View of X-RAY DIFFRACTION STUDIES OF PRASEODYMIUM CAPRYLATE IN SOLID STATE

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ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING

Peer Reviewed and Refereed Journal, ISSN NO. 2456-1037

Available Online: www.ajeee.co.in/index.php/AJEEE

Vol. 06, Special Issue 01, (IC-RCOVID19) April 2021 IMPACT FACTOR: 7.98 (INTERNATIONAL JOURNAL) 78 X-RAY DIFFRACTION STUDIES OF PRASEODYMIUM CAPRYLATE IN SOLID STATE

Kirti Vishwakarma

School Science, Renaissance University Indore (M.P.) India

Abstract - X-ray diffraction is common technique for the study of crystal structure and atomic spacing. X-ray diffraction is based on constructive interference of monochromatic x- ray and a crystalline sample. The X-ray analysis showed that praseodymium caprylate soaps have double layer structure with molecular axis slightly inclined to the basal plane.

Keywords: praseodymium caprylate , x-ray diffraction, metallic soap, atomic spacing.

1 INTRODUCTION

Carboxylates of metals other than alkali metal are generally insoluble in water and called

“metallic soaps”. The techniques used in for the preparation of metal soaps may be categorize as precipitation method involve the reaction of a soluble salt of the metal with a solution of alkali soap in water. The fusion method generally involves either, (I) a neutralization reaction between the oxide or hydroxide of a metal with a fused fatty acid, or alternatively, (II) a metathatic displacement reaction in which the carbonate or some other salt of the metal such as acetate is treated with fatty acid in a fused state. The metal is chemically bound to anionic head group of fatty acid by both ionic and covalent linkages.

The anionic head group of a fatty acid molecule contains of a terminal carboxylate group.

This terminal group is the chemically charged end of the fatty acid. The terminal carboxylate group has a net electronic charge of minus one (-1). The length and saturation of the fatty acid anion may vary. The physical properties of the solution of metal soaps in organic solvent can be elucidated in term of the micellar theory. Metallic soaps with elements from lanthanide series (La, Ce,-Lu) were synthesized for the first time in early 60s.

These compounds are interesting for their uses as catalyst, emulsifier, cosmetics, plasticizers, lubricant, greases, pesticides, medicines, softeners, flatteners, surface active agents and waterproofing agents. The metal carboxylates or metallic soaps were prepared by several workers^1-4 by reacting the fatty acids with required amount of metallic hydroxide, oxides of metal in presence of an emulsifying agent, wetting agent, organic solvent or an organic base. The method of preparation and properties of lanthanum, cerium, neodymium, gadolinium, soaps were reviewed by Mehrotra and Upadhyaya⁵ .Kapoor et. al.⁶

The structure of sodium soaps of different fatty acids was studied by several workers^7-9 by using X-ray technique. Skoulios et.al.¹⁰ studied the structure of sodium soaps at higher temperature by X- ray diffraction technique and stated that the shape of the unit cell is more symmetrical. Ogino¹¹ confirmed that the structure of sodium salts of saturated fatty acid is monoclinic in symmetry and the inclination of the molecules is about 60⁰ . Vold et. al.¹² characterized heavy metal soaps by X-ray diffraction and demonstrated that most of the soaps could be identified simply from their diffraction petterns. Gallot et.

al.¹³proposed two types of lamellar structures of alkali metal soaps by X-ray diffraction petterns. Bauer et. al.¹⁴ determined the long spacing for aluminium di-soaps. Three distinct crystal phases of potassium soaps at higher temperature were recognized by Luzzati et. al.¹⁵ whereas Kambe¹⁶analysed cobalt soaps by X-ray technique and showed that the red soaps has lamellar strcture while blue salt has a different structure

2 EXPERIMENTAL

2.1 Preparation of Praseodymium Soaps of Saturated Fatty Acids Using Metathesis Method

Analar grade fatty acid (caprylic acid), potassium hydroxide, benzene, methanol, ethanol, acetone and praseodymium acetate 99% (Indian rare-earth limited, Kerala) were used for the present investigations. Potassium soaps (potassium caprylate) were prepared by saponification of corresponding fatty acids with potassium hydroxide in alcohol on a water bath. The soaps were dried in vacuum.

