NOTES
41'72
solid, m.p. 257-261", was obtained which analytical data indicated to be the monohydrochloride salt. Anal. Calcd. for C ~ I H I ~ C I N Z OC, Z : 53.99; H , 7.01. Found: C, 54.12; H , 6.92. An attempt t o replace two phenolic hydroxy groups b\. using a ratio of two moles of 1-methylpiperazine t o one mole of phloroglucinol dihydrate yielded the same monosubstitution pr.oduct as described above. l-Methyl-4-(3',5'-dimethoxyphenyl)-piperazine(11). A . From 3,5-Dimethoxyaniline.-A mixture of 2.8 g . of 3 , M i methoxyaniline, 3.5 g. of N,N-bis-(p-chloroethyl)-meth>-lamine hydrochloride, and 20 ml. of methanol was refluxed for 17 hours; 1.1 g. of sodium carbonate was added, and heating was continued for 20 hours more. The mixture was filtered, concentrated and made basic with aqueous sodium hydroxide. An organic layer which formed was extracted into benzene and distilled. After a forerun of 3,Sdimethoxyaniline there was obtained 0.7 g. of colorless oil, b.p. 128-130' a t 0.1 mm. The maleate salt, m.p. 145-146', was prepared in isopropyl alcohol, and recrystallized from isopropyl alcoholether mixture. Anal. Calcd. for C17H21S~06:C, 57.94; H , 6.87. Found: C, 58.19; H , 6.72. A solution of the oil in absolute alcohol was treated with methyl iodide. After three days the white crystals of 1,ldimethyl-4- (! ',5 '-dimethoxypheny1)-piperazinium iodide, m.p. 229-230 , were collected and dried. Anal. Calcd. for C I ~ H ~ J N Z ~C,Z :44.45; H, 6.13. Found: C, 44.52; H , 6.09. B. From l-Methyl-4-(3',5 '-dihydroxypheny1)-piperazine. -A solution of 0.5 g. of l-methg1-4-(3',5'-dihgdroxvphenylbpiperazine in 25 ml. of methanol was treated with a solution of about 1 g. of diazomethane in ether. The red solution was allowed t o stand overnight, and was then concentrated. The residual oil was distilled to obtain 0.2 g. of yellow oil boiling a t about 125' a t 0.1 mm. The maleate salt was prepared in isopropyl alcohol and ether. The melting point was 144-145', not depressed by material from method A. Anal. Calcd. for C17H24S206:C, 57.94; H, 6.87; N, 7.95; 0, 27.24. Found: C, 58.00; H, 6.88; N, 8.14; 0, 27.22. The methiodide wa? prepared in ethanol and recrystallized twice from this solvent. The shiny platelets had a melting point of 230-231", not depressed by mixture with material from method A. Anal. Calcd. for C14H2rINz02:C, 41.15; H , 6.13; S, 7.41. Found: C,44.45; H , 6.38; S , 7.27. ABBOTTLABORATORIES XORTHCHICAGO, ILLISOIS
Ring-size and Conjugation Effects on the Carbonyl Vibrational Frequency of Some Benzocyclanones and Methylacetophenones BY IT.M. SCHUBERT A N D 11;. A. SWEESEY RECEIVED FEBRCARV 14, 1955
The carbonyl absorption frequency in the infrared of aromatic ketones is known to be lower than that of corresponding aliphatic ketones.' The frequency is not noticeably influenced by a change of the alkyl group attached to the carbonyl from say methyl to ethyL2 However, the carbonyl frequency of an aromatic ketone is shifted toward the aliphatic frequency by steric inhibition of phenyl-arbonyl conjugation. In Table I are given comparisons between the (1) See, e . & , F. A. Miller, "Organic Chemistry." Vu]. 111, H. Gilm a n , Editor, John Wiley a n d Sons, Inc., S e w York. S . Y., 1953, p p . 122 ff. (2) D. Biquard, Bull. BOG. chim., [.5] 8 , 55 (1941). (3) R. H. Saunders, 31. J . M u r r a y and F. F. Cleveland, T H I S J O U R N A L 63,3121 (1941).
