COMMUNICATIONS TO THE EDITOR
June 20, l O G O
321'7
(102.7 mg.) was dissolved in 10 ml. of methanol and the substance t o be identical with the product obtaincd through solution treated with 1 ml. of 3.2 N methanolic ammonia. the acetylation of 1-0-mesitoyl-a-D-glucopyranose as dcAfter 23 hr. at 20' t h e mutarotation had ceased. T h e soluscribed below. tion was then evaporated t o dryness a n d the residue crystalFurther elution of the alumina with acetone (500 ml.) lized from ethyl acetate-pentane t o give 72 mg. (70%) of gave 434 mg. of sirup. Neither this material nor a n y of melting at 188-190". Two rethe other fractions from the chromatography crystallized 2-0-mesitoyl-~-~-g~ucose when seeded with 1,3,4,6-tetra-0-acetyl-2-0-mesitoyl-P-~-crystallizations from ethyl acetate afforded pure material melting at 192-193'. glucose.4 I n earlier work' 2-0-mesitoyl-~-~-glucosewas reported 2,3,4,6-Tetra-0-acetyl-l-0-mesitoyl-~~-~-glucose (VIII) t o melt at 180-187O and mutarotate in water (c 0.94) from 1-0-Mesitoyl-a-D-glucose (VI).-1-0-Mesitoyl-a-D+24.0° (13.5 min.) + +45.5" (19 hr.), T h e sample preglucopyranose (50 mg.) was added t o a mixture of acetic After anhydride (0.12 ml., 8.3 molar equivalents) and pyridine pared at t h a t time was later found t o melt a t 188-190'. two recrystallizations from ethyl acetate, i t gave, with little ( 1 m l . ) . The mixture was kept overnight a t room temperaloss, material melting at 192-193' and rotating [ C ~ ] * ~ D ture and then diluted with water and the product extracted f19.8" (16emm.) -+ +45.4" (28 hr., constant) (Hz0, with methylene chloride ( 2 X 10 ml.). T h e combined extracts were washed successively with 3 N sulfuric acid c 0.66). This product did not depress the melting point of t h a t obtained a s described above through the rearrange(2 X 10 m l , ) , saturated aqueous sodium bicarbonate ment of 1-0-mesitoyl-a-D-glucopyranose. T h e infrared ( 2 X 10 ml.) and water (2 X 10 ml.). Moisture was removed with sodium sulfate a n d the solution, after filtra- spectra of the two samples were identical. tion through decolorizing carbon, concentrated in wacuo Anal. Calcd. for C1eH2207: C, 58.88; H, 6.80. Found: t o dryness. From ethanol-pentane the residue yielded C, 58.91; H, 6.52. 42 mg. (55%) of 2,3,4,6-tetra-0-acetyl-l-~-mesitoyl-a-~glucose melting a t 119-120' either alone or in admixture with Acknowledgment.-Analyses were carried out in a sample made earlier' through the fusion of a mixture of a-D-glucopyranose pentaacetate, mesitoic acid and zinc the Institutes' Analytical Services Unit under the chloride. T h e infrared spectra of t h e samples from the direction of Dr. W. C. Alford. two sources were identical. 2-0-Mesitoyl-p-D-glucose (VII) from 1-0-Mesitoyl-a-Dglucopyranose (VI).-1 0 Mesitoyl a - D - glucopyranose BETHESDA14, MD.
- -
-
COMMUNICA'1'IOIVS CHEMICAL EVIDENCE F O R A TRIPLET GROUND STATE FOR METHYLENE
Sir: We have found what we believe to be conclusive chemical evidence that the methylene molecule possesses a triplet electronic ground state. Herzberg and Shoosmith' already have obtained spectroscopic evidence for a triplet state of methylene. In more recent work, * results were obtained which suggest that the flash photolysis of diazomethane yields methylene molecules in highly excited singlet states which are subsequently energetically degraded to the triplet ground state through collisions with inert gas molecules. The most intense spectrum for the triplet state was obtained when a large excess of nitrogen was present. On the other hand, all of the previous evidence based on the observed chemistry of methylene was consistent only with a singlet (not necessarily ground) state for this molecule.3 Skell, et al.,3have found that the 1,2-dimethylcyclopropane formed from methylene and cis- or trans-2-butene in the gaseous or liquid phase is almost entirely the cis or trans isomer respectively. These workers felt that this stereo( 1 ) G . Herzberg and J. Shoosmith, N u l r i r e , 183, 1801 (19.59).
