Home > Journals > Canadian Journal of Chemistry > List of Issues > Volume 31, Number 5, May 1953 > REFRACTIVE INDICES OF SOME SATURATED AND MONOETHENOID FATTY ACIDS AND ...
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`REFRACTIVE INDICES OF SOME
`SATURATED AND MONOETHENOID
`FATTY ACIDS AND METHYL ESTERS
`B. M. Craig
`
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`Citing articles
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`Canadian Journal of Chemistry, 1953, 31(5): 499-504, https://doi.org/10.1139/v53-068
`
`ABSTRACT
`The refractive indices for a number of saturated and monoethenoid fatty acids and their
`corresponding methyl esters have been determined. Equations have been calculated to obtain the
`refractive index at any given temperature. Significant differences have been found for the
`temperature coefficients of refractive index within an homologous series and between the free fatty
`acid and the corresponding methyl ester.
`
`Cited by
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`OZONOLYSIS OF UNSATURATED FATTY ACIDS: I. OZONOLYSIS OF
`OLEIC ACID
`
`R. G. Ackman, M. E. Retson, L. R. Gallay, F. A. Vandenheuvel
`
`Canadian Journal of Chemistry, 1961, 39(10): 1956-
`1963, https://doi.org/10.1139/v61-262
`
`» Abstract
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`

`REFRACTIVE INDICES OF SOME SATURATED AND
`MONOETHENOID FATTY ACIDS AND METHYL ESTERS1
`
`ABSTRACT
`The refractive indices for a number of saturated and rnonoethenoid fatty
`acids and their corresponding ~nethyl esters have been determined. Eq~wtions
`have been calculated t o obtain the refractive index a t any given temperature.
`Significant differences have been found for the temperature coefficients of
`refractive index within an hotnologous series and between the free fatty acid
`and the corresponding methyl ester.
`
`The literature contains few references to systematic studies on the refractive
`indices of the fatty acids and their esters, particularly the variation in refrac-
`tive index with temperature. Dorinson, McCorltle, and Ralston (1) have
`reported refractive indices for the saturated fatty acids from caproic to
`stearic a t five degree intervals of temperature. Wyman and Barltenbus (8)
`determined the refractive indices of the methyl esters of this series of fatty
`acids a t 45OC. and this work was extended by Mattil and Longenecker (5)
`who determined the variation in refractive index as a function of temperature.
`The latter workers computed equations to calculate the refractive indices a t
`any intermediate temperatures. More recently Krewson (3) has p~iblished
`data on the refractive indices of the methyl esters of the saturated acids up to
`and including methyl octacosanoate a t temperatures of 50°C. and 80°C.
`Data on refractive indices of unsaturated acids and esters are inore meager
`than for the corresponding saturated series. Wood et al. (7) have reported
`on the refractive indices of oleic, elaidic, linoleic, and linolenic acids a t 50°C.
`McCutcheon (4) determined the refractive indices of ethyl linoleate and eth5.l
`linolenate over the range 20°C. to GO°C.
`In the course of some work on rapeseed oil the saturated and monoethenoid
`acids and esters of the CI6 to Czz series were purified, and a refractive index
`study was made on these materials. Equations were calculated from the data
`expressing the refractive index as a function of temperature.
`
`MATERIALS AND METHODS
`Crude commercial stearic acid was used as a source for ~nethyl palmitate
`and methyl stearate. The crude acid was hydrogenated to a negligible iodine
`value and converted to methyl esters by conventional procedures. The crude
`esters were distilled in a Podbielniak "Heli-Grid" distillation colu~nn. The
`methyl palinitate and methyl stearate fractions were redistilled and fraction-
`ally crj,stallized to yield piire esters. Methyl oleate was obtained by converting
`olive oil to the methyl esters and distilling the esters. The Cl* fraction was
`repeatedly crystallized from acetone until the precipitates and filtrates
`agreed in refractive index. The purified methyl oleate was then redistilled in
`
`fiIanu,cripl received Jnnztary SO, 1.955.
`Contribz~tion from the Prairie Regional Laborafory, Division of Applied Biology, i\'ational
`Researclt Council, Saskatoon, Sask. Isszred as N.R.C. No. 1961.
`ilssistant Research Ojiccr.
`?
`
`490
`
`Reactive Surfaces Ltd. LLP
`Ex. 1047 (Ray Attachment M)
`Reactive Surfaces Ltd. LLP v. Toyota Motor Corp.
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`Can. J. Chem. Downloaded from www.nrcresearchpress.com by 159.87.53.104 on 10/27/17
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`

