NOKTJXWESTERX UNIVERSXTY
   COLLEGE OF LIBERAL ARTS
        LTANSTON, lWLMOfS

DEPARTMENT OF CHEXISTRY

frovember 29, 3.939

Dr, KiChael Xeidelberger,
College of Z'hysicians t;nd Surgeons,
C oldmbi 6. Gnive-r 8 it y ,  B o Y ,

DeEr Dr. Seidelbereer:

Kv:y delay in answering your letter of the 8th h6s not been

cause8 from lack of interest, I Essure you. ?he& you for
writing me.

dme. ',:%et is more, it reads convincinglyrbut it does seem to me
thst %?e argument has loop-holes, eorne of which I mentioned in
the paper.

OCt&

I agree viith you that the work on cyclotetraene was chrefully

The nerrow boiling rarge (0.5") vhich 301.1 mentiortea cerinot

be lealed on too heavily for isosfieric dibronides should 'coil
pretty cloeel;7 together.

YOU mentidn th&t different effects might hizve been encountered
at pyrolysis tem'neratures of 2CO-25O0 than at 100-150O. Perhaps
so, hit I doubt it bemuse no co:ayrable rearrangements occur
with other unsatcra ted hyd-socarbons till much higher temperatures
&re reacheij. l-3utene is fairly stsble et 500°, and rearrLrigement
in%o 2-butene etsts i;it 6OC-65O0 (Ewd end. Soldsby, J. An. Chem.
GOC., 56, 1813 (15b4)). Similarly, GCCO is tine tempemiture re-
quired to initiate the reerrargwent of 1- into 2-pentene fmrd,
Goodyear, ad GolCisb;r, ibid., $8, 235 (1cJS6) 1. Resrraneement of
1-alkynes into 1,Z-alkadienes does not occur at 400°, 'nzt requires
tezTeratures v;hich we high enough to break the hydrocarbon other-
mise int:, smeller molecules ('iurd @id Christ, ibid, , s, 22G1
(1937) 1. L'hese nere experiments v:ith l-heptyne, I-hexTDe and 1-
bu?;:Qne. 's':ith the butyne, it w&s proven that no 1,2~-but&diene came
even at 56C". Hence I feol th8t anphere between 1@C-500* would.
he sife ternperbturee insofar subsequal rearranpez-ients tire
concermd v.hen dehl in2 aith 1 ,%-butsi3iene, 1,3-Futadiene, or
1- or 2-butyne.

You point out thst our X we.s F,. 1,2-diquaternary compound
riherecs Sillstatter's VI1 (in our paper) w8s not. That is E? good
criticism snd one thst I hed thought of. liothing would be gained
by taking the l,4-isomer that you sugcester? , however, nb.liely,
Y@I~,t'Ie:,-C';ZC;i~C--2CS2T?":e30E, because 1,3-butadiene is the only

possibility here. If the C6-&nelog were taken, CH3 f EflN "--2 CB ,F"c"51

I feel sure it would pyrolyze to the fAxture of 1,5-, 1,4-, cnd
2,r-hexadienes the last of which is the only conjugated one. of

me 3 c E  NI'% 3 0 E

2.

course this mixture would involve greater analytictiil difficulties
than the Cq- analogs. J-lso, the oriyiml synthesis v~c~uld be harder.

There is one experiment more convincing than rzny of these that

I woulir like to have triecl, nbmely, the ~yrolpis of CH$H-CH=CH2.

T?i&b$ae double bond already in place this Rould be quite anelopouE
to Tillstatter's VII. Tlie difficulty here is the fcct thgt the ha-
lide, CH5CIlBrCB=CH2, from whibh the hydroxide would be mbde ig SO

unstable gieliiine CH3CB=CHCYZ2r. 2be base correEpondicg to t; e

lstter should pyrolyze exclusively to methylallene, xhereas %'in
desired isomer niight pyrolyze either -to methylallene or 1 ,Z-buta-
diene, 2he experiment, ti herefore, would be inconclusive.

TKe3OY

  ?he best excape from this dilemma, and it is an experiment I
have planneir to do for a 10s time, is to take the Cg-anelog.
If CH3CHBrCE=CHCH3 reerrenges, the product is still the seme corn-

pound. Hence the bwe, CB3CH(~~~:e30H)-CH=CHCHB, ehoulZl be g'otainable
pure. It should yield either 1,3- or 2,2-yentadienet or both. A
mixture of the two pentadienes could be sepw'ated by mems of
maleic anayciride, so the approach seems fairly definite.

I shall F-e pleased to kee? you advise3 of further developments.

'Thank jrou ever SQ much for jrour he1pfu.l suggestions.

Very sincerely yours,

f?fud& au

Charles D. Hurd