Aliphatic Halide-Carbonyl Condensations by Means of Sodium by Edgar A
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U . S. Department of Commerce Research Paper RPl909 National Bureau of Standards Volume 41, August 1948 Part of the Journal of Research of the National Burea u of Standards Aliphatic Halide-Carbonyl Condensations by Means of Sodium By Edgar A. Cadwallader, Abraham Fookson, Thomas W. Mears, and Frank 1. Howard As a part of an in vestigation of the synthesis of highly branched ali phatic hydrocarbons that is being conducted at the National Bureau of Standa rds for the National Advisory Committee for Aeronautics, the l\'avy Bureau of Aeronautics, and t he Army Air Forces, se veral compounds have been prepared by interaction of alkyl halid es a nd various carbonyl compo unds in the presence of sod ium. This reaction makes possible the sy nthesis of ce rtain highly branched compound s not easily obtain able by other m eans. L Introduction cooling of the reaction mixture was effected by application of hot or cold oil baths. In some The usc of the GrignaI'd reaction for synthesis cases, particularly with low-boiling solvents, both of highly branched compounds is limited by un small necks of the flask were fitted with reflux I desirable side reactions, which become progres condensers with the elimination of the thermom . sively more pronounced as the degree of branching eter. of the reactan ts is increased. These side reactions Sodium sand was prepared batch-wise by heat involve the l'eclu ction and enolization of the adduct ing a weighed amount of sodium in a purified ligh t rather than the desired addition of the alkyl group. mineral oil until melted, and then shaking the The recent work: of Bartlett and Schneider [1) 1 liquid sod ium vigorously in a closed E rlenm eyer and previous work by Morton and Stevens (13) fl ask until the des ired state of subdivision was ob indicate that the reaction between an alkyl halide tained. After the particles of sodium had cooled and an ester or ketone undel' the influence of sodium sufficiently, they were washed by decantation may be used to prepare certain compounds more with three or four portions of the solvent to be easily than by the GrignaI'd reaction, or may be used, transferred to the reaction vessel, and used in some cases in which the Grignard reaction immediately covered with solvent. fails completely as a synthetic tool. In this paper, A few of the first reactions tried in this series are described the )'Csults of a few reactions that were conducted in ?i-pentane (boiling range 34° to were designed to give information concerning the 38° C), but later ones were conducted in isooctane 2 scope of the reaction and the effect of variou s (boiling point, 99° C). It wa found that t he solvents an d temperatures of reaction . The work vigorous reactions were more easily con trolled of Bartlett and Schn eider has been extended to when the higher-boiling solvent was used. Also include a few additional reactants. the usc of isooctane as a solven t facilitated the use of higher temperatures for the reactions. II. Experimental Bartlett and Schneider carried out their reac tions by adding all of the alkyl halide to the sodium The apparatus u sed in making small-scale runs at once and then adding the carbonyl compound was the conventional three-neck flask of appro over a period of time. In attempting to usc this priate size, fitted with a stirrer, reflux condenser, and thermometer. A separatory funnel was 2 rrhis is the commonly used name for 2,2,4-Lrimcthylpentao (}, which is a placed at the top of the condenser. H eating and pri mary standard for octane number mea surements. rrhe commercially obtained material is exceptionally pure and se rves admirably as all inert I Figures in brackets indicate the literature references at Lbe end of this solvent for reactions of tbis type. Tbe co mmon nallle is used throughout paper. this paper. Aliphatic Condensations by Sodium III technique in our applications of the reaction, we were equipped with the type of distilling hear! often found that the reaction was so vigorous recently described [7]. that the sodium was completely consumed before Solvents used for t he Teactions were removed all of the carbonyl compound could be added. by distillation thTough these columns; the residues Apparently in these cases there is a self-sustaining were di stilled '(generally at reduced pTessures) in reaction between the sodium and the alkyl halide a Podbielniak H yper-cal column or in a Claisen that needs only a starting impetus given by the flask fitted with a short fraction