The purity of the soaps was checked by the determination of their melting point, carbon and hydrogen analysis praseodymium acetate was used for converting potassium soaps in to corresponding praseodymium soaps (purity 99% Indian Rare Earth Limited, Kerala). The metal soap were prepared by the direct metathesis of corresponding potassium

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Vol. 06, Special Issue 01, (IC-RCOVID19) April 2021 IMPACT FACTOR: 7.98 (INTERNATIONAL JOURNAL) 79 soaps (potassium caprylate) by pouring a slight stoichiometric excess of aqueous solution of praseodymium acetate in to the clear soap dispersion at raised temperature with constant stirring. An immediate silvery colored precipitate usually formed after the addition of o drop of praseodymium acetate. This precipitate becomes thicker on further addition of praseodymium acetate. Finally producing a good precipitate of praseodymium soaps and leaving non-turbid mother liquor. The following reaction takes place.

(CH3COO)3 Pr + 3RCOOK → (RCOO)3 Pr + 3CH3COOK (Praseodymium soap)

Where R is equivalent to C7H15, for caprylate. Praseodymium soaps, upon precipitation, occluded untreated substances that need to be removed. Occluded substance included minor to trace amount of unreacted free fatty acids and traces of unreacted potassium soaps. In each case, each soap was first filtered using a vacuum pump to assist a speed, through whatman 52 filter paper. The relatively large area of the funnel filter surface ensured that all of the soap was filtered properly. The washing step was first accomplished with lots of doubly distilled water to remove most of remaining Praseodymium acetate and the bulk of any unreacted potassium soaps. Enough water was used to ensure the pH of filtrate was neutral and filtrate showed no sign of containing potassium soap, even a trace of soap in the filtrate, under vacuum led to the formation of forth. A final wash with alcohol and acetone was carried out in order to remove any adherent unreacted fatty acid, potassium soap and traces of potassium and gadolinium salts. After pressing out solvent, metal soaps were first dried in an air oven at 50⁰-60⁰ C and the final drying of soaps was carried out under reduced pressure. Final soaps powdered and stored in glass stoppered bottles at room temperature.

2.2 Apparatus

The X-ray diffraction patterns of praseodymium soaps (praseodymium caprylate) were carried out with a “PXRD- Rlgaku, Smartlab “X-ray diffract meter using Cu-Kα radiation filtered by a nickel foil. The instrument yields an automatically recorded curve of intensity of diffracted x-ray versus angle of diffraction 2θ. Bragg’s spacing corresponding to interplanar separation of the reciprocal crystal lattice, were determined from the peak by using the Bragg’s relationship. The X-ray diffraction analysis was carried out at IIT Indore.

3 RESULT AND DISCUSSION

It is necessary to know about the structures of fatty acids before discussing the diffractograms of the praseodymium soaps (praseodymium caprylate). A fatty acid contains a long paraffin chain of the chain. It is known that the stearic acid molecule consists of a chain lying flat in one plane in which the –CH2 groups forms a zig- zag line. The zig – zag pattern is ascertained by comparing the lengths of any two fatty acid molecules. X-ray diffraction patterns of praseodymium soaps (praseodymium caprylate). Show numerous peaks over the range of 3-80^o diffraction angle. The order of diffraction in these soaps decreases with the decrease in chain-length of the soap. The results show that the crystallinity of these soaps increases with the increase in chain-length of the soap molecules. The calculated values of interplanar spacings for praseodymium metal soaps are recorded in Table 3.2.1. The values of average planar distance i.e. the long spacing for praseodymium caprylate (25.7Å), are somewhat smaller than the calculated dimensions of their corresponding anions i.e. caprylate (27.0 Å) from Paulings values of atomic radii and bond angles. The values of long spacing increase with increasing chain-length (Tables 3.2.1) of praseodymium soap. Therefore, it is concluded the molecular axes of praseodymium metal soaps are somewhat inclined to the basal planes.The praseodymium cation fit into spaces between oxygen atoms of the ionized carboxyl group without giving a large strain of the bond. The difference in the long spacing of metal soaps approximately correspond to double the length of methylene (- CH2) groups in fatty acid radical constituent of the soap molecules. The zig-zag chains of fatty acids radicals extend

