Table Of ContentAROM ATIZATION STUDIES IN
THE NAPHTHALENE SERIES
A D issertatio n in Chemistry Presented
to the Faculty of the Graduate School of the U niversity
of Pennsylvania in P a rtia l Fulfillm ent of the Requirements
fo r the Degree of Doctor of Philosophy
uperviefor Chairman of Group Committee
A rthur Irwin Lowell
P hiladelphia, Pennsylvania
1951
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ACKNOWLEDGEMENT
This in v estig atio n was undertaken at the
suggestion of Dr. E. C. Horning. The author
wishes to take th is opportunity to express his
thanks to Dr. Horning fo r h is valuable advice
and assistance during the course of th is work.
Fellowships from the Research Corporation
and B risto l Laboratories are g ra te fu lly
acknowledged.
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TABLE OF CONTENTS
Page
Introduction . . . . .................................................................... 1
Discussion: Dehydrogenation ............................................... 3
D iscussion of Experimental .................................................... 15
Discussion: Spectra .......................................... ..................... 53
E x p erim en tal........................................................................................64
S u m m ary .........................................................................................................115
B ib lio g ra p h y ..............................................................................................116
B io g r a p h y .................................................................................. 120
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1
Introduction
During the past th irty years numerous examples of
the dehydrogenation of an a lic y c llc compound to an aromatic
compound have been reported. Many types of a lic y c llc
compounds undergo dehydrogenation under the appropriate
conditions, and th is general method has been used as a
route to many arom atic compounds. I ts chief use has been
fo r stru c tu ral purposes, i. e. to elucid ate the stru ctu re
of n atu rally occurring compounds. W ithin the past few
years i t has come into Increasing use as a p reparative
method to synthesize compounds in th e ir own rig h t or as a
supplement to i t s use in stru c tu ra l determ inations.
The work to be described in th is d iss e rta tio n
concerns the synthesis of certain su b stitu ted 3,4-dihydro-
naphthalenes and th e ir conversion to the re la te d naphthalenes
by c a ta ly tic dehydrogenation.
A series of 1,2,3,4-tetrahydronaphthaleneo were also
prepared by the reduction of the corresponding 3,4-dihydro-
naphthalenes.
Since several series of compounds were prepared vary
ing in type, number and location of su b stitu e n ts, and
degree of satu ratio n , the opportunity to study the effect
of these facto rs on the absorption of u ltra v io le t lig h t
was taken.
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2
The synthesis of several new 1-naphthols through
arom atlzation of the appropriately su b stitu ted 1-te tra lo n e s
was also attempted.
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3
Discussion: Dehydrogenation
The conversion of an a lic y c llc compound at the
same formal lev el of satu ratio n as an aromatic compound, or
a t a higher lev el, to an aromatic compound Is called
arom atizatlon.
A d e fin itio n of "aromatic character" Is based upon
th e number of p ro p erties which are common to arom atic
stru ctu res and whose possession gives the molecule th is
q u ality . These pro p erties may be used to define "aromat-
ic ity " , or they may be regarded as the m anifestations of
the nature of a stru ctu re which involves a ring system of
the benzene type. Of these p ro perties one of the most
fundamental is the unusual s ta b ility of the ring system
as compared with the s ta b ility in the lig h t of a lic y c llc
considerations. Thus benzene has le ss tendency to decompose
than the hypothetical a lic y c llc cyclohexatriene with non-
in te ra c tin g double bonds. This unusual Im m utability is
re fle c te d q u a lita tiv e ly in the thermal data fo r the com
bustion and hydrogenation of benzene and fo r the dehydro
genation of dihydrobenzene (when compared with the calculated
"alicy cllc" values).
There are numerous methods which can be used to convert
a lic y c llc compounds to aromatic compounds. They are de
pendent upon the stru ctu re of the a lic y c llc precursor.
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4
Isom erization has been used to effect the conversion
of a lic y c llc stru ctu res to th e ir aromatic Isomers. This
method 1b dependent upon the re la tiv e s ta b ility of the
two forms, and on the ease of tra n sitio n from one form to
the other. The aromatic form is usually more stab le. The
ease of tra n sitio n from one form to another u su ally d eter
mines the p o s s ib ility of separate existence of the a lic y c llc
molecule, esp ecially if the aromatic molecule is more stab le.
In some cases where an a lic y c llc compound is the intended
product, i t s aromatic Isomer Is obtained; the conditions
of the reaction induce isom erization. In other cases the
a lic y c llc compounds do have a separate existence and
isom eric arom atizatlon only awaits su itab le conditions.
