TABLE I RELATIVE YIELDSOF RADIOACTWE PRODUCTS (NORMALIZED TO 100 FOR ACTIVITY I N P A R E T T I I Y D R O C A R B O N ) Molccules produced by mechanism ticscribed are boldface. 3Iytlrocnrl~oris:Ire rcpresrntcrl by :ipl)ropriate symbols: tlius butane; /=\ cis-butrnc, etc.
/v
Am
Tritiated products
_-___
IIydrocarbon
/W /\/
/”\
>=
/V\ /w\ +A=/ /V /W + He(l:50)
/v +
a
HP CIL 143 13 171 11 191 15 116 9 1T8 D 184 1.3 235 15 500
14 .i
/
//
3 1
41 4
A A 0
o o
I
5
0
0
0
33
0 0
3
0
0
15
o o
A/ >-
1 L Y . 1~
41 60
31 46
lO(1
69 21
58
42 23
5
6
1
50 49
0
75
0 0 0 100 44
0
o o 10
0 0
O
o o
12 14 0 4 22 0 101)“
/ - ‘/~ >.~~ //A A/“a
7 io0 1.7
ino
0
0
0 2
0
n o
n
4
0
0
0
1:;
n
o
(i
n
n
n
IOC 0
0 21
0 101)
0
so
r,
100
o o
o
n
(1
o
IO
8
o
n 8 0
(I
0
n
160 (50:l) n 46 n loo 4 0 4 0 Yield of butene-1 activity in this run reduced by order of magnitude compared to run cliiitaining no inntlerator. 01
alkane.2r3,4 Only small amounts of labeled degradation products, apparently formed by displacement of alkyl groups instead of hydrogen atoms, are formed. The present work on the reaction of recoil tritium with alkenes indicates the existence of an additional reaction mechanism. .4s with alkanes (see Table I, butane) about 60-S0yO of the tritium is found in H T and the labeled parent molecules. However, appreciable yields (10-20%,) of labeled degradation products are also found. Table I shows that the yield pattern of these unsaturated fragments varies in a very specific manner with the alkene reagent. The following mechanism for this “fragmentation” reaction is postulated. A tritium atom, having some residual recoil energy, adds on to the double bond of the alkene, forming a “hot” radical. This radical then decomposes by cleaving a carboncarbon bond without rearrangement, to form a smaller radical and an olefin. Because the tritium atom carries excess energy, it will attack the double bond indiscriminantly and form approximately equal amounts of both possible “hot” radicals. CII3CHzCHzCH=CH2 507, C H ~ C H ~ C H Z C H T C--+ H~* CH3CHzCFIZ. CHT=CH?
+4 L)
+
50% CH3CH?CHzCH*CH2T +
CH3CHz’
+ CH2=CTICII?T
For example, the tritium atom will react with pentene-1 as shown, t o give similar amounts of tritiated propylene and ethylene. From pentene2, however, the same reaction will yield butene-1 and propylene. This mechanism is in accord with results on the decomposition of deuterated butyl radicals a t 500°.5 Since addition of a hydrogen atom t o a double bond is exothermic, t h e reaction probably could proceed at thermal energies. However, in the presence of an excess of helium as a moderator, the yields of t h e labeled fragments, as well as the yield of the parent molecule, are reduced greatly. On the other hand, these products are unaffected by the presence of a small amount of oxygen as (2) M. El-Sayed and R. Wolfgang, THIS J O U R N A L , 79, 3286 (1957) (3) hl. El-Sayed, P. Estrup and R . Wolfgang. J. P h y s . C h e m . , 62, 1356 (1958). (4) D. Urch and R. Wolfgang, unpublished work. (5) J. McNesby, D. Drew and A. Gordon, J . Chcm. P h y s . , 24, 1260 (1956).
+
A=/
0
scavenger. Therefore, this reaction to form labeled fragments apparently also takes place before the recoil tritium reaches thermal energies. Thus, while this is not a “hot-atom” mechanism occurring only a t very high kinetic energies, it may be termed “epithrrmal” to denote that it competes effectively only a t energies above the thermal range. This mechanism accounts for the results so far at hand, some of ivhich are sliown in Table I. II’ork to demonstrate the further predictions of this rriotlel is continuing. The authors wish to thank Profcssor IT. noering for his interest and criticism. CHEMISTRY DEPARTMEST YALE UNIVERSITY S E W IIAVES, C O X N E C T I C K r
11.iVIn RIC17ARD
L.
s.
GRCIX \vC>I.FC.ASG
RECEIVED FEBRL-.XRY 11, 1050 COENZYME Q.
VIII. STRUCTURE STUDIES O N A PLANT QUINONE
Sir: We have isolated from alfalfa a quinone having coenzyme Q-like activity’; structural data support I, 2,3-dimethyl-5- 13’-methyl-2’-butenyl-oktakis(3’-methyl-2’-butenylene) ]-benzoquinone.
