THE SOLUBILITY OF DOTRIAOONTANE AND TETRACOSANE IN CIS AND TRANS DECAHYDRONAPHTHALENE "by Sun Wing Tip A Thesis submitted in Partial Fulfilment of The Requirements for the Degree of MASTER OF APPLIED SCIENCE in the Department of CHEMISTRY The University of British Columbia April, 1941. ACKPTOWLEDGEMMT The writer wishes to express Ms appreciation and thanks to Dr. W. P. Seyer for his valuable and helpful suggestions given to him throughout this research. CONTENTS Page X xntro due t ion • &«««.•»•« *•»*•*••••«•• 1 II Materials used and Its Preparation »«»»»*»«•»»•» 4 2. • 0xs Decalxn «.«.«•«•.•••..••«...»•«»«»»..» 4 2• Dotrxacontane »•»».««•«.»«««»«*.«•«««««««. 5 3. Determination of Melting Point ........... 7 III Apparatus used and Experimental Procedure ...... 9 1« Capillary Method ............. 9 2* 33\il"b l^Eetlxod. 10 IV Resixlt s •«*••»•»*•«»••»*• «*«»«a»»»»oft»*ft»*& 12 ¥ Treatment of Results ................... • 17 71 Conclusion .............. 19 Sifrlio^rapii^r • «*•••• & «®*©6«©«*«*»«a&*»» SO j^ia^rams •«••*«••«• © • • *«• «.«*«&©•*» Melting Point Apparatus ..................... 7a Graphs 1. Weight percent Dicetyl vs. Temperature ... 2. Mol percent Dicetyl vs. Temperature ...... 3. Mol percent Dicetyl in various solvents vs« Temperature ...*«••.»*«•»............. 4. Log Mol fraction Dicetyl vs. Reciprocal of Temperature The Solubility of Dotriaoontane in Cis Decalin I Introduction A considerable amount of information regarding the mutual solubilities of hydrocarbons are available in the literature. About thirty years ago Holde found that light hydrocarbons when added to petroleum caused the asphalt • • 1 portion to be precipitated. In 1932 Pilat and Godlewicz g extended this idea and repeating the work of Kling treated a Polish petroleum with propane and precipitated most of the asphalt in the crude. The remainder of the asphalt was precipitated by using methane at a pressure of 30 atmospheres. This work established the fact that mutual solubility of hydrocarbons was governed largely by the molecular weights of solute and solvent. These facts are very valuable to the oil companies and already extensive use has been made by them in isolating and purifying certain petroleum fractions by utilizing solvents of various selective powers. In spite of all this information. , very little was still known of the quantitative, nature concerning the mutual solubilities of hydrocarbons* 3 In 1936 Dr. Seyer and Fordyce initiated the study of the systems of dicetyl and butane and dicetyl and propane to provide quantitative data on the mutual solubilities of hydrocarbons. They found that the mutual solubility : of hydrocarbons is a function of their molecular weights* Also from their curves of concentrations in mole percent against the freezing point temperatures they found that in the neighborhood of 55°G there is a change in the curvature of the curve. From this point downward solubility changes rapidly with the temperature, indicating the occurrence of two forms of dicetyl* Evidence for the existence of two forms of dicetyl was later found by measuring the refractive index at various temperatures below its melting point. The transition point is about 55°C. The following year Dr. Seyer4 extended this investigation by obtaining freezing point data of six separate systems of dicetyl with some low molecular weight hydrocarbons. The hydrocarbons used were as follows: dodecane, decane, octane, hexane, cyclohexane and benzene. From the curves of mole concentration against temperature for each system, there is a tendency for all the curves to coincide from the melting point of dicetyl on, until the concentration of this substance falls to about 40 mole percent, then the solute appears to exert its influence in determining the shape of the freezing point curve. These systems also showed no eutectic point or, if such a point exists, it would lie very close to the freezing point of the solvent. Since the study of decahydronaphthalene or decalin is of great theoretical interest mainly because of its two isomers trans and cis, it is intended to determine in this research the mutual solubility of dicetyl in cis decalin. The primary object is to find whether a saturated dicylic ring compound would have any serious affect on the solubility of dioetyl, secondly, to see whether or not a eutectic point is formed. Cis decalin was used because of its abnormal behavior as determined from the various physical properties such as viscosity, vapour pressure and refractive index measurements, whereas the trans decalin behaves quite regularly. Further it is hoped that the data obtained may 5 be used to check the equation of HiIdebrand . II Materials used and Its Preparation 1. Decalin The deoalin was brought from Eastman Kodak Company which was about 50 percent trans. The composition of the crude decalin is found to vary. These variations are probably due to variations in the hydrogenation process by which the decalin is