Vol. i 7
carbonyl frequency of methyl ethyl ketone and some alkyl acetophenones. It is evident that not all the shift in frequency from aliphatic to aromatic carbonyl can be attributed to conjugation with the benzene ring. Thus, 2,6-dimethylacetophenone and acetomesitylene, which according to their ultraviolet spectra are practically completely inhibited from c~njugation,~a,b still show a carbonyl vibration shift of 18 crn.-l from methyl ethyl ketone. The shift in carbonyl frequency from methyl ethyl ketone is approximately the same for omethylacetophenone and 2,4-dimethylacetophenone as for acetophenone, although ultraviolet spectra indicate a partial inhibition of resonance in the former two compounds.j The average value for this "benzene-ring effect" for the completely or partially conjugated ketones is 33 an.-'. TABLEI A COMPARISOS OF THE CARBOXYL YIBRATIOSAL FREQUENCY OF SOME ALKYLACETOPHENONES WITH THAT OF METHYL ETHYL KETONE" Compound
Cm.
-1
Shift f r o m CHzCOEth,C
Methyl ethyl ketone 1718 0 1686 32 Acetophenone o-Methylacetophenone 1688 30 2,4-Dimethylacetophenone 1683 35 3,4-Dimethylacetophenone 1681 37 2,6-Dimethylacetophenone 1700 18 Acetomesitylene 1701 17 Average a All compounds measured as pure liquids. shift for conjugated and partially conjugated ketones, 33 cm.-'. Average shift for unconjugated ketones, 18 cm.-I.
Benzocyclanones ; Ring-Size Eff ect.-It is well known that the carbonyl stretching absorption band for cyclic ketones varies with ring size.6aib,C The frequency decreases as the ring size is changed from cyclobutanone up to cyclohexanone, continues to decrease more slowly in the medium ring ketones and then increases again to that of cyclohexanone in the large rings.6a In the benzocyclanone series, a decrease in the carbonyl frequency in passing from a-indanone to a-tetralone to a-suberone was observed by Lecomte.' On the other hand, Gutsche, while reporting a similar trend between the indanone I and the tetralone 11, detected no difference in the carbonyl frequency between I1 and the suberone III.s
0,I l 1
,/\,(CHz).
I,n = 0 11, n = 1
111, n = 2
The trend found by Lecomte has been confirmed (4) ( a ) 31. T. O'Shaughnessy and \V. H. Rodebush, ibid., 62, 2906 (1940); (b) W. 31. Schubert a n d H. K. Latourette, ibid., 74, 1829 ( 1952). ( 2 ) R . B. T u r n e r a n d D. I f . Voitle, ibid., 73,1103 (1951).
( 6 ) (a) V. Prelog, J . Cham. Soc., 420 (1950); (b) A. J. Birch, A n n . Repoiis, 104 (1951); (c) D. Biquard, BuZl. SOL. c h i ~ i . ,[j]7, 894 (1940). ( i )1. T,ecomte, .I. P h v c . K n d i w m , 6 , 257 (1945) (81 i' D. C.ut,che, T H I SJ O U R S A I , , 73,7 g i l9:l I
-4ug. 5 , 1955
NOTES
and has been found to extend to a-benzocyclooctanone (see Table 11). As shown in Table 11, the ring-size effect on the carbonyl frequency of the benzocyclanones closely parallels that for the cyclanones, if i t can be assumed that the “benzenering effect” is approximately the same for each of the benzocyclanones (i.e.,33 cm.-1).9
111-112° (2.4 mm.), n z 6 1.562810; ~ 1,2-benzocyclooctene1 - 0 n e - 3 ~(benzocyclooctanone), ~ b.p. 110-112° (2-20.5 mm.), w Z 5 ~1.5572lot”: cvcloDentanone.21 b.D. 128-130 : cvcloh e ~ a n o n e , ’b.p. ~ 1g2-i53”; cyclohep C=O) to a value less than l2Oo.l3 I t is possible that hydrogen crowding in the medium rings constrains the angle 0 to a value slightly greater than 120’. This would result in a slight increase in $-character (over the normal bond hybridization) to the carbon to oxygen valency. Consequently, the carbon to oxygen bond would be “looser,” and the vibrational frequency slightly lower than the “normal” value, that of cyclohexanone.14
