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Morphology of sodium bromate (NaBrO3) under the influence of purified sodium dithionate (Na2S2O6)

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HAL Id: hal-01938524

https://hal-normandie-univ.archives-ouvertes.fr/hal-01938524

Submitted on 12 Dec 2018

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Morphology of sodium bromate (NaBrO3) under the influence of purified sodium dithionate (Na2S2O6)

M. Schindler, Clément Brandel, G. Coquerel

To cite this version:

M. Schindler, Clément Brandel, G. Coquerel. Morphology of sodium bromate (NaBrO3) under the influence of purified sodium dithionate (Na2S2O6). 43èmes JEEP, Mar 2017, Barcelone, Spain. �hal- 01938524�

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Manon SCHINDLER*, Clément BRANDEL, Gérard COQUEREL

Normandie Univ, Laboratoire SMS-EA3233, Univ Rouen, F76821, Mont-Saint-Aignan, France.

*manon.schindler@etu.univ-rouen.fr

References:

[1] Kipping, F. S., Pope, W. J., J. Chem. Soc. Trans., 73, 606–617 (1898).

[2] Surender, V., Arundhathi, N., Rao, K. K., Bull. Mater. Sci., 29 (5), 427–432 (2006).

[3] Lan, Z.-P., Lai, X., Roberts, K., Klapper, H., Cryst. Growth Des. 14 (11), 6084–6092 (2014).

[4] Schlessinger, G.G., Inorganic laboratory preparations, Chemical Publishing Company, 58-59 (1962).

[5] Larson, D. W.; VanCleave, A. B. Can. J. Chem. 1963, 41 (2), 219–223.

[6] Holcomb, E. R.; Inoue, T.; Nishioka, K. J. Cryst. Growth 1996, 158 (3), 336–339.

Morphology of sodium bromate (NaBrO 3 ) under the influence of purified sodium dithionate (Na 2 S 2 O 6 )

SYNTHESIS & CHARACTERIZATION OF Na 2 S 2 O 6

Synthesis 4

Reaction involved:

Step I: Na 2 SO 3 + 2AgNO 3  Ag 2 SO 3 + 2NaNO 3

Step II (oxidation-reduction reaction)*: Ag 2 SO 3 + Na 2 SO 3  Na 2 S 2 O 6 + 2Ag

Experiment: Reagents mixture is kept 30 min under stirring and boiling. White precipitate of Ag 2 SO 3 disappears and Ag crystallizes. After filtration of silver, solution of dithionate is concentrated by evaporation of solvent. Crystallization of dihydrated dithionate is induced by addition of antisolvent (ethanol and acetone). Yield: 75%

*Involved oxidation-reduction reaction: Strongest oxidizing agent (Ag + ) reacts with the weakest reducing agent (SO 3 2- ).

2Ag + + 2e -  2Ag E° = 0,800 V

(+I) (0)

2SO 3 2-  S 2 O 6 2- + 2e - E° = 0,514 V

(+IV) (+V)

2Ag + + SO 3 2- + 2Na + + SO 3 2-  2Na + + S 2 O 6 2- + 2Ag

Characterization of synthesized product

THE MORPHOLOGIES OF SODIUM BROMATE 3

Effect of sodium dithionate on sodium bromate ?

NaClO 3

Morphodrome of NaBrO 3 as a function of the crystallization temperature and supersaturation 6

 At high temperature and high supersaturation, NaBrO 3 crystals can present a cubic habit. 6

Effect of Na 2 S 2 O 6 on cubic morphology of NaBrO 3 ?

INTRODUCTION

NaClO 3 and NaBrO 3 present isomorphous structures (same space group P2 1 3 and same atomic positions in the unit cell). 1 Although the two substances are achiral, crystals of NaClO 3 and NaBrO 3 both show supramolecular chirality. However, the crystal habits of NaClO 3 and NaBrO 3 differ: NaClO 3 crystals exhibit large cubic {100} faces while NaBrO 3 crystals exhibit tetrahedral {111} faces. 2

SUPRAMOLECULAR CHIRALITY

INFLUENCE OF Na 2 S 2 O 6 ON NaClO 3

Habit modification of NaClO 3 by addition of

Na 2 S 2 O 6

Enhancing the {111}

tetrahedral faces and

suppressing the {001}cubic ones 3

PROSPECTS

AKNOWLEDGMENTS

Synthesis and characterization of Na 2 S 2 O 6

• Improve yield of synthesis and recrystallization

NaBrO 3 / Na 2 S 2 O 6 system

• Reconsider experimental conditions to well control of NaBrO 3 crystallization

• What will be the effect of Na 2 S 2 O 6 on expected cubic crystals of

NaBrO 3 ? Will effects be the same (twins by inversion) than on NaClO 3 cubic crystals ?

NaBrO 3

The use of a pair of polarizer can easily evidence the occurrence of levo and dextro enantiomorphic crystals.

(100)

Crystals of NaClO 3 from aqueous solution observed under polarized light.

Crystals of NaBrO 3 from aqueous solution observed under polarized light.

(111) (111)

(111)

(111)

Crystallization of NaClO 3 from aqueous solution in presence of Na 2 S 2 O 6 (molar ratio 1/1000)

Formation of NaClO 3 twin of opposite

handedness 3

Crystal of NaClO 3 showing the tetrahedral morphology.

Obtained by evaporation of solvent at room temperature.in presence of Na 2 S 2 O 6 .

Twinned crystal of NaClO 3 showing two opposite handedness obtained by evaporation of solvent at room temperature in

presence of Na 2 S 2 O 6 .

This work was funded by the Normandy region and European regional development fund (FEDER).

Re lativ e in tensities

2q (°)

Na

2

S

2

O

6

,2H

2

O

recrystallized in water

Na

2

S

2

O

6

,2H

2

O

commercial batch

XRPD patterns of commercial batch (in black) and synthesized product (in red)

As the sodium dithionate is not easily available, Na 2 S 2 O 6 was synthesized. The synthesized product has been compared with the commercial batch.

TG-DSC of the commercial batch (red) and the synthesized product (green).

Commercial batch and synthesized

product are sodium dithionate dihydrate.

Dehydration occurs at 90°C as described in literature. 5

DSC W/g exo up TG (%)

DSC analyses of different samples of Na 2 S 2 O 6.

Comparison of different purification of synthesized product. (heating rate: 5K/min, closed crucibles)

Recrystallization in water is more efficient to purify Na 2 S 2 O 6 ; the drawback is the low yield (47%).

Crystal of NaBrO 3 obtained from aqueous solution in presence of Na 2 S 2 O 6 (molar ratio 1/1000) by

evaporation of solvent, at room temperature

No significant effect of sodium dithionate on the typical trigonal form of sodium bromate

In sealed vial, required amount of NaBrO 3 to achieve desired supersaturation is dissolved in water and then cooled to crystallization temperature. Without seeding, crystallization occurs in few hours.

T cryst : 45°C / supersaturation: 1.05

Crystals of pure NaBrO 3 .

Crystals of NaBrO 3 in presence of Na 2 S 2 O 6

(molar ratio 0,3%).

 No expected cubic crystals at high temperature and high supersaturation. Crystallization is not well controlled.

 Na 2 S 2 O 6 seems to lead to twinned crystals.

Effect on handedness ?

(011) (111)

D-form L-form L-form D-form

Références

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