S1
Polymorphism in acesulfame sweetener: Structure-property and stability relationships of bending and brittle crystals
Sitaram P. Velaga,*a Venu R. Vangala,a,,c Srinivas Basavoju,a and Dan Boströmb aDepartment of Health Sciences, Luleå University of Technology, Luleå S-971 87, Sweden; bEnergy Technology and Thermal Process Chemistry, Umeå University, Umeå S-901 87, Sweden. cCurrent Address: Institute of Chemical and Engineering Sciences, A*STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island,Singapore, 627833, Singapore.
Electronic Supplementary Information (ESI) (10 pages)
Table of contents
(i) Preparation of neutral acesulfame S1
(ii) Thermal profiles of acesulfame needle and prismatic crystals S2
(iii) Vibrational spectroscopy for Forms I and II S3
(iv) ORTEP plots, overlay of conformations, hydrogen bond
geometries for Forms I and II
S4
(v) Face indexing for acesulfame Forms I S5
(vi) Simulated PXRD patterns for Forms I and II S6
(vii) Product phase of Form II quenched at 110°C S7
(viii) Slurry of acesulfame - product phases DSC and PXRD S8
(ix) DSC profile of heat-cool-heat for Form II S9
(x) Lattice energy calculations for Forms I and II S10
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S2
S1. Neutralization of Acesulfame potassium (Ace K).
It was obtained from Sigma Aldrich at a stated purity of 99% and no attempt was made at further purification. Ace K (5 g) was dissolved in water (5 mL), neutralized with concentrated HCl (5 mL) and achieved the highly acidic solution of ~ pH =2 and extracted with ethyl acetate (15 mL). Up on routine work up afforded a white solid of salt free acesulfame. It was crystallized from EtOAc by slow evaporation at the ambient conditions. Needle crystals were yielded. Mp: 122-124 °C.
S2 DSC and TGA for the needle and the prismatic crystals.
40 60 80 100 120 140 160 180-14
-12
-10
-8
-6
-4
-2
0
2
Needle crystals
DSC
TGA
Temperature (oC)
Hea
t Flo
w (W
/g)
70
75
80
85
90
95
100
Weight %
50 75 100 125 150 175 200
-14
-12
-10
-8
-6
-4
-2
0
2
DSC
Temperature (oC)
Hea
t Flo
w (W
/g)
40
50
60
70
80
90
100
70 80 90 100
-0.36
-0.32
-0.28
Hea
t Flo
w (W
/g)
Temperature (oC)
Prismatic crystals
TGA
Weight %
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S3
S3a. Raman vibrational spectroscopy for acesulfame Form I.
wavenumbers1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
283.
134
037
7.442
4.5
470.
850
0.9
520.
153
3.4
542.
4
641.
5
731.
7
798.
385
4.490
4.8
928.
497
4.7
1033
1158
1197
1266
1387
1417
1440
1662
1690
Acesulfame Form I
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S4
S3b Raman vibrational spectroscopy for acesulfame Form II.
wavenumbers1600 1400 1200 1000 800 600 400
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
225.
428
0.7
339.
238
1.4
421.
347
049
7.7
521.
255
2.9
638.
2
736.
679
5.1
860.
9
926.
8
1029
1196
126613
9214
2414
42
1669
Acesulfame Form II
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S5
S4a ORTEP plots at the 50% probability level. Two and one independent molecules in the asymmetric unit of Forms I and II respectively.
Form I
Form II
S4b Molecular conformations of acesulfame Forms I and II. While Form I adopts two different conformations (Blue and Green), Form II conformation (pink) was similar to one of the indpentent molecules of Form I (Blue).
Form I Form II
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S6
S4c Hydrogen bond geometries for Forms I and II.a
D–H⋅⋅⋅A d(H⋅⋅⋅A)/ Å d(D⋅⋅⋅A)/ Å ∠( D–H⋅⋅⋅A)/ ° Symmetry code
Form I
N–H⋅⋅⋅O
N–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
1.74
1.77
2.29
2.37
2.39
2.41
2.63
2.66
2.69
2.70
2.7349(19)
2.717(2)
3.341(2)
3.372(2)
3.338(3)
3.436(3)
3.634(3)
3.552(2)
3.583(2)
3.547(2)
169
156
163
153
145
157
155
140
139
135
2-x,-1/2+y,1/2-z
1-x,1/2+y,1/2-z
-1+x,y,z
x,1/2-y,1/2+z
2-x,-1/2+y,1/2-z
1+x,y,z
1-x,1/2+y,1/2-z
1+x,y,z
-1+x,y,z
1-x,-y,1-z
Form II
N–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
C–H⋅⋅⋅O
1.77
2.49
2.65
2.67
2.68
2.7722(18)
3.516(2)
3.395(2)
3.604(2)
3.665(2)
169
157
125
145
151
1-x,1-y,-z
x,-1+y,z
1-x,-y,1-z
-x,-y,-z
-x,-y,1-z
aN-H and C-H geometries were normalized.
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S7
S5 Face indexing of acesulfame Forms I.
S6 Simulated X-ray powder patterns obtained from the single crystal structures of Forms I and II.
10 20 30 40
0
2000
4000
6000
8000
10000
12000
14000
Brittle simulated
Bending simulated
Inte
nsity
(arb
itrar
y un
its)
2θ
Form I
Form II
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S8
S7 Form II quenched at 110 °C and recorded the PXRD. It was shown to be Form I.
10 20 30 40
0
500
1000
1500
Quenched PXRD
Inte
nsity
(arb
itrar
y un
its)
2θ
S8a Slurry of Forms I and II. Product phase PXRD shown to be Form I.
A 50:50 (w/w) mixture of Forms I and II was stirred in CH3OH at room temperature RT for 72h and the filtrate was dried at 30 °C for 24h
5 10 15 20 25 30 35 400
1000
2000
3000
4000
5000
6000
Post slurry PXRD
Form I
Inte
nsity
(arb
itrar
y un
its)
2θ
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S9
S8b DSC trace for the product phase from the slurry experiment. Note the complete transformation to Form I.
40 60 80 100 120 140-10
-8
-6
-4
-2
0133.6 J/g120.53 oC
122.05 oC
Forms I and II (50+50% w/w) slurried for 72h
Product Phase = Form I
Hea
t Flo
w (W
/g)
Temperature (oC)
S9 DSC profile of heat–cool–heat for Form II. It suggests that enantiotropic transformation is non-interconvertible under the investigated conditions.
-20 0 20 40 60 80 100 120 140-1.0
-0.5
0.0
0.5
-20 oC to 110 oC @ 10 oC/min
110 oC to 25 oC @ 10 oC/min
25 oC to 140 oC @ 10 oC/min
DSC of Form II: Heat - cool - heat
Hea
t Flo
w (W
/g)
Temperature (oC)
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010
S10
S10. Lattice energy calculations for Forms I and II
Lattice energy calculation for Forms I and II was performed using the Forcite module in the Materials Studio. Single crystal X-ray structure co-ordinates were minimized by the COMPASS force field. The charges were assigned by the force field. The Ewald summation employed to compute the non-bonded interactions that include van der Waals and electrostatic interactions. Finally, lattice energies were computed per molecule based on the number of molecules present in the unit cell (See also: A. Nangia, Acc. Chem. Res. 2008, 41, 595-604 and references cited there in).
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2010