Previous papers in this series‘ described partial hydrolysis products of methyltriethoxysilane and ethyltriethoxysilane. The former hydrolyzes much more readily than the latter, and a catalyst need not necessarily be employed. Methyltrimethoxysilane is hydrolyzed even more easily, as was shown recently by Kantor.2 m‘hen a benzene solution is stirred rapidly a t the boiling point in contact with three molar equivalents of water, with no added catalyst, virtually complete reaction occurs within 15 to 20 minutes. The hydrolysis products are entirely held in the lower, aqueous layer. Attempts to isolate crystalline or Experimental liquid intermediates of low molecular weight from Materials.-All the compounds used are known and were this water solution were unsuccessful. The prodprepared by known methods. I n the following list, the uct, a highly hydrated, high molecular weight reference given after the compound is to the source or “methyl T-gel” with only a very small proportion of method of preparation, and the reference given after the physical properties is to reported properties: acetophe- the original methoxy groups, can be represented none,15 b.p. 92” (21 mm.), nZ5D1.532016; o-methylacetopheempirically as [6(CH3)2Si203.10CH3Si(OH)O.HzO. none,” b.p. 84-85” (10.5 mm.), n Z 3 D1.53001’; 2,4-dimethyl- CH30H1,. This gel must have about 13 hydroxyls acetophenone,’* b.p. 118-120’ (32 mm.), c Z 41.533018; ~ 2,6-dimethyla~etophenone,~bb.p. 118-119 (32 rnm.), and 1 methoxyl for each 22 silicons. The large n Z 4 D 1.51464b; a ~ e t o m e s i t y l e n e ,b.p. ~ ~ 100-102” (7 mrn.), number of hydroxyl groups that this implies is in nZ5D 1.51554b; indanone-1,19 m.p. 39-40’; tetralone-1,lg agreement with the high water solubility of the b.p. 135” (20 mm.), n Z 5 1.566320; ~ benzosuberone,lO b.p. initial hydrolysis product.a Low molecular weight partial hydrolysis products (9) I n u-benzocyclooctanone, t h e least conjugated of these benzocyclanonw. t h e degree of resonance inhibition according t o ultraviolet can be isolated if half, or less than half, of the spectral d a t a appears t o be comparable t o t h a t in o-methylacctostoichiometric proportion of water is used. Under phenone. 1 h I l these circumstances, the initial reaction products (10) G . D. Hedden a n d W. G. Brown, THIS JOURNAL, 75, 3744 are found in the organic solvent, rather than in (1953). (11) W. bl. Schubert, W. A . Sweeney a n d H. K. L a t o u r e t t e , ibid., the water layer, and can be isolated by distillation 76, 5462 (1954). under vacuum. From a half-mole of methyltri(12) Measured b y S . L. Friess a n d P. E. Frankenberg, ibid., 74, methoxysilane and 1.5 molar equivalents (0.75 2679 (1952). mole) of water, there was obtained 9.2 g. of dis(13) Cf. L. J. Bellamy, “ T h e Infra-red S p e c t r a of Complex Molecules,” John Wiley a n d Sons, Inc., New Y o r k , N. Y . 1954, p. 128. tillable liquid. The predominant components of (14) According t o Fisher-Taylor-Hirschfelder models a n ” 0 - o u t ’ ’ this mixture are probably polycyclic, in the molecconformation for t h e benzocyclanones is highly favored over a n “ 0 - i n ” ular weight range of 400 to 600, and have 3 to 4 conformation. T h i s would appear t o rule o u t t h e explanation for t h e residual methoxy groups per molecule.l b The resiring-size effect once advanced b y Prelog,Ga namely, t h a t there is hydrogen bonding between t h e carbonyl oxygen a n d hydrogen a t o m s across due was a weak gel. t h e ring. The molar ratio of methyltrimethoxysilane to (15) Commercial. water then was reduced to 1:0.75. The crude reac(16) J . W. Bruhl, J . p r a k t . Chem., [2] SO, 131 (1894). tion product was refractionated carefully, and six (17) K. von Auwers, A n n . , 408, 242 (1915). (18) C. S. Marvel, J. H. Saunders a n d C. G. Overberger, THIS 68, 1085 (1946). (19) Kindly furnished b y D r . A. G . Anderson, J r . (20) Elsevier’s “Encyclopedia of Organic Chemistry,” Vol. 12B, Edited b y F . R a d t , Elsevier Publishing Co., Inc., Kew Y o r k , N. Y . ,
JOURNAL,
14.5r).
(1) (a) M. M. Sprung a n d F. 0. Guenther, THISJ O U R N A L , 77, 3990 (1955); (b) 77. 3996 (1955). ( 2 ) S. W. K a n t o r , ibid.,75, 2712 (1953). (3) T h i s product gives offwater freely on heating t o hiEher temperatures. Ultimately, a composition near t o t h a t of “methyl T-gel,” [(CHdzSiAI~l7,, is attained.
