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

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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

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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

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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