 (11)	0.04813
N23	0.2597 (4)	0.6579 (5)	−0.0496 (3)	0.04011
C24	−0.2407 (4)	0.7089 (4)	0.6270 (3)	0.04011
H25	−0.4075 (17)	0.6980 (18)	0.4848 (14)	0.04813
N26	−0.0092 (5)	0.7234 (5)	0.7693 (3)	0.04011
C27	0.6218 (4)	0.7851 (4)	0.0097 (3)	0.04011
C28	0.2965 (5)	0.6435 (7)	−0.1378 (3)	0.04011
C29	−0.3540 (4)	0.6866 (4)	0.7065 (3)	0.04011
C30	−0.0409 (5)	0.7544 (7)	0.8574 (3)	0.04011
H31	0.5585 (17)	0.6578 (17)	−0.0518 (13)	0.04813
H32	0.6552 (14)	0.9230 (16)	−0.0237 (12)	0.04813
H33	0.7292 (14)	0.7817 (19)	0.0511 (14)	0.04813
O34	0.3068 (4)	0.6249 (5)	−0.2279 (3)	0.04011
H35	−0.3927 (16)	0.5402 (18)	0.7350 (11)	0.04813
H36	−0.2883 (14)	0.808 (2)	0.7742 (11)	0.04813
H37	−0.4597 (15)	0.6999 (18)	0.6664 (12)	0.04813
O38	−0.0507 (5)	0.7736 (5)	0.9447 (3)	0.04011

Geometric parameters (Å, º)

C1—N2	1.391 (5)	C13—C21	1.372 (5)
C1—O3	1.205 (6)	C13—H22	1.093 (14)
C1—N4	1.423 (5)	C15—C21	1.398 (5)
N2—C5	1.387 (5)	C15—N23	1.393 (5)
N2—C6	1.423 (5)	C17—C24	1.413 (5)
N4—C6	1.405 (6)	C17—H25	1.040 (17)
N4—C7	1.388 (5)	C19—C24	1.407 (5)
C5—C8	1.388 (5)	C19—N26	1.425 (5)
C5—C9	1.362 (5)	C21—C27	1.478 (5)
C6—O10	1.247 (6)	N23—C28	1.238 (6)
C7—C11	1.366 (5)	C24—C29	1.534 (5)
C7—C12	1.352 (5)	N26—C30	1.238 (6)
C8—C13	1.377 (5)	C27—H31	1.076 (15)
C8—H14	1.069 (14)	C27—H32	1.084 (12)
C9—C15	1.397 (5)	C27—H33	1.040 (16)
C9—H16	1.101 (15)	C28—O34	1.173 (5)
C11—C17	1.356 (5)	C29—H35	1.108 (13)
C11—H18	1.081 (15)	C29—H36	1.100 (14)
C12—C19	1.412 (5)	C29—H37	1.055 (15)
C12—H20	1.096 (16)	C30—O38	1.137 (5)
C1—N2—C5	135.3 (4)	C11—C17—C24	123.2 (4)
C1—N2—C6	85.6 (3)	N26—C19—C12	116.1 (3)
C5—N2—C6	137.2 (3)	N26—C19—C24	123.8 (3)
C1—N4—C6	85.1 (3)	C12—C19—C24	120.1 (3)
C1—N4—C7	136.9 (4)	C13—C21—C15	116.9 (3)
C6—N4—C7	137.7 (4)	C13—C21—C27	121.3 (3)
C15—N23—C28	134.3 (4)	C15—C21—C27	121.8 (3)
C19—N26—C30	134.2 (4)	C17—C24—C19	115.7 (3)
O3—C1—N2	133.9 (4)	C17—C24—C29	123.2 (3)
O3—C1—N4	131.0 (4)	C19—C24—C29	121.1 (3)
N2—C1—N4	95.0 (3)	O34—C28—N23	169.6 (5)
N2—C5—C8	119.8 (3)	O38—C30—N26	168.9 (5)
N2—C5—C9	120.0 (3)	C5—C8—H14	120.2 (8)
C8—C5—C9	120.2 (4)	C13—C8—H14	119.1 (8)
O10—C6—N2	132.4 (4)	C5—C9—H16	120.9 (9)
O10—C6—N4	133.2 (4)	C15—C9—H16	121.0 (9)
N2—C6—N4	94.4 (3)	C7—C11—H18	120.6 (9)
N4—C7—C11	121.4 (3)	C17—C11—H18	119.6 (9)
N4—C7—C12	118.0 (4)	C7—C12—H20	118.6 (9)
C11—C7—C12	120.5 (4)	C19—C12—H20	120.7 (9)
C5—C8—C13	120.7 (3)	C8—C13—H22	118.2 (8)
C5—C9—C15	118.1 (3)	C21—C13—H22	120.5 (8)
C7—C11—C17	119.8 (3)	C11—C17—H25	116.7 (10)
C7—C12—C19	120.8 (4)	C24—C17—H25	120.1 (10)
C8—C13—C21	121.3 (3)	C21—C27—H31	111.8 (9)
N23—C15—C9	112.4 (3)	C21—C27—H32	107.1 (8)
N23—C15—C21	124.8 (4)	C21—C27—H33	108.4 (10)
C9—C15—C21	122.9 (3)	H31—C27—H32	111.8 (11)
H31—C27—H33	109.4 (12)	C24—C29—H37	107.8 (9)
H32—C27—H33	108.2 (11)	H35—C29—H36	111.0 (10)
C24—C29—H35	111.7 (8)	H35—C29—H37	108.8 (11)
C24—C29—H36	108.3 (8)	H36—C29—H37	109.2 (11)