ROBERTBURNSWOODWARD
72
deposited (IX) in black needles on cooling. When crystallized from butyl acetate the compound Ix melts at 255’. With cold concentrated sulfuric acid the compound gives a red-violet color; on heating a change to blue-violet, rose and finally yellowish-green occurs. dnal. Calcd. for c ~ ~ H C, ~ ~91.1; o : H, 4.7, ~ ~
C, 91.2; H, 4.9. cy-
Summary (4Phenanthryl) - cy, P-diphenylethanol yields
[CONTRIBUTION FROM THE CONVERSE
Vol. 64
two geometrically isomeric ethylenes upon dehydration. the of alkali metal to these isomers two sterically different metal-organic compounds are formed. A probable steric formula is ascribed ~ ~ to deach :of the two “stilbenylphenanthrenes” based upon the products of the alkali metal addition reaction. REHOVOTH, PALESTINE
RECEIVED FEBRUARY io, 1941
MEMORIALL A ~ O R A T OOF RY HARVARD UNIVERSITY]
Structure and Absorption Spectra. 111. Normal Conjugated Dienes BY ROBERTBURNSWOODWARD It is now clearly recognized’ that the conju- type, e. g., 1,l’-dicyclohexenyl (Table I, comgated diene chromophore may manifest absorp- pound 6) and 2-hydroxy-a, P-dicyclohexylidenetion in one of two broad regions, according to ethane (Table I, compound 7) have different whether the two double bonds comprising the ab- values of A,,,,, while in other cases compounds of sorbing system are or are not present in a single different substitution type, e. g., allylidenecycloring. The former class as a whole absorbs suffi- hexane (Table 11, compound 4) and zingiberene ciently far to the red (255-290 mp) to necessitate (Table 11, compound 6 ) have identical maxima. the postulation of a first order environmental ’These facts indicate clearly that one or more posieffect, comparable in magnitude with the linear tional factors are superimposed upon the expected introduction of an additional double bond.2 The substitutive effect. The nature of this positional factor is discernsecond class, however, may be considered normal, and the variations (215-250 mp) within the group ible without difficulty. It has been5 pointed out are certainly the result of second order environ- that the introduction of strain into a given chromental effects similar to those discussed in con- mophore will labilize the electronic system with nection with a$-unsaturated ketones in the first a consequent shift toward the red of the absorppaper of this ~ e r i e s . ~This communication is tion band associated with the system. It is well concerned with the substitution-type classifica- known that a double bond exocyclic to a sixtion of these normal diene^.^ membered ring is unstable by ca. 3.5 k. c. with Inspection of the position of the band maxima respect to the corresponding endocyclic comfor a number of dienes reveals immediately that pound.6 Further evidence of the strained charsimple substitutive effects cannot be the sole fac- acter of such bonds may be found in the very tor in causing variations within the group, since high reactivity of cyclohexanone, and in the in some cases dienes of the same substitution equilibrium data for systems of the type AIcyclohexenyl-1-acetic acid cyclohexylidene(1) Fieser and Campbell, THIS JOURNAL, 60, 160 (1938), Bergmanu and Hirschmann, J Org. C k m , 4, 40 (1939), Callow, -7 acetic acid.7 It is therefore reZonab1e to assume Chem. Soc., 462 (1936). that a diene chromophore Containing such 62x0(2) Possibly the electrons of the single bond which is a,8 to each of the double bonds of the diene chromophore are sufficiently labilized cyclic linkages absorb nearer the red than to permit oscillations approximating those of a conventional the corresponding system lacking such linkages, but of the same substitution type. . In actual fact, this assumption is amply justified. Table I lists the symmetrical dienes* of electron system such as that of the trienes. (3) Woodward, THIS JOURNAL, 63, 1123 (1941). known structure whose absorption characteristics (4) Booker, Evans and Gillam, J. Chem. Sor , 1453 (1940),in
*
91%-
an encellent paper containing valuable new data have classified dienes into several groups, e . g., acyclic, acyclic with a cyclic substituent, pemicyclic, bicyclic, etc. It will be evident from the sequel that the presence or absence of a ring in a normal diene has no intrinsic effect on the position of k-.. except in so far as the structure is such that the ring exert$ a normal substitutive or positional effect.
(5) Lewis and Calvin, Chem. Rev., 2.5, 273 (1939). (6) Cf. Hiickel, “Theoretische Grundlagen der organischen Chemie,” 2nd edition, p. 72. (7) Iinstead, J . Chem. S O L ,1603 (1930). (8) I . e . , symmetrical in so far as the substitutive and positional factors about the double bonds are concerned.
