Thii lead- to the equal ion cos2(a - PO) = 1 and corresponds to the maximum value for Rc,450.Thus with a knowledge of CY, the value of R,,450gives direct acce-s to the difference tR - I,) or ( k , kl)-\iz.,
R -L
=
x
(k,
- kJlc
=
LITERATURE CITED
(1) Carroll, B., Blei, I., Sczence 142, 200 (1963). (2) Crumpler, T. B., Ilyre, W. H., Spell, A , , ASAI,. CHEM.27, 1645 (1955). (3) Djeragsi, C., “Optical Rotatory Dispersion, McGraw-Hill, New York, 1960. (4) Heller, IV., in “Technique of Organic Chemistry,” A. Weissberger, ed., 3rd ed., Vol. I, Part 111, Chap. 33, Interscience, New York, 1960.
(5) liouy, A. L., U. S. Patents 2,993,404; 3,001,439. (6) Rouy. A. L., Carroll, B., AKA],. CHEV.33. 594 11961). ( 7 ) Rouy, A . L.; Carroll, B., Quigley, T. J., Ibid., 35, 627 (1963). (8) LVoldbye, F., Bagger, S., private communication, Uppsala Cniversity, Sweden, 1962. RECEIVEDfor review June 12, 1964. Accepted October 5, 1964. Work supported by the Corn Industries Research Foundation.
Quantitative Determination of Ozonides by Trip henylp hosphine OTTO LORENZ’ Research Division, Th’e Goodyear Tire & Rubber Co., Akron, Ohio
b A method for the quantitative determination of ozonides i s based on their reduction to the corresponding carbonyl compounds with an excess of triphenylphosphine cind subsequent titration of the unreacted triphenylphosphine with iodine. The reaction i s carried out in an alcohol solution for three days at room lemperature in the absence of oxygen, Ozonides have previously been determined iodometrically and while this method i s satisfactory for ozonides that form ketones on reduction, ozonides that form aldehydes on reduction give low results. The method with triphenylphosphine proceeds quantitatively when aldehydes as well as ketones are formed. A number of relatively pure ozonides have been prepared and analyzed by the proposed method.
Q
UAKTITATI1‘E
DETERMINATIOX
Of
peroxides by the oxidation of iodide ions to iodine is a well established analytical inethod ( 6 ) . Ozonides, likewise, will oxidize iodide ions quantitativelj-, but only if the ozonides yield ketones upon reducti’on. With ozonides that form aldehydes, low values are obtained, the results being as low as 60y0 of the theoretical value ( 2 ) . -in investigation of the reduction of ozonide:: with triphenylphosphine indicated that this reaction also proceeds quantitatively when aldehydes are formed on reduction. Challenger and Wilson ( I ) observed in 1927 that benzoyl peroxide rea,cts with triphenyl1)hosl)hine with the formation of benzoic anhydride. This reaction proceeds quantitatively as found later by Horner and Jurgcleit ( 3 ) . These authors also
included dimethylbutadienebulfone ozonide in their study and obsei\ed that diacetylsulfone wa< formed upon reduction with triphenylphosphine. EXPERIMENTAL
Reagents. Aqueous iodine solution, 0.1s. Triphenylphosphine (Eastman) 97.57, purity. Solvents. The solvents were reagent grade or purified by di-tillation. The phenols were commercial materials. Ozonides ( 4 ) . Ozonides were prepared by ozonization of the corre-
Table I.
Determination of Ozonides by Reduction with Triphenylphosphine
Ozonide 2-Biitene ozonide 2-Hexene ozonide 3-Hexene ozonide 4-hlethyl-2-pen tene ozonide 3-Heptene ozonide 1,2-Dimethyl-cyclopentene ozonide 4-Octene ozonide 2,5-Dirnethyl-3hexene ozonide 4-Nonene ozonide 2,6-l)iniethy1-3heptene ozonide a
I,
Present address, Kiilnisrhe Gnmiiif#den-Fabrik, Cologne, Germany.
sponding olefins a t -78’ C. using a dry ice-acetone cooling mixture. The ozone was produced with a Welsbach 1’-23 laboratory ozonator using d r y oxygen. No explosions were encountered if the ozonization was carried out in a suitable solvent such as n-pentane, a t a low temperature, and in the absence of moisture. The monomeric ozonide was separated from the total ozonization product, which usually contained many polymeric products, by distillation under reduced pressure a t temperatures preferably under 60” to 70” C. The distilled product was further purified by dis-
Ozonide taken, mniole 0 274 0 547 0 305 0 611 0 348 0 348 0 394 0 394 0 445 0.889 0 404 0 808 0 373 0 746 0 306 0 613 0 324 0 324 0 316 0 630
Triphenylphosphine, mmolea 0 569 1 252 0 634 1 528 0 694 0 685 0 748 0 771 0 683 1 536 0 682 1 407 0 593 1 379 0 566 1 258 0 649 0 637 0 648 1 425
Phenol, mg
158 244 706 648 248 201 158 77 186 202 202 292 203 349 136 270 184 107 490h 380
Reaction time, days 3 3 3 3 3
Ozonide reacted,
6
3 3 3 6 3 3 3 3 3
6
3 3 3 3
$c 96 9 97 9 96 6 97 9 95 3 98 7 96 2 97 6 95 3
99 98 99 97 97
7 5 4 3 5
90 9
92 98 97 96
i 8
4
8 97 4
Adjlisted for purity. 3,4-Diniethylphenol.
