Dube, G P

Gupta, M P

English

IACS Institutional Repository

X -R A Y  CRYSTALLOGRAPHIC DATA ON RUBIDIUM  FU M A RA TE, MONOHYDRATE (Rbs, C* H  ^O4 , Hj O)M. P. GUPTA AND G. P. DUBED epautmknt of PiiYHU'S, Kajskjhi Colljcok, Ranchi (Jtecetved for puhhcation, Januaii/ 18, 1958)Plate TITABSTRACT. Singlo oiyHtal photof r^aiihs hIiow i-iibitlium futmiroio, monohydrato (Ubj CU Oj, H 2 O) to bo ti-ioliiiio wiUi,a =  9.23A, fa 7 51 A ,  (i 66 A a =  81 "5', p =  96'’42', y  ^  91°48''rimn' aro two formula units m  tho coll. 'J’ho .sj)aco grouji is suggostod to bo P  i .  Atl.ontion IS drawn 1-owards tho psoudo-inonoolinir symmotry Indoxed powor diffraotion data for tho ooinpouiid IS given, at tho end m tabular formSeveral potassium and rubidium salts ol funiaiie acid have been reported in Beilstein's Orp;aiiische Chcmic (Banrl 1 1 , Syst No 179, j). 637) and tbeir X-ray ( rystallograpbic examination was (;ompleted by Gujita (1953) and Gupta and Barnes (lOfiS). While the work on the determination of the crystal structure of ])otas- siLun fiiinarate, dihydratc (K, O4 O ,^ 2IT2 O) was 111 progress, the desirability of preparing an isomorphous iiibidiuni salt, rubidium fumarate, dibydrate (Rbg 112 O4, 2H 2 O) was felt. This compound is not reported anywhere in tho chemical literature but it was anticipated that by mixing stoichiometrio propor­tions of funiaric acid and rubidium carbonate, such a compouml could be pre- ))arcd Tn the event th a t the eoni])OLind so prepared did not turn out to be iso- iiiorphous with the corresjiondmg potassium fumarate, this result is being jiublishedPreparation • One gram of rubidium carbonate (Fischer, reagent) was mixed with the stoichiometric amounts of fumaric aind in water solution and the resulting solution was warmed, filtered off and left tor crystallization (by the method of slow evaporation) in crystallizing dishes. After a fortnight, several platy crystals were obtained with the (100) as the platy face. These were considered suitable for X-ray work after the usual examination ui the polarizing microscope.Unit cell : The unit coll which was found to be trichnic was determined by immnting a single crystal (1 mm X 1 mmxO.25 mm) on the Buerger precession ‘■ainera Tho reciprocal cell angles y*  and /f* wore measui’ed directly on the zero level procession photographs showing the reciprocal nets a*—h* and a*—c* respectively while the interaxial direct cell angle a,{b'~'c) was measured directly1 7133134 M , P . Gupta and G. P. Dubefroin the precession camera dial readings. These lead, using the formula for a triolinic cell, to the following values of the interaxial anglesa  =  8rr»', /? =  96°42', y =  91°48'The values of a*, h*, c* measured from zero level precession photographs showing the a*—b* net and a*—c* net and the above values of a, p  and y  lead to the fol­lowing values of the unit cell lengths :a ^  9.23 I ,  b =  7.51 A, : 6.56 Adooi — 6.54 A.Radiation used throughout Avas Mo A =  0.7107 A.. The reciprocal net a*~b*  shows a marked amount of inonoclinio pseudo-symmetry (Plate IIT).The density, measured by floatati<;n method using a mixture ox methyl iodide (density 2 279 gm/cc) and toluene (density 0.S67 gm/cc) was fouiid to be 2.23 gin/cc. Using the above values of the coll constants, the volume of the unit coll =  452.99 A*^ and the weight of the unit cell contents =  608.54 (atomic\units). Theoretical molecular weight for Rb.  ^ C4 Hg O4 is 284 88 (atomic units) I f  there are two such formula units per unit coll, the balance of 38.78 (atomic unit) can bo ascribed only to the presence of two water molecules m the unit cell (2x 18 — 36 atoniKi units). Thus the chemical formula of the compound was uniquely fixed as R b2C4 H 2O4, other possibility being consistent with the above dataSpace group : The diffraction symmetry observed is, of course, P I  > With the presence of two molecules per unit cell and in view of the pseudo-monocliinc symmetry th a t the crystal shows (figure. 1 ) the space grouji is suggested to be P i.The corresponding potassium salt of fumaric acid (Kg 4^ ^ 4) crystallizeswith two molecules of water of crystallization and is monoclmic, space group P2j/ .