(2) G . Herzberg, paper presented at the R . A. Welch Foundation, Conference on Chemical Research, Nov., 1959. We are grateful to Dr. Herzberg for a copy of this manuscript prior to its publication and for further unpublished information concerning the conditions which are necessary for the observation uf methylene in the triplet state. (3) R. C. Woodworth and P. S. Skell, THIS J O U R N A L , 81, 3383 (1959); and references therein. In some substituted methylenes there is evidence of triplet states [R. hl. Etter, H . S. Sko\ronek and P S. Skell, ibid., 81, 1008 (1969); P. S. Skell and J. Klebe, zbid., 82, 248 (1960)l. In none of these cases has the ground state been characterized.
TO THE EDITOR specificity implied a singlet state for methylene under these conditions. We have repeated the work of Skell and are in full agreement with his conclusions. However, we have extended the study of the photolysis of diazomethane in the gas phase to systems containing only small partial pressures of diazomethane and an alkene in the presence of a large excess of nitrogen. These are the conditions found by Herzberg to be most favorable to the formation of methylene molecules in the triplet ground state. Under these circumstances the stereospecificity of the reaction is entirely lost. In fact, in the reaction with &-%-butene there is a complete reversal of the proportion in which the cis- and trans-l,2-dimethylcyclopropanes are formed. I t is evident from the data in Table I that the reaction becomes less stereospecific as the amount of nitrogen present during the decomposition is increased. This is most noticeable in the reactions with cis-2-butene. Our interpretation of the observations is presented. The methylene molecule when first formed is in a singlet state and thus gives rise to reactions which are almost entirely stereospecific as the tm-o new bonds may be formed simultaneously.3 When a large excess of nitrogen is present the methylene molecules undergo numerous collisions with the nitrogen molecules before striking an alkene. The collisions with the inert gas degrade the methylene molecules through their excited states to the ground state which in view of the loss of stereospecificity is a triplet. The combination of a methylene molecule in a triplet state (CH2[.f .f 1 ) and a butene niolecule must give rise to an intermediate which is
;$2I h 'rAR1.E
1
Cnnvetitional high vacuum line techniques were used t o purify and transfer t h e gases. All manometric measurernents were performed with a Bourdon spoon gauge t o avoid any contamination with mercury vapor. All of t h e reactions were carried only a few per cent. t o completion; most of the diazomethane decomposed on t h e walls of t h e flask. T h e products of t h e reaction were separated b y vaporliquid partition chromatography using both silicone oil and silver nitrate in propylene glycol columns. T h e products were identified ( a ) by preparing authentic samples and comparing their elution times on t h e two columns and (b) by infrared analysis of t h e individual bands obtained by the chromatographic separation. The nature and proportion of the other products formed will be discussed in a future publication
-
ii3 ? Riitene
R e a c t a n t c o n c n s in m m /inns-2Diazo Butene methane
370 1.1 (1.6
n
0
3.57 2.1
0
(I 0
40(1
1 ,6 5. 9
-.'")3 5.1
- Nitrri Ern
- Prod u e t r a t i o s " --. i-isvl . 2 Ditrans-1.2methyl Ilimethyicyclo cyclopropane Iiropane
100
1%
101
I(J0
c-
560 0 FG3
1.5 IOh
100 100
18"
100
(I
I
I)
As dcterniiiied from tlic relative l~aiitl areas in the chromatography experiments. These are typical runs ; all have been done a t least in duplicate. Under all conditions the dimethylcyclopropanes make up approximately 50% of t h e Cj fraction, and this fraction is t h e major one apart from unreacted, unisamerized butene. These represent upper limits for cis-1,2-dimethglc~clopropane.A correction for t h e small amount of 2-methyl-2-butene present mas not made in these two cases.