A licycllc-arom atic isom erization u su ally can occur
through two general methods: (l) carbon-to-carbon fissio n
and (2 ) hydrogen re d istrib u tio n .
Carbon-to-carbon fissio n usually occurs in the tran s
form ation of stru ctu res with bridged rings to the arom atic
Isomer, and ring contraction and isom erization in other
cases, to mention a few examples.
An a lic y c llc compound can d iffe r from i t s arom atic
Isomer in the arrangement of hydrogen atoms alone. Isomer
iz a tio n In these cases requires only the re d istrib u tio n of
the hydrogen atoms so that the ring or rin g s acquire,
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5
through th is process, an amount of unsaturation correspond-
I
ing to the Kekule type of stru ctu re. Acids and bases,
hydrogenation c a ta ly sts, dehydrohalogenatlon, and heat have
been used to effect Isom erization of a lic y c llc compounds.
Dehydrogenation is another method which can be used
to convert an a lic y c llc compound to an aromatic compound.
The work described In th is d isse rta tio n concerns an in
v estig atio n of the synthesis of certain a lic y c llc com
pounds and th e ir conversion to arom atic compounds by the
removal of hydrogen.
During the past three decades, dehydrogenation has
been used mainly fo r stru c tu ra l studies of organic n atu ral
products. Notable early examples of i t s use in elu cidating
stru ctu re are in the polyterpene researches of Ruzicka (l)
and the dehydrogenation of cho lestero l and cholic acid
which played an Important part in determ ining the stru ctu re
of the ste ro ls (2). Haworth and Richardson (3), In th e ir
in v estig atio n s concerning the stru ctu re of podophyllotoxln,
converted podophyllotoxln into a compound containing the
1-phenylnaphthalene nucleus (I). They also prepared I by
an unambiguous method through dehydrogenation of the
lactone II.
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6
OcH,
OCH3
CH30 Or^^irOCi
IS O M . v
o ------------>
CHxOH
popopHyuuoroxiM P K R O P o p o PHYUIN
I
pd-black
ocH3 OCH,
ch^o^ \ , oc^ 3
pp-
oO QLftCK
X DEH YD RO P N H Y D R O -
P lcR O P o D O P H Y L L lU
The use of ordinary degradatlve methods to esta b lish
the stru ctu re of high m olecular weight a lic y c llc compounds
is d if f ic u lt and time consuming in many cases. The con
version of these compounds into re la te d arom atic compounds
by dehydrogenation answers the question of ring size and
p o sitio n , and p o sitio n of su b stitu en ts.
Dehydrogenatlon has come into increasing prominence
during the past few years as, a synthetic route to arom atic
compounds. This method is useful in many cases in stru c
tu ra l work, since the product of an unambiguous syn thetic
procedure may be compared with that obtained from a
degradatlve procedure. Bergmann and coworkers (4) synthe
sized arom atic reference compounds by dehydrogenatlon during
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7
th e ir in v estig atio n into the mechanism of the Wagner-
Jauregg reaction.
There are three reagents in preferred use at the
present time, su lfu r, selenium, and the platinum m etals.
The importance of su lfur in dehydrogenatlon was f i r s t
recognized “by Ruzlcka (1). Selenium was introduced by
D iels (5). Platinum and palladium in various forms are
also used. The use of palladium deposited on fin e ly
divided carbon is finding increasing favor.
Not very much is known about the reaction mechanism of
dehydrogenatlon. Any study of the mechanism of dehydro
genation with the several reagents used w ill have to
concern i t s e l f with accompanying thermal effe c ts since
dehydrogenations are usually carried out at re la tiv e ly
high tem peratures. The platinum metals are used as hydro
genation cataly sts; they have the a b ility to tra n sfe r
hydrogen from one organic molecule to another, or simply to
add and/or remove hydrogen from certain stru ctu res, with
or without the aid of m olecular hydrogen. This property
has been u tiliz e d for dehydrogenatlon purposes. Selenium
and su lfu r act on the a lic y c llc molecule in a way th at
the hydrogen is elim inated as hydrogen selenlde or hydrogen
su lfid e, as the case may be. Selenium has been reported
to have very slig h t a c tiv ity as a hydrogenation c ata ly st,
but according to P la ttn e r (6 ), c a ta ly tic dehydrogenations
are probably based on fundam entally d ifferen t reactio n s
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