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ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING

Vol. 06, Special Issue 01, (IC-RCOVID19) April 2021 IMPACT FACTOR: 7.98 (INTERNATIONAL JOURNAL) 80 in both slides with their axes somewhat inclined to the planes containing the praseodymium ions.

The numbers of peaks corresponding to shorter side spacing in the intermediate range of diffraction angles are also observed in the diffraction patterns of praseodymium soaps. These diffraction peaks are attributed to the diffraction of X-rays by the planes of atoms of much smaller separation than the basal planes, i.e. the lateral distance between one soap molecule and the next in a layer. The X-ray diffraction patterns of praseodymium soaps indicate that the long spacing peaks are fairly intense while the short spacing peaks are relatively weak.

Table: 3.2.1 X-ray analysis and determination of long spacings, d of praseodymium caprylate

S.N 2θ Sin θ λ/2 Sin θ d (Å) N

1 3.522 0.0307 25.091 25.10 1

2 7.261 0.0633 12.169 25.79 2

3 10.731 0.0935 8.239 25.50 3

4 14.339 0.1248 6.172 25.72 4

5 17.975 0.1562 4.931 25.06 5

6 21.357 0.1852 4.159 25.85 6

7 25.300 0.2189 3.519 25.96 7

8 28.996 0.2503 3.078 25.69 8

9 32.749 0.2819 2.733 25.83 9

10 36.511 0.3132 2.459 25.95 10 11 40.334 0.3447 2.235 25.87 11 12 44.190 0.3761 2.048 25.73 12 13 48.125 0.4077 1.889 25.91 13 Average value of d= 25.7Å

Figure: 3.2.1 Diffraction Patterns of Praseodymium caprylate 4 CONCLUSION

X-ray diffraction patterns of praseodymium soaps (praseodymium caprylate) show numerous peaks over the range of 3-80⁰ diffraction angles. The order of diffraction in these soaps decreases with the decrease in the chain-length of the praseodymium soaps. The values of average planer distance i.e. the long spacing for praseodymium caprylate, laurate, myrisate, palmitate and praseodymium stearte are somewhat samaller then the calculated dimensions of their corresponding anions i.e. caprylate, from Paulings values of atomic radii and bond angles. These values of long spacing increase with increasing chain- length of praseodymium soap.

The results suggest that the molecular axes of praseodymium soaps are somewhat inclined to the basal plane. The metal praseodymium fit into spaces between oxygen atoms of the ionized carboxyl group without giving a large strain of the bond. The difference in the long spacing of metal soaps approximately corresponds to double length of methylene

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ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING

Vol. 06, Special Issue 01, (IC-RCOVID19) April 2021 IMPACT FACTOR: 7.98 (INTERNATIONAL JOURNAL) 81 (-CH2) groups in the fatty acid radical constituent of the soap molecules. The zig-zag chains of fatty acids radicals extend in both directions with their axes somewhat inclined to the planes containing the metal ions. It is, therefore, concluded that praseodymium soaps are arranged in a parallel plane, i.e. a basal plane equally spaced in the soap crystal with fully extended zig-zag chains of fatty acid radicals on both directions of each basal plane and these soaps have double layer structure.

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