3472
JOHN
L. KICEA N D EVAH. MORKVED
The ether filtrate was kept 66 hr. a t -20'; i t deposited crystals of rac-methyl (3,4-dimethyl-3,4-dihydroxyhexanedione-3,,5) cyclic phosphate ( I I I b , 10.1 g., 39Lj,, crude m.p. 4 5 5 0 " ) . Recrystallization from dry ether ( i n the absence of mozsture) gave colorless crystals of racemic diketol phosphate I I I b , m.p. 54-56', Analysis was performed immediately. The s o l d phosphate deteriorates on standing, even under nitrogen, hut is conveniently stored under ether a t 5". A n d . Calcd. for C ~ H I ~ O G P C,: 43.2; H , 6.0; P, 12.4. Found: C, 42.5; H , 6.0; P, 11.6. The infrared spectrum was taken in dry CCll (q): 5.80 (1725 cm.-') ( s ) with shoulder a t 5.83 [in CCla the meso isomer shows a distinctly split carbonyl at 5.81, 5.84 p ] ; 6.90 ( w ) , 7.04 ( w ) , 7.25 ( m ) , 7.38 ( m ) ; 7.68 (1302 cm.-l) ( v . s.); 8.93 ( i n ) ; 9.51 (1052 cm.-l) ( v . s . ) ; 9.98 ( m ) , 10.1 (shoulder), 10.4 ( w ) . HI n.m.r. spectrum in CDCls solution ( 7 ) : doublet a t 6.00, J H P 12 c.P.s., two singlets of equal intensities a t 7.60 and 7.65 and two singlets of equal intensities a t 8.43 and 8.53; see Fig. 6 (the spectrum does not change on standing, in the absence of moisture). The ether filtrate from which the racemic diketol phosphate I I I b had separated was concentrated and cooled 24 hr. at - 10". Crystalline hemiketal cyclic phosphate 1L.a (2.4 g., 9'~;, m . p . 72-82' ) separated out. Hydrolysis of meso-Diketol Cyclic Phosphate (IIIaj to meso3,4-Dimethyl-3,4-dihydroxyhexanedione-2,5(Va).--A mixture of the mesodiketol phosphate I I I a (11.185 g . , 1n.p. 105-110"). benzene (60 nil,), and water (4.02 ml., 5 mole equivalents) was kept 1.5 hr. a t reflux temperature. The aqueous acid layer was separated, saturated with S a C I , and extracted with benzene. T h e combined benzene extracts and original layer were dried ( MgS04) and evaporated in vacuo. Colorless needles of meso3,4-dimethyl-3,4dihydroxyhexanedione-2,5 (\'a) (6.1 g., 80':;, m.p. 89-92') were obtained, analytical sample m.p. 9 5 9 6 ' (hexane). Anal. Calcd. for CgHlr04: C , 55.2; H , 8.1; mol. wt., 174. Found: C, 54.6; H , 8.2; mol. w t . , 215. The infrared spectrum was obtained in CClj ( p ) : 2.90 (3460 c m . - l ) ( s h a r p ) ( n i )(OHstretching); 3 . 3 4 ( w ) , 3.40(w), 5.86(1707 cm.-l) (s)(C = 0 stretching); 6.85 ( w ) , 7.02 (w). 7.30 ( s ) ( O H deformation); 8.23 ( s ) , 8.76 ( s ) (C-0 stretching); 9.35 ( m ) ; HI n.m.r. spectrum (in CCL, T ) : singlets a t 5.50, 7.64, and 8.75; intensities: 1: 3 : 3 ; bis-2,4-dinitrophenyI-hydrazonem.p. 2092 10' (chlorobenzene). Anal. Calcd. for CZOH~ZOIOXS: C, 45.0; H, 4.1; N , 21.0. Found: C,45.2; H , 4 . 0 ; K , 20.9. Hydrolysis of mc-Diketol Cyclic Phosphate IIIb to rac-3,4Dimethyl-3,4-dihydroxyhexanedione-2,5 (Vb).--A mixture of the rac-diketol phosphate I I I b (6.57 g., m . p . 50-52'), benzene (30 ml.), and water (1.9 m l . , 4 mole equivalents) was kept 1.15 hr. a t reflux temperature and worked up as for the meso isomer. h colorless oil (3.7 g., 80:;) was obtained; this was stirred with 5 mi. of warm hexane and the mixture was kept 20 hr. a t 5 " . X
