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The variation of solubility with structure in isomers Gill, Alan Findlay 1925

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5X5C32-?'fi^j.'£fe&d£iw;". .B.C. LIBRARY j •vs^wsw^^frfei**'1**^' *K£$2. n & . '*S^^r^«teS& !SKr^^sSi^eW3US<B^%v^c^ipr^^^^ "The \/fc-fr icsnEr\ of O 6']*^b i.Jvjy vvrf^ 0/7<^:fcv^il,> • ; ' ; . ; • : . . . , » Y AU-'F"^''1-% L£3'37 tx: A -f. fi THE VARIATION OF SOLUBILITY WITH STRUCTURE IN ISOMERS, by Alan Findlay Gill A Thesis submitted for the Degree of MASTER OF ARTS in the Department of CHEMISTRY THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1925 . f^2.H.a. THE VARIATION OF SOLUBILITY WITH STRUCTURE IN ISOMERS. The primary object of t h i s work was t o f ind the v a r i a t i o n i n the s o l u b i l i t i e s of t h e amylene isomers in l i q u i d sulphur d iox ide . From t h i s , i t was hoped some idea of the r e l a t i v e p o l a r i t y of the amylenes might be obta ined . This would give us a t e s t for our present method of deducing p o l a r i t y : i . e . from the conf igura t ion shown in t h e f ami l i a r s t a t i c formula. , For example, take the amylenes so f a r i nves t iga t ed ; oc-methyl-^ • e t h y l e thy lene , and t r i m e t h y l - e t h y l e n e . Their s t a t i c formulae are r e s p e c t i v e l y , H I E H H / / / / / H-C-C-C = C-C-H and / / / H H H From these formulae one would expect the latter to show the greater polarity, in so far as the molecule is more un-symmetrical. Indeed, Beilstein names the former "symmetrical" methyl-et hyl-ethylene. Now the relative polarities of isomeric molecules can be gauged in three ways: {1) readiness with which they polymerixe, (2) attraction for another polar molecule, leading to miscibi-lity, (the more polar compound would be the more miscible H / H-C-H \ 0 / H-C-H / H H / - 0 \ HC-H / H * * £ _ « » with the third compound), (3) according to Maass, by the re-lative magnitudes of the melting points; the higher melting point denotes the greater attraction of the molecule for its own species. A second reason for undertaking this work was to test the statement that olefines and sulphur dioxide are miscible in all proportions. It was claimed by Messrs Moore, Morrell and 2 Bgloff that naphthenes, paraffines and olefinic hydrocarbons oould be separated by this means. It has been shown that 3 4. 5 cyelohexane, normal hexane and oetene-' have limited solubi-lities in sulphur dioxide. An examination of a lower define-araylene-would complete the series and prove or disprove this statement for the lower homologues. Thirdly, it was desired to observe the systems sulphur dioxide-amylene for evidence of molecular compound formation^ Any results obtained here would give a clue to the mechanism of compound formation observed by other investigators. The cc-methyl-3-ethyl-ethylene was synthesized from propyl alcohol. To convert the propyl alcohol to propional-dehyde oxidation by chemical means was first tried. The method 1. Jour. Frank. Inst. 1924. 2. Met. and Ghem. Eng. Ho. 8-1918. 3. Seyer and Dunbar, Jour. Roy. Soc. Oan. 1922. 4. Seyer and Gill, Jour. Roy. Soc. Oan. 1924. 5. Seyer and Huggett, Jour. Roy. Soc. Can. 192 4. - 3 -was found to be unsatisfactory because the product could not 6 be readily purified. Catalytic oxidation was then employed. The alcohol wa8 passed over finely divided copper at 230-240 deg. The catalyst was prepared by passing dry hydrogen over a mixture of oxidized copper gauze and finely divided copper oxide at 300 deg. The alcohol was introduced through a fine capillary from a vertical tube. By regulating the height of h=,a xl alcohol in the tube the rate ' of entry could be controlled. - rpjle pro^Q-^ a mixture of 1 hydrogen gas, propyl alcohol and propionaldehyde was pas-sed through a long condenser and the alcohol and aldehyde obtained. By careful fractiona-tion the aldehyde was obtained pure from the alcohol solution. This method gave a yield of only thirty per cent, but it could doubtless be improved by the use off a vertical furnace. The boiling point of the aldehyde was found to be 49.8 deg. at 739 mm. It was dried with calcium chloride and distilled. Ethyl bromide was then prepared and the magnesium addi-tion compound formed* This was allowed to react with the aldehyde in ethereal solution. On splitting off the addition product diethyl oarbinol was obtained from the ether solution. 