ABSORPTION SPECTRA OF NORMAL CONJUGATED DIENES
Jan., 1942
73
TABLE I Formula
Substance
Xmt.,,(calcd.)
..
217 mp 226
227 227 227
227 228 228
237
236
247
248
247
245
247
247
247
246
Cholestadienol D-acetate'
247
245
Cholestadienol Ba-acetate!
247
246
A%4-HexadieneC 1,6-Diacetoxy-A294-hexadienec 1,6-Diethoxy-A2)4-hexadienec 1,1-Dicyclohexenylc
CHz=CH-CH=CHz CH~=C-C=CHZ
Xmsx,(obs.)
227 mp
Butadiene" B,r-Dimethylbutadieneb
I
1
CH3 CH, CH3-CH=CH-CH=CH-CH3 AcOCHp-CH=CH-CH=CH-CHzOAc
EtOCH2-CH=CH-CH=CH-CHzOEt 1
AH*(CHZ)~CH=C-&=CH(CHZ)~HZ 1
2-Hydroxy-a, 6-dicyclohexylideneethaned
7
1
HO--dH( CHZ)~C=CH-CH=C( CHz)dCHz
-
r----7
2,5-Dihydroxy-2-methyl-a,~-dicyclo-HO--~(CH~)~&=CH-CH=C(CH~)~CH~ I hexylideneethane" CHI 2,5-Dihydroxy-a,B-dicyclohexylideneethane-2-acetic acids
HO-C( CH2)2CHCHzC=CH-CH=C(
I
HOOC-CHz
I
r
i
CHz)aCHz
OH , HO-C( CH&CHCHzC=CH-CH=&( CH2)aCHz I
S-Hydroxy-6-acetoxy-a,P-dicyclohexylideneethane-2-acetic acide
I
HOOC-CHz
I
OAC
Smakula, Angew. Chem., 47, 657 (1937). * Scheibe, Ber., 59, 1333 (1926). e Booker, Evans and Gillam, J . Chem. Soc., 1453 (1940). Dimroth and Jonssen, Ber., 71,2658 (1938). e Aldersley, Burkhardt, Gillam and Hindley, J , Chem. Soc., 10 (1940). Windaus, Linsert and Eckhardt, Ann., 481, 119 (1938).
'
with the a$-unsaturated carbonyl system a diene have been determined. The values of A,, (calcd.) were obtained by adding to the base containing two double bonds, a! and p, may be value (butadiene, Amax. = 217 mp) 5 mp for each considered as a composite of the type substituent, and 5 mp for each exocyclic bond present in the diene system. It will be seen that the agreement is in every case excellent. The shift (AX, = 5 nw) accompanying the introduction of a single substituent into a conju- where U, and U, correspond to the carbonyl gated diene system seems a t first thought very low group. The position of Amax. for the two comin comparison with the shiftg (AX, = 10-11 mp) ponents will be XO nI Ah, XO +nII AX, and Amax. in the a,P-unsaturated carbonyl system. Since, for an actual diene will be the average of the comhowever, this displacement is actually 5 mp for ponent values. lo For 1,l'-dicyclohexenyl (Table the whole diene system, the actual shift, referred I, compound 6 ) , nI = nII = 2, Amax, = 236 mp, to one carbon-carbon bond, is 10 mpJi. e., the sub- whence AA = 10 mp, stitutive effect is almost identical in the two sysWe now turn to the unsymmetrical dienes, listed tems. This point may be clarified by the follow- in Table 11. Under A, and A,, are listed the ing example. In order to effect a comparison (10) I t will be evident from the sequel that this m a y be rigidly
+
(9) Woodward, THIS JOURNAL, 63, 76 (1941).
true only in symmetrical case.