’
C H a G H CH;’
CH, 1
(C,H,CH=CC€I,),H
I. r = 9 11. n = 3
0
Crane and L e ~ t e risolated ~,~ from alfalfa a quinone (Q-254), m.p. 42-43”, which appeared t o be a trimethylbenzoquinone with a fourth substituent of nine mono-unsaturated isoprenoid units. Kofler reported4 a substituted benzoquinone, 1n.p. 48-49”, from alfalfa. of Q-254 and The coenzyme Q-like studiesj-8 on “unidentified factors” in alfalfa in ( I ) Kindly tePted by D r . 1:. L. Crane, Cniver,ity uf Texas, Austin ( 2 ) F. L . Crane a n d R. L. Lester, P h n f P h y r z o i . , 33, (Suppl.) V I 1 (1958). (:1) F. L. Crane, ibid., in press. [ A ) M. Kofler, “Jubilee Volume, Emil Barell,” F. IIoffmaniiLaRoche and Co., L t d . , Basel, 19-16. ( 5 ) M , G. Vavick, A . Werty a n d A. R. Remmerer, Polrilry Scr., 32, 433 (1953). (6) H. M. Scott, II. Fisher a n d J. 51. Snyder, i b i d . , 32, 5 X (1953). (7) C. H. Hill, R. L. Borcbers, C. \V.Ackerson a n d P. E. Xfussehl, ibid., 32, 775 (1953). (8) B. March, J. Biely and S. P. Touchburn, i b i d . , 34, 968 (1955).
April 20, 1050
CO\INUNIC.\TIONS
TO T I I B E D I T O R
2027
animal nutrition, particularly in chicks, prompted acidic reagents, we have found t h a t 2-osa-1,2dihydro-cizdo-dicyclopeiitadielie1-3 (11) resists the us t o examine t h e plant quinone. Extraction of commercial alfalfa nieal with rearrangement t o the cso-configuration characpetroleum ether followed by chromatography on teristic of its hydrocarbon analog.' Stabilization Florisil and on Decalso yielded a crystalline yellow of the initial carbmium ion bv the 2-oxa atom is 'I'he = 217 proposed t o explain the anomalous beha\.ior. quinone, m.p. 4S-49°.9 Ultraviolet: at 254 mM and 2% at 2G2 mfi in isoijctane. Reduc- steric possibility of such participation is proved by tion with sodium borohydride gave t h e hydroqui- cyclization of 2-aza-l,2-dihydro-endo-dicyclopentadiene (111) with hydrobroniic acid (4S5-A) followed none: = 48 a t 290 mp in ethanol. The infrared spectrum in carbon disulfide differs from t h s t by 23\70 sodiuni hyclrouide yielding the tertiary of coenzynie Qlo niainly in t h e absence of the in- amine IV, t h e first nieniber of a new heterocyclic tense i . S fi band associated with t h e methoxyl ring system. .hiitic 1V is identical with structure V. function ; all other functional bands are similar. The n.m.r. spectra'" of I and its side-chain reduction product and of 2,3-dimethyl-5-farnesylbenzoquinone (11) and its side-chain reduction product when interpreted in coinparistin with the spectrum of QltI1lled to structure I for alfalfa quinone. I t shows a ring proton as a triplet a t 4.5, G, and 7 c.11.s. aiid no metlioxy protons. The latter are replaced by ring CH3-functions which show a t 1'7s C.P.S. in the side-chain reduction product which I I1 Ill does not have t h e interference caused by t h e =C-CH2-CH2-C-= functions. T h e fact t h a t the ring proton is a triplet and not a quartet significs t h a t its ortho group is the side-chain - C H r and nut CHa--. Since the ring methyl protons are not spin-coupled, no ring proton is ortho to them. The ratio of t h e area of the doublet a t 131, 141 C.P.S. to the ring proton triplet is 2 t o 1. Thus, only one long side-chain is present ortho to t h e ring prc'tori, and the two ring CHa- are ortho t o each other. This is confirrned by the G to 1 area IV V VI ratio of the ring CHa- resonance (1'7s c.p.s.) to the The secondary amine I11 (iii.p. 117-110" with riiig protoil resoiiance in t h e quinone reduction product. A11 these tleductioris are quantitatively sublimation a t about 55". Calcd. for CgH13N: supportetl by the ri.ii1.r. spectra of %,3-diniethyl-3- C , T9.93; H, 9.69. Found: C, "3%; €1, !I.Sl), famesyl-1 ,Lbenzoyuiiioiie aiid its side-chain re- prepared by lithium aluniinuin hydride reduction of endo-bicyclo[2.2.1 ]-3-heptene-2,3-dicarboxylicacid duction product. forms an 2,:~-~iiiicth~l-3-farnesvlbciizo~luirioiic (11) was imide"-7 by t h e method of Rice, et alkali insoluble benzenesulfonamide (m.p. 107synthesized from 2,:3-diiiicth!lli\idrocluiiio~ie and fariiesol as a yellow oil; a n d . Found: C, S1.39; 10s". Calcd. for CI5H1;NSO2:C, G5.42; H, (3.22. H, 9.22; ultralriolet iii isoiictarie, EM = 1S,OO0 a t Found: C, G3.2(i; H , G X ) , and is reduced readily 233 i i i ~ ,ant1 15,SOO a t 261 m u . Coiiibiiiirig this by catalytic hydrogenation t o the saturated amine, with the ultraviolet data of t h e alfalfa quinone isolated as the beiizciic.sulfonamidc ( 1 n . p 168l(iS.5". Calctl. for C15HIt,KSO~: C, G1.95; H , leatls t o ;t value of 9 for 11 in I. (3.00. Found: C , G1.W; 11, G.7G). The tertiary (9) Cr;inc's Q-224 a n d uiir (,'tinone were 1101 wparate(l on amine IV (n1.p. 126-128" with sublimation a t iiiiprcxiiate