6. Sabatier and Senderens, A. Oh. (8) 4-462. - 4 -This again was obtained by fractionation, there being a large difference in the boiling points. The yield was 85 to 90 per cent. After drying with fused potassium carbonate the alcohol waa distilled. The boiling point was 114.2 - 115.2 deg.; the density 0.8341 (Do) (C.F. 0.8315, Wagner, Saizew; 0.8381, Grignard). The alcohol was converted to iodide with red phosphorus and iodine. The amyl iodide was not distillable at ordinary pressure and decomposed on standing. On treatment with alcoholic potash it gave the amylene. The yield of impure product was about eighty per cent. This was washed with water and sodium carbonate, dried with fused potassium oarbonate and distilled.' The above synthesis may be represented graphically as follows: (1) CHj CH2 CH2OH OHj 0H2 C^H+H2 (2) OEj CH2 MgBr+CH3 CHgC H CH^ 0Hg-<<? s CH^ 0H2 (3) CH* CH* .OIL-Br GHz CH2 c' 5 + H20 >^CHOH-t-MgBrOH. OHj OH^^H CHj GH 2 (4) OH* 0HPx CH, 0H9 3 P ^.OHOH + PI* 3 OHj CH2/ OHj 0H2 (5) 0H3 OH2. GH3 GH2 >HI+. KOH % ' >H^EItH 20 CH3 CH2/ (Aleoh.) OH5 OH^ ~» p m The t r ime thy l - e thy lene was obtained from G. A. F . Kahlbaum Go. Both of these hydrooarbons, a f t e r p u r i f i c a t i o n , were d i s t i l l e d over sodium. I t i s i n t e r e s t i n g t o note t h a t the former did not polymerize to any appreciable ex ten t , while the l a t t e r polymerized f a i r l y r ap id ly t o a substance having a t e rpene~l ike odor. Some phys ica l p r o p e r t i e s off the two isomers are given in Table I . TABLE I . cc--Methyl-J3 - e t h y l - e t h y l e n e Trimethyl-ethylene observed Be i l sxe in observed B e i l s t e i n Boi l ing Pt.-56.5-57(754mm) 56(740mm) 58(762mm) 58 Melting Pt— -*149.5 -146.1 Density U>4°}.6545 ( D | ° ) . 6 5 9 5 (D°}.6785 ; > (D^) .6678 Mol. Ref,(Md) 24.80 (ca lc :24 .75) 24.89 (ca lc :24 .75) Mol. Disp. 0.579 ( c a l c : . 4 9 5 ) .478 (MD-Ma) In determining the s o l u b i l i t i e s of t h e amylenes in l i q u i d sulphur dioxide the bulb method was employed. As there i s r e a c t i o n in presence of moist a i r t p recaut ions were taken to exclude a i r from t h e bu lbs . This was very d i f f i c u l t . A method was attempted whereby sulphur dioxide gas in severa l r e s e r v o i r s of about two l i t r e s capaci ty was condensed in t he bu lb , the amylene being d i s t i l l e d in from a c a l i b r a t e d t ube . J* - 6 -The differences in pressure of the sulphur dioxide were read with the cathetometer on a mercury manometer. Owing perhaps to the presence of minute traces of air this method was found to be extremely slow. Also the apparatus was very sensitive to room temperature. The apparatus finally used is shown in figure II. f. O iW^, "*vr i\ u. p V -——iky — ^ 6 4 A and B were graduated and calibrated with mercury. Dry sulphur dioxide was con-densed in A under pressure through the stop cock (I). Amylene was drawn up into B, The connecting tubing and bulb were then evacuated and the required amounts of amy-lene and sulphur dioxide were distilled into C. The differen-ces in height in their respective tubes were read, after room temperature had been attained, with the cathetometer and the weights of amylene and sulphur dioxide calculated. When the bulbs had been filled they were sealed off. Both the amylenes were found to be miscible in all pro-portions in the liquid phase with sulphur dioxide. According-ly, to obtain their relative solubility, their freezing point curves were determined. They are shown in figure III. The higher points were determined in a carbon dioxide-- 7 ether bath. The lower ones were taken in a petrol ether liquid air mixture. Owing to the fact that petrol ether freezes between -140° and -1^0°, the lowest points had to be taken by a speoial method. The degree of super oooling was about twenty-five degrees so the bulbs were frozen initially in liquid air. Some of the points were very diffioult to obtain, the mixtures forming a "glass" instead of crystals. The bulbs oould not be opened to stir their contents so the freezing points had to