ating column. carbonyl compound. In order to minimize this Yields were calculated on the basis of the eff ect only a small portion of the alkyl halide was amount of carbonyl compound that was added added at the start of the reaction, and the re to the reaction. Table 1 summarizes data ob mainder was mixed with the carbonyl compound tained on the sever al products, together with for gradual addition during the reaction. results reported in the literature. After the reaction had been carried to comple tion, the mixtuTe was decomposed eith er by pour 1. Diisopropyl Ketone and n-Propyl Chloride ing it into ice water or by direct addition of water Sodium sand (69 g , 3 g atoms) was added to 1 to the mixture in th e :flask. If any sodium was liter of isooctane in the reaction vessel. The visible in the flask, th e treatment with water was contents was heated to 80° C, and a solution of preceded by th e addition of small amounts of 114 g of diisopropyl ketone (1 mole) and 157 g of ethyl alcohol. After complete hydrolysis, th e two n-propyl chloride (2 moles) was gradually added. layers were separated and the organic layer After the reaction began, the temperature rose to washed with several portions of water. The or 95° C, which caused considerable re:fluxing. The ganic substance was finally dried over a suitable characteristic 3 greenish-black color appeared, drying agent. In those cases where the products and addition of the ketone-halide solution was of reaction were well known, only those physical continued at such a rate as to insure vigorous constants that were deemed necessary to identify re:fluxing. AdditiOll time was approximately 2 the product were determined. hours. After standing overnight the reaction Some of th ese reactions have been used for mixture was hydrolyzed, and the organic layer large-scale synthesis; the eq uipment used in these was washed and dTied. Isooctane and unre cases has been described previously [8]. acted n-propyl chloride were removed by distilla Methyl isobutyrate, t-butyl chloride, methyl tion , and the residue was distilled at reduced n-butyrate, isobutyl chloride, n-propyl chloride, pressure (Claisen flask). There was obtained and n-butylchloride were all made by standard 40 g of recovered diisopropyl ketone, an d 51 g of procedures. Ethyl trimethylacetate and hex a 2-methyl-3-isopropyl-3-hexanol (3 2% yield). This methylacetone (2,2,4,4-tetramethyl-3-pentanone) carbinol has been prepared by George [5] in 36- were prepared by methods previously described percent yield by the reaction of n-pl'opyl-mag [8]. Pentamethylacetone (2,2,4-trimethyl-3-pen nesium haJide and diisopropyl ketone. The resi tan one) was prepared by a large-scale run of the due (50 g) was a viscious material (boiling point reaction between ethyl trimethylaeetate and iso > 200 ° C, nn20 1.4590), and presumed to be a. propyl chloride by the method described herein. bimolecular product from condensation of diiso Pinacolone (3 ,3-dimethyl-2-butanone) [8] was pre propyl ketone. pared by the oxidation of 3,4,4-trimethyl-2-pen tene [8] with sulfuric acid-dichromate solution in a 2. Diisopropyl Ketone and Isobutyl Chloride manner analogous to that used previously for the A solution of 155 g of isobutyl chloride (1.68 preparation of 4,4-dimethyl-2-pentanone [8]. The moles) and 96 g of diisopropyl ketone (0.84 mole) other materials were ob tained commercially. was diluted with 200 ml of isooctane and added Only constant-boilillg materials that were col 3 'rhis reaction is visualized us starting with the formation of a sodium lected from distillation in a 180 by 2.5-cm Whit ketyl as the first step. 'rhis ketyl is colored all intense dark blue, blue-gl'crll. more and Lux [16] column were used in the purple, or black, depending, it seems, Oil one Or a combination of sP \'eral factors. It ha.c; bee n noted t h:lt in sc\'rra l reactions tripd, whero rraetion synthesis. Several of these columns were used ; failed to occur, n o chal'actcri:;t ic color was obscn ·cd. It is significant that some were packed with glass helices, the others this color appears fi rst on the surfa C4? 01 t he sodium. At this stasc, if or, ly a very small amo unt of ketone is prm~cn t in relation to t he amollnt DC halide', were packed with stainless steel helices, but all the co\oI' often oisappcal's as the ketonr I'racts. 112 Journal of Research TABLE 1. Reaction products Yleld pel I Refracti ve I I I _____~~ct i o_n____________ ~~o~=__ _____ ort ;~~~~ __~::~:: __ I_i_I_1(_le_X_' _"_10_ _r __D_ e~_, ~_,:t_.y_, _ Referen ce °C/mm H g 90 to 95/22 __________ _____ } ' 178 to 182/760 _______ ___ _ 1.