^. {Since the rubidium salt (Rbg C4 H 2 O4 ) crystallizes with only one mole­cule of water, this would explain th at the potassium and rubidium salts are not isomorphous, the rubidium salt crystallizing with lower triclinic symmetry, although psoudo-monoclmic symmetry persists. I t  may bo noted in passing that a similar lack of isomorphism exists in other corresponding rubidium and potas­sium salts of fumaric acid (Gupta, 1956).In  order to check whether a higher hydrated form of Rbg C4 H 2 O4 exists or not a powder photograph of Rbg C4H 2O4, HgO, sealed in arLindemann glass capillary tube was taken. One end of the capillary tube was then broken and this was made to touch a trace of water. By capillary action, the whole tube was then saturated with water. The resulting powder pattern of this water saturated sample did not show any changes from the corresponding powder photograph of RbaC4Ha04, Hg 0. Thus the possibility of a higher hydrated form of R b2C4 Ha O4 had to be ruled out.PTA & DUBEfncliari Jouinal of Phvhics, Vol. XX XIl, No. uPLATE JIJFig. 1. Zero level precession photograph ol rubidium fiiinarate, monohvdrate. I riclinir. a*—b* net with a* along the horizontal axis. —;^ o", F t) oo cni.s Mo Ko radiation, 0.7107 A. I he ])seudo-orlhogonalily ol thi net may be noiued d he loin .spots in the (eiitre making a square array an due to arndental leakage u( light in the f amera.a X-ray diHraction powder photograph of lubidmm lumarate, monohydrate. Camera 'araeter ■ 114 () mm ; radiation, Cu Kn.The powder photograph ot E-boC4H 204, H^O ih reprochiccd in figure 2, while the indexed powder data are given in Table T. The powder data (film method) were also checked by obtaining a diffraction curve from the Norelco Geiger counterX -R ay Crystallographic D ata on Rubidium, Fumarate, etc. 135TABLE IX-ray diffraction powder data (Indexed upto dn=£2A)d{A) d{A)Observed Calculated Ohservf d (^ il ciliated20 0.22 9.17 100 35 2 65 2 65 30 K2 64 11219 6.52 6 64 001 2.66 02212.67 22V29 5.06 5.63 10120 2 56 2 57 22i10 5 30 5 33 o nJO 5 04 5.05 101 12 2 53 2 54 311]2 53 20219 4 62 4 58 200 2.52 212]HO 4 39 4.39 111 8 2 49 2.47 030,2 48 221 150 3 98 3 97 201 2 49 1222 48 21225 3 09 3 71 02025 2 40 2.40 1.30]25 3 58 3 56 201 2.41 222Jno 3 45 3 45 1201 13 2 34 2 34 320]3 45 3 42021120j 2.34312 J35 2.31 2.32 131175 3 32 3.31 211] 2.31 212 J3 31 121J1225 2 27 2.25]5 3.24 3.27 00212 2.20 2 18 230]no 3.16 3.18 012] 2.21 4103.18 1021 2 20 0133.16 12lJ 2 19 0312 21 II.3J100 3.09 3 13 2ii8 2.16 2 16 230]no 3 02 3 03 021 2 17 103J36 2.89 2.90 2"20, 10 2.12 2.11 302'2.90 112] 2.13 0322 90 3011 2.12 1312.86 221-' 2 12 13235 2 11 4112.81 2.83 012] 2.13 322'2 84 1212.81 3102.81 2022.84 310.25 2.76 2.77 311]12.76 212J1136 M. P. Gupta and O. P. DuheTABLE I  {contd.)/M ld{A)hkl I I Id(A)O bserved CalculatedObsorvod Calculated10 2 0 8  2 .08 312 5 1 699 2,05  2 .06 203 7 1.6820 1,99 1.99 4X11 9 1.651.99 3 I 2 I 4 1 631 98 42111 99 2 2 2 J 3 1.604 1 95 3 J 584 1 90 3 1.5510 1 87 3 1.5210 1 855 1.81 3 1 503 1.78 4 1 .464 1.74 4 1 434 1.71hkldiffracitonieter capable of greater resolution. Tliei’e were good agreements re­garding the diffraction angles but not regarding the intensities for which the agree­ment witli him method was only (lualitativo. I'his may be due to preferred oricnla- tion of grams in the sample prepared for the Noroleo diffractometer and absorjitioiiA C K N O W J. JO n  G M JO N 'PThe experimental work was done during part of Exchange Visit Programnio P-72 a t the Polytechnic Institute of Brooklyn, N.Y , and one of us (Gujita) is greatly indebterl to Prof. 1. Fankucheu for providing all the laboratory facilitic'SK 10 K E R E N  C E SG upta, M. J’. 1953, P h . D, Thesis, U nivo isity  of London.G upta, M. P „  niid Baiiies, W  H  , 1958, Catutdinn Jonr)iairof Chemistry (m  iiross)G upta, M. P ., 1956, Acta Gryst, 9, 263.

X-Ray Crystallographic Data on Rubidium Fumarate, Monohydrate (Rb2 C4 H2 O4, H2 O)

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X-Ray Crystallographic Data on Rubidium Fumarate, Monohydrate (Rb2 C4 H2 O4, H2 O)

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