ROBERTBARNSWOODWARD
i4
Vol. 64
'TABLE 11
Substance
Formula
Piperyleneu
ii
Isopreneb
-k M B ) / z 222
217 227
222
220
217 227
222
224.5
217 247
232
236.5
217 247
232
236
227 23;
232
235.5
217 237
227
230
227 237
232
242
227 237
232
235
227 237
232
232
217 247
232
233
237 247
242
236i
227 247
237
235
237 247
242
240
237 247
242
240
227 247
237
238
242k 247
248
X@b
Xmax. (obs.), mr
223.5
0
CHz=C-CH-CH? a
81
CH3 CH~=C-CHZCH~ B
Myrcene"
217 227
XQO
CHsCH=CH-CH=CH*
CH~CH~CH=C( CH~)? r---i
.4llylidene-cyclohexanea
CHdCH&C=CH-CH=CH2 i3
(1
d2-Uirnethyl(CH,,,NCH,CH!CH,~,~=CH-CH=CH~ A aminomethyla cyclohexy1idene)- &-propene'
_---_
___1
CHXH=C(CH~)~CHCHCH=CH-CH=C(CH,:, u B
Zingiberenea
CH3
CHI
r
-
A'-Cyclohexenyl ethylene"
1
CHZ(CH2)3CH=C-CH=CH2 B
c*
CH,
A3~8(g)-nor-Men- CHz(CH&CH=C-C=CH2 R a thadiene" CHJ r CHICHZCHCH~CH=C-C=CH,
Menthadiene"
a
1
CH,
2-Methyl- A1cyclohexenyla ethylene
&Hz(CH~:~C=C-CH-CHI
IB
CHI I
A, 2
7-Methylenecholesterold
I
HO/'d&'
l
l
'bCH,
AsPb-Cholestadieneo Testosterone diacetate# Cholestenone enolacetat@
I 1 1
,I
1
AcO/
$d& )
R I
9-Oxycholestadienol'
227
257k 267
AESORPTIONSPECTRA OF NORMAL CONJUGATED DIENES
Jan., 1942
TABLE I1 (Concluded) Substance
Formula
Xaa
(Xaa
237 247
Abietic acidf
+ X&9)/2
95 Xmax. (obs.), mp
242
237.5
’
a Booker, Evans and Gillam, J . Chem. SOL.,1453 (1940). Scheibe and Pummerer, Ber., 60,2163 (1927). Milas and JOURNAL, 61,2534 (1939). Bann, Heilbron and Spring, J. Chem. Soc., 1274 (1936). e Stavely and BergAlderson, THIS mann, J. Org. Chem., 1,567 (1937); Bergmann and Hirschmann, ibid., 4, 40 (1939). Kraft, Ann., 520, 133 (1935). Westphal, Ber., 70, 2128 (1937). Dane, Wang and Schulte, Z. physiol. Chem., 245, 80 (1937). Windaus and Zuhlsdorff, Ann., 536, 204 (1938). No curve given; inflection (?) reported. Ir This case brings up the important point of the effect of a double bond exocyclic to afioe-memberedring. From the meager data available it is not possible to estimate this effect.
’
’
’
calculated values of Amax. for the symmetrical dienes corresponding to the double bonds a and p 01 I I1 I11 (as marked). In all cases except that of A3,8(9)nor-menthadiene, A,, >Ama,, >Aaa, and, in fact, with the absorption data, but receives support the position of Amax,, except in this one case, is from the fact that preparations of menthadiene within 5 mp (average deviation 3 mp) of the aver- itself (11) usually contain appreciable amounts A,,)/2. It will be recognized that of A2,4(8) age (Aaa -menthadiene (I1I).l1 We are a t present this latter value for any diene is identical with that endeavoring to furnish a proof of this assumption which would be obtained by calculating A,,,, as in order to provide further evidence of the power was done in the case of the symmetrical dienes. of the absorption method in the determination of However the unsymmetrical dienes, have been structure. considered in this way, i. e., as composite systems Summary intermediate between two symmetrical systems, since it is not possible a t present to determine I t has been shown that by the use of simple whether the small discrepancies in A,, . (calcd.) substitutive and positional shifts it is possible to are due to experimental variations, or whether, calculate with reasonable accuracy the position of as is quite possible, subtle constitutive factors the band maxima in the absorption spectra of shift the maximum slightly toward that charac- normal conjugated dienes, i. e., those dienes which teristic of one or the other of the component sys- do not contain both double bonds within a single tems. ring. The most probable explanation of the apparThe use of these generalizations in structure ently anomalous behavior of A3’8(9)-nw-mentha- determinations is exemplified, and certain analodiene is that the structure a t present assigned to gies between the diene chromophore and the g,@this compound is incorrect. It is reasonable to unsaturated ketone chromophore are pointed out. assume that the substance is actually largely CAMBRIDGE, MASS. RECEIVED SEPTEMBER 18, 1981 A294(8)-nor-menthadiene(I), for which A,, = (11) Indeed, the sample of I1 used by Booker, Evaus and Gillam 257 mp,A, = 227 mp, (Aaa XB,)/2 = 242 (ref. 4) in the determination of the absorption spectrum was described mp, a view which not only is in excellent accord as probably containing 23% of the isomer 111.
+
+