`

`500
`
`C A N A D I A N JOLJK.V;l L O F CNEMISY'KY.
`
`irOL. jl
`
`the Podbielnial; column.. Methyl eicosenoate and methyl erucate \\:ere pre-
`pared fi-on1 rapeseed oil in the same manner. Methyl belienate and methyl
`arachidate were prepared from the corresponding monoetlienoid esters by
`hydrogenation with Raney nickel followed by fractional crystallization.
`The pure fatty acids were obtained by saponification of the corresponding
`pure methyl esters and fractional crystallization. The physical and clielnical
`constants of the esters and acids are given in Table I. Iodine values were
`
`T A B L E I
`PHYSICAL
`A N D CIlEhlICAL CONSTANTS FOR FATTY ACIDS A N D blliTHYI. 1,:STEKS
`I
`
`I
`
`- - - .. -. --
`
`1
`
`. .
`Eicosenoic
`Erucic
`Palrnitic
`Stearic
`
`Behenic
`
`Acids
`
`T:y. 1 M.P.
`
`I.V.
`- -
`
`81.62
`74.81
`
`0
`
`
`
`1 M.P.
`
`Reported
`
`I
`
`I
`'1
`
`1
`
`Esters
`
`I.V.
`
`Theor.
`I.V.
`
`Reported
`M.P.
`
`determined by the Wijs method, one hour reaction time and 0.1 N solution.
`i\iIelting points were measured by the \i17iley method using a Bureau of
`Standards thermometer and applying stem emergence corrections. Diene and
`triene acid contents of tlie unsaturated esters and acids were determined
`according to the standard A.O.C.S. procedure. No measurable quantities were
`found in any of the monoethenoid esters or acids.
`A Bausch and Loiiib Abbe type refractometer equipped with a circulating
`water bath controlled to f 0.005°C. was used to measure the refractive
`indices. A thermometer calibrated against a Bureau of Standards thermometer
`\\;as used to read the temperature in the prisin and stem emergent corrections
`were applied to the therniometer reading. No prism corrections were applied
`to the refractive index values. The refractive indices were measured a t five
`degree intervals over the temperature range a t which tlie material under
`study was in the liquid state from 20°C. to 85OC. The refractometer was
`carefully calibrated with the test piece supplied by tlie manufacturer and
`clieclted with purified ethyl oxalate and ethyl citrate.
`
`R E S U L T S
`Equations for calculation of refractive indices of the esters and acids a t
`any given temperatures are listed in-Table 11. The equations were calculated
`by the method of least squares and the error of estimate for the equation and
`the standard error of the regression coefficient are included. The errors of
`estimate of the equations listed in Table I1 are of the same order as the error
`of meas~lremeiit of refractive index credited to tlie instrument used in the
`
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`

`C R A I G : REFRACTII'E IlVDICES
`
`- -- - - - - -. -- -. - - -
`
`- -- - -- - - . . -.
`
`Standard
`error of
`estimate
`-- -. - -
`
`Stanclarti
`error oi
`regress~o~l
`coetficie~~t
`
`1Z.I.t = 1.45968 - 0.000377t
`Methyl oleate
`
`Methyl eicose~~oate li.1.t = 1.46131 - 0.000372t
`Methylerucate
`R.I.t=1.46288-0.000369t
`Methyl palmitate K.1.t = 1.14830 - 0.000379t
`R.1.t = 1.15149 - 0.000375t
`Methyl stearate
`Methyl arachidate R.1.t = 1.15363 - 0.000366t
`Methyl behenate R.1.t = 1.45551 - 0.000358t
`Oieic acid
`R.1.t = 1.46677 - 0.000354t
`Eicosenoic acid
`R.1 .t = 1.46805 - 0.000351 t
`R.1.t = 1.46892 - 0.000346t
`Erucic acid
`Palmitic acid
`R.1.t = 1.45559 - 0.000355t
`
`K.Z. t = Refrnctive ixden nt te~nperatzire t'C.
`
`I
`
`I
`
`@ E R U C l C ACID
`@ EICOSENOIC ACID
`@ OLElC AClD
`@ ARACHlDlC AClD
`@ STEARIC AClD
`8 PALMITIC AClD
`
`I
`20
`
`1
`4 0
`
`I
`6 0
`
`I
`80
`
`\ j
`
`TEMPERATURE
`'C
`FIG. 1. Refractive indices of fatty acids a t different ten~peratures.
`
`study-. Lines representing the equations and the experimental values for
`refractive indices are presented graphically in Figs. 1 and 2.
`
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`