[CONTRIBCTION FROM
THE
VOl. 85
small amount of crystalline meso-diketol V a (600 nig., 1 3 ' 1) was filtered off. The hexane was evaporated and the residue (2.72 g., SO(!L ) was submitted t o short-path distillation; icil--3,1-ditnethyl-3,4-dihydroxyhexanedione-2,5 ( V b ) (2.21 g . , 48');) had b.p. ca. 45-50" (0.3 m m . ) , ~ 2 1.4495. 6 ~ Anal. Found: C, 55.7; H , 8.2. The infrared spectrum in CCI, had bands a t ( p ) : 2.87 (3480 cm.-* (mw, broad) ( O H stretching); 3.34 ( w ) , 3.40 ( a )5.88 (1702 cm.-l) (s) (C-0 stretching); 6.90 ( w ) , 7.02 ( N - ) , 7.18 (ms), and 7.32 (Ins) ( O H deformations); 7.96 ( w ) , 8.10 (w), 8.26 ( m ) , 8.47 ( i n ) , 8.76 ( s ) with shoulder a t 8.93 ( s ) (C-0 stretching); 9.22 (rn); H L n.1n.r. spectrum (in CCId, T ) : singlets at 5.73, 7.77, and 8.70; bis-2,4-Dinitrophenylhydrazone, i n . p . 200202' (chlorobenzene). Anal. Found: C, 45.5; H, 4.3; S ,20.7. Hydrolysis of the Crystalline mesu-Oxyphosphorane ( I I a ) with an Excess of Water.-.I solution of crystalline adduct I l a (10.08 g.) in benzene (50 ml.) containing some water (3 n i l . ) was kept 30 rnin. a t reflux temperature under S 2 . T h e layers were separated; the water-acid layer was saturated with FaC1 and extracted with benzene; the dried benzene layer plus extracts were evaporated. The crystalline residue was recrystallized from hexane; first crop of diketol \'a, 4.81 g.; second crop, 0.34 g. (yield 93';; hoth melting a t 94-95' 1). This hydrolysis of IIa was repeated using water enriclicd with 10.61 atom ii 0lg, 0.179 atom :G 0 ' 7 , arid a n unspecified amount of deuterium ( V E D A , Research and Developmeiit Co., Israel), in order to establish possible incorporation of Ole into the diketol during the hydrolysis. The meso-diketol of normal isotope content was kept in contact w i t h 0'8-enriched water, in refluxing benzene containing some phosphoric acid, as in the hydrolysis experiment, in order to determine possible incorporation of OI8 into the diketol as a result o f an exchange with the water. T h e three samples of diketo1 were submitted to mass spectrometric analysis, with results which will be described elsewhere. Hydrolysis of the Original Mixture of Diastereomeric Oxyphosphoranes IIa and IIb with a n Excess of Water.-The original distilled mixture of meso and racemic adducts IIa and I I b (66.81 g.) was dissolved in benzene ( 3 5 0 ml.), treated with water (about 12 nil,), and carefully warmed up t o initiate a vigorous reaction. The mixture was kept 1 hr. a t reflux temperature and worked u p as for the n m o isomer, Fractional crystallization from hexane gave crystalline diketol Va, m . p . 94-95", in 63' yield. Distillation of the liquid residue gave the ruc-diketol i - b , Y L ~ ~ I1.4491 I in about 205; yield. I t is dit?icult t o obtain rer-Vb cornpletel]- free from meso-\*a by this procedure ( d e supra).