manufactured. The cis decalin was separated from the trans by vacuum distillation at a pressure of 8 mm. of Hg. A charge of about 2000 cc. of the crude decalin was introduced in the still. The trans having a lower boiling point comes off in the first fractions. The refractive index of the various fractions were taken and those which contain high cis were mixed together and the whole rerun for pure cis. For further details and description of the distillation apparatus refer to the following theses: ' Kirk BASc Thesis 1935 Walker MASe Thesis 1937 Davenport MASc Thesis 1939 Then the high cis fractions are recrystallized for pure cis. This is done in a partially-evacuated double-wall glass flask, using a platinum resistance thermometer. By cooling a mixture high in cis, solid cis is formed leaving the mother liquid relatively higher in trans, this is of course assuming a binary system where there is a eutectic point. The liquid is poured off leaving pure cis with entrained trans. This procedure was repeated until the 5 temperature of cis formation remains constant for quite awhile. This temperature was considered as the freezing point of pure cis decalin. To avoid supercooling, the sample was innoculated with^frozen cis sample. The final freezing point of the cis decalin was taken as -43.22°C and was considered quite pure. 2. Dotriacontane or Dicetyl The normal straight chain hydrocarbon dicetyl used in this work was synthesized from cetyl iodide by the method 6 of Sorabji . The cetyl iodide was prepared from CP. cetyl 7 alcohol according to the procedure of Krafft in which hydrogen iodide.was passed repeatedly into melted cetyl alcohol. The hydrogen iodide was prepared by the action of water on phosphorous tri-iodide, the latter formed from white phosphorous and crystals of iodine. The hydrogen iodide gas liberated was passed through a red phosphorous absorption tower to remove as much free iodine as possible and finally into liquid cetyl alcohol until the latter was completely saturated. The cetyl iodide is formed according to the reaction c H + HI 0 H i6V i6W + 2° The cetyl alcohol was then purified to some extent by washing with distilled water repeatedly, using a fresh portion each time and separating after each washing in a separating funnel* The product was then reorystallized from ethyl alcohol removing the last traces of iodine. The cetyl iodide was then weighed and dissolved in ether and an excess amount of sodium^neeessary to remove the iodine was added. Since the procedure of Sorab-ji (loc. eit) was followed in this part of the synthesis, there is no need to repeat it here. The following reaction seems to take place: 2G16H33r -+ 23*a G32H66 + M The crude dicetyl was purified by repeated crystal• lization from glacial acetic acid, followed by reerystallization from ether. For the final purification only glacial acetic was used. The bulk of the acid was removed by siphoning and the rest by filtering the crystals and acid through a Buchner funnel using suction. To remove the last trace of acid, distilled water was run repeatedly through the dicetyl crystals using fresh portions each time; about 5 liters in all were used. This removed all the acid, as water and glacial acetic acid are exceedingly soluble. Then the dicetyl crystals were dried in a vacuum desiccator for a few days, after which a melting point determination was made. The recrystallization was repeated until a constant melting point was obtained. Fifteen recrystallizations were made after the second melting point determinations and no increase in melting point of the product was noted; The dicetyl was considered pure. 7 3» Determination of Melting Point The melting point of a solid substance which does not sublime or decompose on heating to its melting point is one of the best criteria of purity. Hence this method was used to determine the purity of the dicetyl. The procedure 8 used follows that of Piper , the apparatus consisting of a o. glass bulb witluside arm,holding about 150-200 cc. of concentrated sulphuric acid. It is fitted with a glass tube with a calibrated thermometer graduated in 0.1°C inside it. The diagram in the next page is perhaps self explanatory. The bulb is not stirred and by using a small flame and regulating the rate of heating, it is possible with care to repeat the melting points within an accuracy of 0.1°C. The temperature at which the substance shows the first sign of melting is taken as the melting point of the dicetyi. The final melting point of the dicetyl was 69.55°C as measured by the calibrated mercury thermometer, including stem correction. This agrees with that of Piper's (loc. cit) value 69.5°C to 69.7°C, yet differing from the value of other 9 investigators. Hildebrand and Wachter pointed out that the melting point of dicetyl should be approximately 70°c and they obtained a melting point of 70°C. If this is correct, then the dicetyl must have contained some of the next lower hydrocarbon* ie.