VOL. 37, NO. 1, JANUARY 1965
101
Table II.
Effect of Reaction Conditions on Reduction of 4-Methyl-2-pentene Ozonide by Triphenylphosphine Ozonide, mmole
Effect of air Effect of additives in n-heptane
Effect of additives in ethanol
Triphenylphosphine, mmole
Solvent Ethanol Ethanol n-Heptane n-Heptane n-Heptane n-Hep tane
0 771 0 748 0 932 0 677 0 764
0 0 0 0
455 455 411 411 0 411 0 411
0 0 0 0 0 0
0 394 0 394 0 388
0 431 0 431
664 740 522 498 531 504
Additive, mg. 156 Phenol 150 Phenol
Effect of temperature
0 0 0 0 0
396 396 396 388 327 0 327 0 327 0 327
0 0 0 0 0 0
689 575 563 854 563 563 0 563 0 563
solving in ether and washing with sodium bicarbonate solution to remove acidic materials. The ether iolution was dried over magnesium perchlorate and the product was redistilled. Procedure. A 200- to 300-mg. sample of the ozonide was placed in a 25-ml. measuring flask which was filled with nitrogen or carbon dioxide. The accurate weight of the ozonide was determined and the flask was filled to the mark with absolute ethanol. Air was removed from the solvent by addition of solid carbon dioxide. Five- or 10-ml. aliquots of the above solution were added to a flask containing a weighed sample of triphenylphosphine. An excess of about 100 mole yo of triphenylphosphine was generally used. S o further dilution with solvent was made. ,$bout 100 mg. of phenol were usually added although this is not necessary unless a nonpolar solvent such as heptane is used. The air in the flask was removed by the addition of solid carbon dioxide. The flask was stoppered and stored for a t least three days a t room temperature in the dark. About 30 ml. of acetone were added and the solution was titrated with 0.LV aqueous iodine solution. The end point is sharp and is recognized by the appearance of a yellow color which does not disappear upon standing. The presence of triphenylphosphine oxide or phenols did not introduce any errors or affect the sharpness of the end point. The results obtained with different ozonides are given in Table I using alcohol as the jolvent.
102
ANALYTICAL CHEMISTRY
Reaction temp., "C.
Ozonide reacted, CC
1 M. acetonitrile 1 M1. ethanol 900 3,4-Dimethyl-
72 144 16 16 16 16
25 25 25 25 25 25
Ethanol Ethanol Ethanol
77 Phenol 158 Phenol 500 3,4-Dimethyl-
72 72 65
25 25 25
97 6 96 2 96 2
Ethanol Ethanol
458 p-Chlorophenol 411 2.6-Di-tert-
72 72
25 25
94 0 93 4
1 4 22 65 0 33 0 50 1.25 2 00
25 25 25 25 98 98 98 98
25 62 86 95 76 86 92 93
phenol
phenol
butyl-4-methyl phenol Effect of reaction time
Reaction time, hr.
Ethanol Ethanol Ethanol Ethanol n-Heptane n-Heptane %-Heptane n-Heptane
...
... ...
DISCUSSION
Triphenylphosphine reduces ozonides to the corresponding carbonyl compounds. This reaction proceeds quantitatively and can be described by the following equation :
R2 where Ri is alkyl or hydrogen; RB is alkyl. If an excess of triphenylph6sphine is used, the unreacted triphenylphosphine can be determined by titration with iodine which is based on the following reactions :
The reduction of ozonides by triphenylphosphine must be carried out in the absence of oxygen since oxygen may oxidize the triphenylphosphine directly. Oxygen will also affect the
106 107 41 48 60 77
3 3 2 1 3 2
2 2 8 8 0 2 5 9
autoxidation of aldehydes yielding peroxides. Both of these reactions would cause an additional consumption of triphenylphosphine. The reaction was generally carried out a t room temperature since the ozonides might decompose at elevated temperatures. TThen the reaction was carried out in boiling n-heptane, however, decomposition occurred only to a small extent. (-1slow stream of nitrcgen was bubbled over the reaction mixture.) The rate of the reaction depended upon the solvent and was faster in a polar medium than in hydrocarbon. Phenols were effective ionizing solvents and accelerated the reaction in hydrocarbons. The effect of a number of reaction variables is given in Table I1 using 4-methyl-2pentene ozonide. With the exception of the first experiment on the effect of air, the air was removed by the addition of solid carbon dioxide. LITERATURE CITED
(1) Challenger, F., Wilson, Y. K., J . Chem. SOC.1927, 213. ( 2 ) Criegee, R., Kerckow, .4.,Zinke, H., Chem. Ber. 88, 18i8 (1955). ( 3 ) Homer, L., Jurgeleit, W., .4nn. 591, 138 (1955). ( 4 ) Lorenz, O., Parks, C. R . , J . Ora. Chem. in press. ( 5 ) LIair, R. D., Graupner, Alda J., A411AL. CHEM.36, 194 (1964).
RECEIVEDfor review August 27, 1964. Accepted November 9, 1964.