Acknowledgment.-We are grateful to Dr. J . Lancaster of the American Cyanamid Co. (Stamford, Conn.) for the P3In.m.r. spectra a t 16 Mc. a'sec. and to Prof. E. Eliel of the University of Notre Dame and Dr. E. 51. Banas of the Xmerican Oil Co. (Whiting, Ind.) for facilities and instruction in H 1 n.m.r. spectroscopy.
DEPARTMEST O F CHEMISTRY, ORECOX
STATE C'FIVERSITY,
CORVALLIS, O R E . ]
Mechanisms of Reactions of Sulfinic Acids. V. The Mechanism of the Alkyl Sulfide-Sulfinic Acid Reaction' BY JOHN L. KICEA N D EVAH . MORKVED RECEIVED J U X E 17, 1963 The mechanism of the recently discovered$ primary alkyl sulfide-p-toluenesulfinic acid reaction has now been determined. The relative reactivities of a,a-dideuteriohenzyl sulfide and its undeuterated analog show the reaction is subject t o a large isotope effect ( k ~ / = k ~5 . 2 ) . This fact, combined with the variation of rate with sulfide structure for a series of sulfides ( K C H 2 M and the previously reported2 dependence of rate on other reaction variables, requires t h a t the rate-determining step be eq. 2B. Experiments with butyl a-acetoxybutyl sulfide show t h a t the cation KCH=S-CH&+ produced in reaction 2B will be immediately hydrolyzed t o R C H O and KCH*SH, and t h a t the mercaptan will then react extremely rapidly with some of the remaining sulfinic acid. Other experiments show t h a t under the present reaction conditions this mercaptan-sulfinic acid (XrSO2H) reaction gives as products, almost exclusively, the two thiolsulfonates ;\rSOnSAr and ArS02SCH2K. The course of the sulfide-sulfinic acid reaction subsequent t o t h e rate-determining step is thus as shown in Chart I . Additional kinetic studies demonstrate t h a t any small amount of disulfides produced along with the two thiolsulfonates in the mercaptan-sulfinic acid reaction will be rapidly consumed by further reaction with sulfinic acid, in a process which also yields the two thiolsulfonates above as products.
Kice and Bowers2 recently described a new reaction between p-toluenesulfinic acid and primary alkyl (1) This research supported by the Directorate of Chemical Sciences. Air Force Office of Scientific Research, under Grant AFOSR-108-63
sulfides, which leads to the cleavage of the sulfide and the oxidation of one of its alkyl groups to the corresponding aldehyde. Other reaction products are the (2) J . L. Kice and K. W. Bowers,
J. A m . Chem. Soc., 84, 2380
(1H82)
XLKYLSULFIDE-SULFINIC
Nov. 5 , 1963
34T3
~ C I DREACTION
p-tolyl and alkyl p-toluenethiolsulfonates, the over-all stoichiometry being as shown in eq. l . 3 Kinetic study 5ArS02H ( R C H Z ) Z+ S
+
Ar
2AhS02SAr P-CHsCsHa-
=
+ ArSOzSCHZR + R C H O + 3Hz0
1
(1)
of the reaction in moist acetic acid showed that it was first order in both sulfide and sulfinic acid. This. and the response of rate to such additional reaction variables as water and strong acid concentration, pointed clearly to a mechanism of the general form shown iii eq. 2 but did riot elucidate the exact nature of the change taking place in the ratedetermining step. ArS02H
+ ( IiCH2)2S+ H +
Ar-S-&CHqRh
f €120
I1
0
(2)
0.0081.0
rate
Xr-S-S( CH21l)~ ~-
--+
final products after several steps
determining
I
0
+/CHzR
4
ArSOnH
CHzR rate
detnI-
/I
H
R
viously,' sulfinic acid is consunied in such systems by both the alkyl sulfideesulfinic acid reaction, which is first order in sulfinic acid, and by disproportionation to thiolsulfonate and sulfonic acid, a reaction which is second order in sulfinic acid.j Since the sulfide is present in considerable stoichiometric excess, ks(RpS) remains effectively constant throughout a run. For the faster reacting undeuternted sulfide the ks term in =
+
Ks(l