be tgken approximately: they are correct to within three degrees. It is interesting to note that the mixtures had the properties of glass and cracked in a manner similar to glass on rapid cooling in liquid air. Symmetrical methyl-ethyl-ethylene crystallized very well and its freezing point was determined from the bulb. Trimethyl-ethylene was more difficult to crystallize. A small flask of it with a stirrer and a resistance thermometer in the liquid Has lowered into liquid air. By rapid stirring cry-stallization was started. When the mass was frozen the flask was raised slightly above the liquid air and the temperature was allowed to rise slowly. A series of readings were taken on the resistance thermometer at intervals of one minute. The point at which the resistance stayed constant for six or seven minutes was taken as the freezing point. By using the amylene as a bath, other low freezing mixtures were deter-mined. All temperatures were determined with a standard - a -resistance thermometer. In getting the melting points of the crystalline mixtures the temperature was slowly raised until there was equilibrium between a very little crystal and the liquid. This point was taken as the freezing point. When the freezing points had been determined the percen-tages were checked by weighing the bulbs, cooling and opening them and inverting them in standard alkali. The excess alka-li was titrated with standard hydrochloric acid. This gave the weight of sulphur dioxide. The percentage was determined by weighing the empty bulb. Table II gives the percentages. TABLE II. " ocmethyl-:ff -ethyl-ethylene Trimethyl-ethylene * Percent SOg Freezing Point. Percent S02 Freezing Pt. 0 1.3 16.1 30.1 40.3 63.4 76.8 80.9 93.6 -149.3 -w;# -130.4 - 89.0 - 85.6 - 79.0 - 77.8 - 77.9 - 73.2 # Approximate, 0 3 13.5 29.1 49.9 65.6 79.7 90.2 100. -146.1 -154.# -l60.# -143.2 - 91.6 - 82.5 - 80.8 - 77.1 - 72.9 It has already been observed that trimethyl-ethylene - 9 -shows a greater tendenoy towards polymerization. A compari-son of the freezing-point curves (fig.Ill) shows that it also has greater solubility in liquid sulphur dioxide. It also has a slightly higher melting point. For these three reasons then, it might be said to show greater polarity than -methyl--ethyl-ethylene. If we take an increase of density ( the molecular weight being constant) to mean increased attraction with consequent drawing together of the molecules, we have additional evidence. At this point something might be said with regard to Maass1 theory of polarity. He suggests that the higher the melting point the greater is the attraction of a molecule for its own species. For isomers this seems to hold good, but is is contrary to the behaviour of homologous series, the lower members of which are more active in every way and alone show a tendency to polymerize. It is more reasonable to assume that the molecular weight plays a part in the polarity, the hydrocarbon with the higher molecular weight being less polar. The polarity might be expressed by „ P = f (4) where T is the melting point and M the molecular weight. He also states that the attraction of a molecule for one of a different species varies inversely as the melting point, the assumption being that as one attraction diminishes the other comes into play. Now, if it be granted that the molecule as a whole is electrically neutral, then polarity must be •in h>u ) "£>(C>i v ^ / O ^ IT oejin(---v j u a a / s ; 'P C-G 0 8 oz 09 Off 0 + o r 0 2 01-..!.. 4?9-'sr^Aj^iQ -j-^iioj_ bui-zs>--jJ^ - 10 -caused by distortion of the electric field due to the unsym-metrioal nature of the particular molecule. Consequently a molecule will not exercise selectivity in its attraction, although its attraction for different molecules may vary. Moreover, if the melting point is lower, the polarity is less, and consequently the molecule would have decreased attraction not only for itself but for other molecules as well. This would lead one to believe that the compounds he obtained were the result of chemical action, however slight. The second object oif this work has been fulfilled. The amylenes and sulphur dioxide are miscible in all proportions. This showa that the statement that olefines and sulphur dio-xide are miscible in all