'The present evidence then favors thc linear structure for the ground state of iiiethylenc. 1)EPARTMENT OF CHEMIS'iXY 1:. -4.I,. .\SET ~ ' N I V E R S I T Y O F OTTA\VA I I;KON
itself in a triplet state. In this case, as pointed out P.\PS by Skel13the final bond formation step to form the cyclopropane ring may proceed only after the in1:ractiori added" termediate has suffered sufficient collisions to un- Practioii -1 + boiled I? + I'rSS dergo a triplet-to-singlet transition. The lifetime Fraction B + boiled A + PrSS of the intermediate in the triplet state is of suf- Fraction A + fraction R + PrSS ficient duration t o allow for its i~omerization.~Fraction -1 + fraction R - PrSS Therefore, the reaction may be envisaged as
S;illite i < , r n i e < l'I , (mrmoles)
0.:3
11 2 7. ii !I, 9
* Reaction niisture of 0 7.5 1111. cciiitaiiictl in piii(ile>: 'irk, p1-I 7 . 5 , 2 5 ; ethylenediamirietetraacetate, 0.6.5: MgClT, 2 . < 5 glucose-6-phi,spliate, 2 . 5 ; T P Y + (oxidized triplinspliopyridine nucleotide), 0.31: S n P S 0 3 ,2 . 5 : PAPS35(11J15 cpm ' inpmole), ! ) , 5 0 ; glucose-R-plir,spliate dehydrogeiiaqe (%1 units/'tng. protein), 0.8 unit: Fraction A , 0.231 rng. protein; Fraction B, 0.070 ing. protein; PrSS, 1.67 ing. 1;r:tctirins A and B were prepared frrm extracts ( i f > e a s t ;tcet~iiic powder treated with 4 volumes of 0.1 S HZS04saturatetl irith ( SH4'tSOa. After removal (if denatured protein froin the resuspended precipitate, Fraction A was obtained by precipitation frnm 0.57 t i l 0.80 saturated (SH4bSO; Fraction B was obtained by precipitation from 0.36 t o !).57 saturated ( S H , l p S O , and reprecipitated from 15 til 2 ' , rthanol. Sulfite fommed i n 2 hr. :it 3;' \YR' tletertiiincti as previously described.2
hicubation o f PrSS with Fraction rZ or ;i furthcr purified Fraction X-1 m c l T P N H leads to the oxidation of T P N N and thc. :tppearancc of -SH (Table llolecular orbital theory predicts that the methylene molecule if bent should possess a singlet ground state ('A1) while if it is linear (or nearly so) it should possess a triplet ground state L).~ 1 4 ) R . J . CvetanoviC [Ca?z. J . C l i e i n . , 36, 623 (I95S)j h a s a l r e a d y ol,served t h a t t h e r e a c t i o n of oxygen a t o m s in the t r i p l e t s t a t e with e i t h e r r i s Clr / i c i i i ( ?-iiiitene produce.: a m i x t u r e of t h e cis a n d f i n ~ i s i,!lrtyi,lv.. ,,ti 4 I t LVal\li. ./ i l , e m f ~ < ~ rint e dp a r 1 114 l h r Nationdl hcicllir \\-e are i n d r h t r d 1,) 17,- I I< 7 l r u n n r r and Alr. X I . I ' Foundation T h n n i p i o n for ?iltracc,ntrifirgr s t i i d i e i and t i , I l r S Shiirin irr rietc t h e :3?5 m p a h w r h e n c y o f Pr. ( 2 1 I,. G . Wilson a n d 11. Xmidiirshi, 'i'irls J U U R S A I . . 8 0 , gX>71, ( I Ul.58) [.?) H. Hilz arid AI, K i t t l e r . I i i w c l i p i 8 ~ b z o p l i ~ s a c l i i , 3 0 , t 6 C l (l!1581. ) AI, I s h i m o t o .I. J > i o ~ - / : ~ 1,n' , H 1) P e c k . J r . . Pi.ni- \ t i / ) I , (; U ' i l w n i , 'I' . A w I i i :in(