`C A N A D I A N J O U R N A L O F CHEBIISI'KY. V O L . 31
`
`O M E ERUGATE
`@ M E EIGOSENOATE
`8 ME OLEATE
`@ME BEMNATE
`@ M E ARAGHIDATE
`@ M E STEARATE
`@ME PALMITATE
`
`I
`
`I
`20
`
`I
`4 0
`
`1
`6 0
`
`I
`8 0
`
`TEMPERATURE
`
`.G
`
`\
`
`FIG. 2. Refractive indices of methyl esters of f a t t y acids a t different temperatures.
`
`Table I11 shows a co~llparison of the values obtained experimentally and
`those calculated from the equations given in Table 11. Experimental values
`are included for stearic, arachidic, and behenic acids where there were in-
`sufficient data to calculate the necessary equations.
`The refractive indices for acids and esters given in this study agree quite
`well with those reported by other worlters. The equations which are given
`in Table I1 represent an accurate and convenient ineans for calculating
`refractive indices a t any temperature and are a definite advantage where
`temperatures other than those reported in the literature are used to measure
`refractive index. I t is interesting to note that the temperature coefficients of
`refractive index given in the equations in Table I1 vary in a regular manner
`within an homologo~~s series of acids or esters. Statistically the difference rnay
`not be significant between any two consecutive members of the series, e.g.
`methyl palmitate (0.000379) and methyl stearate (0.000375), but the difference
`is significant between two members such as methyl palnlitate (0.000379) and
`~nethyl behenate (0.000358). I t must also be noted that there are significant
`differences between the temperature coefficients of refractive index for the
`methyl esters and the corresponding free fatty acids. The practice of using the
`general figure 0.00038 as the temperature coefficient of refractive index will
`lead to an error, the magnitude of which will depend on the temperature being
`used.
`
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`

`

`CRAIG: REFRBCTII,'E INDICES
`
`503
`
`TABLE 111
`CONPARISON OF CALCULATED AND EXPERIMENTAL REFRACTIVE INDICES
`
`--
`
`I
`
`Experimental
`----
`
`Calculated
`
`IS
`'ID
`
`Methyl oleate
`Methyl eicoserioate
`Methyl erucate
`
`Methyl palmitate
`Methyl stearate
`Methyl arachidate
`Methyl behenate
`
`Oleic acid
`Eicosenoic acid
`Erucic acid
`
`Palmitic acid
`
`Stearic acid
`Xrachidic acid
`Behenic acid
`
`I
`
`I
`
`1 ,42545
`
`1 42550
`
`Experimental refractive indices
`
`The differences in the coefficient for the monoethenoid methyl ester and the
`corresponding saturated methyl esters; e.g. methyl oleate (0.000377), methyl
`stearate (0.000375), do not seem to be statistically significant. However
`reasoning in the sanle manner as for the l~on~ologous series given above, the
`difference might be shown to be significant if this study were extended to
`i~lclude diethenoid and triethenoid acids and esters of the same chain lengths.
`
`REFERENCES
`1. DORINSON, A., MCCORKLE, M. R., and RALSTON, A. W. J. Am. Chem. Soc. 64: 2739.
`1942.
`2. FRANCIS, F . and PIPER, S. H. J. Am. Chem. Soc. 61: 577. 1939.
`3. ICREWSON, C. F. J. Am. Chem. Soc. 73: 1365. 1951.
`
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`
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`

`50.4
`
`C.AN..IDIA.?; JOURNAL OF CIIEIIfISTRY. 1'OL. 31
`
`J. W. Call. J . Research, B, 16: 168. 1938 and B, 1s: 231. 1940.
`MCCUTCIIEON,
`MATTIL, I<. F. and LONGENECKPR, H. E. Oil & Soap, 21: 16. 1944.
`RALSTON, A. W. Fatty acids and their derivatives. John Wilcy cfc Sons, Inc., N e \ v Yorl;.
`-- -".
`194x
`I-I. E. J . .AIII. Chem.
`
`7. WOOD, T. R., JACKSON, F. L., BALDWIN, .%. R., and LONGENECKEK,
`Soc. 66: 287. 1944.
`F . Mr. and BARKENBUS, G. Ind. Eng. Chem., -411al. Ed. 12: 658. 1940.
`S. \ \ r ~ ~ f i ~ ~ ,
`
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