proportions is true for the lower members of the series, although no practical use could be made of this in oil refining. There is no evidence of compound formation in the curves. Compound formation is shown in a two component system by the presence of more than one euteotic. While at present it so happens that there is a fairly large break in temperature in the two curves, a calculation shows that any compound would occur at about fifty per cent concentration. The curves cover this region satisfactorily. One conclusion may be drawn from the faot that no com* pounds are found. In short: molecular compounds obtained under these conditions are chemical and not physical. To - 11 -oonsider this let us look at compounds obtained by other in-vestigators. Halogen hydrides and certain non metallic oxides were investigated by Bruner and Wroozynski'. At the temperature of liquid air they found changes in color and formation of various solids, The system S02-N0 gave a pale green sub-stance which on addition of water yielded sulphuric aoid. This looks like a simple oxidation and reduction reaction. The system SOg-HOI gave an orange yellow substanoe - "Pro-bably an addition compoundw, p Korezynski and Glebocka worked on sulphur dioxide and various amines. At room temperature and at zero degrees they found changes in color of the liquids; nearly all became a canary yellow shade. They analysed for the uncombined sul-phur dioxide and assigned empirical formulae to these. Now aside from the fact that nitrogen in an amine is trivalent and can readily become pentavalent (e.g. aniline hydrochlo-ride), too much stress can be laid on the color changes. Both hexane and amylene solutions in sulphur dioxide have been observed to be colored yellow in certain proportions. This color is sometimes quite pronounced, at other times there is none at all. That no action took place is proven by the solubility curves. 7) Z. An, Ghem. (63) - 49. 8) Gazs. Chem. Ital. 50, 1, 278 - 87 (1920). [ - 12 -Lastly in Maass* work, he used halogen hydrides and aromatic or halogen hydrides and unsaturated aliphatic hydro-carbons. He kept his systems below -100° and determined freezing point curves. While he states that no chemical re-action took place at the low temperature a chemical explana-tion would seem to be the best, i.e. that HBr added on to the double bond as it does under ordinary conditions. . The results with amylene and sulphur dioxide bear out this supposition. One oan hardly conceive of sulphur dioxide and amylene reacting chemically, but both molecules have con-siderable polarity. Consequently, any compound obtained be-tween them would be due to their polarity and not to chemical action. That there is no compound supports but does not prove the suggestion that addition compounds are of chemical formation. In conclusion I wish to thank Dr. Seyer for his valued assistance and advice in carrying out this work. BIBLIOGRAPHY. E. Briner and A. Wroczynski.Uber die Chemische Wirkung eines hohen Druokes auf die Gasmischungen- .Zeitschrift fur Anorganische Chemie 63 - p. 49. A. Korezynski and M. Glebooka - Molecular Compounds of Sulphurous Anlydride with the Amines. Gazz. Chim. ital. 50, I. p. 378-87 (1920). 0. Haass - Molecular Attraction and Molecular Combination. Journal of the Franklin Institute, Vol. 158, No. 2, p. 145, August 192 4. R. J. Moore, J. C. Morrell and G, Egloff. The Solubility of Paraffins, Aromatios, Naphthenes and Olefins in Liquid Sulphur Dioxide, Metallurgical and Chemical Engineering No. 8 -1918, p. 396. P. Sabatier and J.-B. Senderens. Nouvelles Methodes generales d'Hydrogenation?Annales de Chimie et de Physique. Serie 8 - Tomme 4 - 1905, p. 4-62. W. F. Seyer and Y. Dunbar. The Solubility of Cyclohexane in Liquid Sulphur Dioxide. Transactions of the Royal Society of Canada. Third series - 192£; Vol. XVI, p. 307. W. F. Seyer and A. F. Gill. The Mutual Solubility of Sulphur Dioxide and Normal Hexane. Transactions of the Royal Society of Canada. Third series 1924; Vol. XVIII, p. 209. W. F. Seyer and J. L. Huggett. The Mutual Solubility of Cetene (Hexadeoene) and Liquid Sulphur Dioxide. Transactions of the Royal Society of Canada. Third series 1924; Vol.XVIII,p.213. 


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