Heterogeneous Catalysis - ACS Publications - American Chemical

7 Herman Pines and Organic Heterogeneous Catalysis

Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 3, 1983 | doi: 10.1021/bk-1983-0222.ch007

NORMAN E. HOFFMAN Marquette University, Todd Wehr Chemistry Building, Milwaukee, WI 53233

Herman Pines for over fifty years has made significant contributions to heterogeneous catalysis. He has emphasized hydrocarbon reactions. Among the areas he has researched are acid c a t a l y s i s , base c a t a l y s i s , aluminas, aromatization and dehydrogenation catalysts and metal hydrogenation catalysts. His students and colleagues over the years r e c a l l his i n d u s t r i a l and his academic career. I t may be best to begin with a very b r i e f sketch of Herman Pines' career i n organic heterogeneous c a t a l y s i s and then present a more d e t a i l e d review afterward. He began h i s career i n t h i s f i e l d over f i f t y years ago when he j o i n e d U n i v e r s a l O i l Products Company. In the e a r l y 1940 s, while s t i l l working f u l l time at u n i v e r s a l O i l Products, he j o i n e d the Northwestern U n i v e r s i t y f a c u l t y as a part time member, a s s i s t a n t p r o f e s s o r and a s s i s t a n t d i r e c t o r of the I p a t i e f f High Pressure and C a t a l y t i c Laboratory. Professor I p a t i e f f and he worked together at U n i v e r s a l O i l Products, and the P r o f e s s o r , as I p a t i e f f was c a l l e d by h i s coworkers and students, had already become a Northwestern f a c u l t y member. Pines considered I p a t i e f f h i s mentor. In the e a r l y 1950's Herman Pines resigned from h i s f u l l time p o s i t i o n o f Coordinator of E x p l o r a t o r y Research a t U n i v e r s a l O i l Products to become a f u l l time member of Northwestern s f a c u l t y . He was apointed V l a d i m i r I p a t i e f f Research Professor and D i r e c t o r of the I p a t i e f f High Pressure and C a t a l y t i c Laboratory. In 1970, he became V l a d i m i r I p a t i e f f Emeritus P r o f e s s o r . Thus, Herman Pines brought to an academic career a successf u l background i n i n d u s t r y and was able to help h i s students understand the i n d u s t r i a l s i g n i f i c a n c e of the chemistry they were l e a r n i n g i n the classroom and i n v e s t i g a t i n g i n the research l a b o r a t o r y . However, I do not want to l e a v e the impression that p r a c t i c a l i n d u s t r i a l research was being done i n the I p a t i e f f Laboratory. On the c o n t r a r y , the research was b a s i c , but o f t e n i t had i n d u s t r i a l i m p l i c a t i o n s . As h i s former students Joseph A r f

1

0097-6156/83/0222-0077$06.00/0 © 1983 American Chemical Society In Heterogeneous Catalysis; Davis, B., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


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HETEROGENEOUS

CATALYSIS

r i g o , Robert Kozlowski and Stanley Brown say, Herman Pines prepared h i s students w e l l f o r an i n d u s t r i a l career while c o l l a b o r a t i n g with them on b a s i c research problems. I would l i k e to r e t u r n to the e a r l y days a t U n i v e r s a l O i l Products. Herman Pines was earning h i s doctorate part time evenings and weekends at the U n i v e r s i t y of Chicago i n h i s f i r s t few years of working at U n i v e r s a l O i l Products. I o f t e n wondered how he was able to c a r r y that kind of workload. Among the chara c t e r i s t i c s that h i s former students l i k e Ralph Olberg, Jean Germain, and Alexander Edeleanu r e c a l l today were h i s energy and d e d i c a t i o n to chemistry. Surely these must have been p a r t of the answer. Herman Pines was organized too. Joseph Chenicek, who was a f u l l time graduate student at the U n i v e r s i t y of Chicago with Pines and who l a t e r a l s o j o i n e d U n i v e r s a l O i l Products, r e c a l l s that Pines would plan h i s experiments i n advance and, t h e r e f o r e , know the chemicals and s u p p l i e s he needed from the stockroom. He would ask Chenicek to o b t a i n them during the day so that Pines was able to work a t night and on weekends. In 1935 Herman Pines r e c e i v e d h i s doctorate presenting the graduate f a c u l t y with the d i s s e r t a t i o n e n t i t l e d "A Study of the E l e c t r o n e g a t i v i t i e s of Organic R a d i c a l s . " But p r i o r to w r i t i n g h i s d i s s e r t a t i o n he published h i s f i r s t paper (1). I t was a paper on the dehydration of butanol* Herman Pines' e a r l i e s t discovery i n a c i d c a t a l y s i s was what he and Prof e s s o r I p a t i e f f c a l l e d conjunct polymerization ( 2 ) . When low molecular weight o l e f i n s , f o r example, a butylène, are d i s s o l v e d Saturated Hydrocarbons b.p. up to 250°

Lower Layer i n c o l d s u l f u r i c a c i d , they produce on standing p a r a f f i n s and c y c l o p a r a f f i n s by hydrogen t r a n s f e r , and h i g h l y unsaturated hydrocarbons. T h i s work was t y p i c a l of the kind of research Herman Pines did at U n i v e r s a l O i l Products i n that he worked w i t h pure hydrocarbons to study a r e a c t i o n . His colleagues at U n i v e r s a l O i l Products, Herman Block, J u l i a n Mavity and Ralph Thompson remember that t h i s was always h i s approach. And that was i n c o n t r a s t to the use of petroleum f r a c t i o n s , which was t y p i c a l a t that time i n a petroleum research l a b o r a t o r y . But Herman Bloch notes that Pines was a b l e to e l u c i d a t e the b a s i c u n d e r l y i n g chemistry of hydrocarbons through working with pure compounds and many commercial processes stemmed d i r e c t l y or

In Heterogeneous Catalysis; Davis, B., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

7.

79

Herman Pines and Organic Catalysis

HOFFMAN

i n d i r e c t l y from h i s work. And one of these r e a c t i o n s was the a l k y l a t i o n o f i s o p a r a f f i n s and c y c l o p a r a f f i n s with o l e f i n s ( 3 ) . In 1932 Pines and I p a t i e f f d i s c o v e r e d the r e a c t i o n and i t con t i n u e s today, perhaps even more so, to be a t r u l y s i g n i f i c a n t petroleum r e f i n i n g r e a c t i o n . An example i s the a l k y l a t i o n of isobutane with ethylene to give 2,3-dimethylbutane. CH

3

CH--C-H


3

+

CH =CH 9

I C H

2

A

1

C

l

»

3

9

CHo-CH-CH-CH.

HC1

2

3

I

I

3

CH3CH3

3

It was t h i s kind o f r e a c t i o n that convinced Pines t h a t " p a r a f f i n " was a completely erroneous textbook d e s i g n a t i o n . To t h i s day he continues t h i s theme that alkanes and cycloalkanes are not without chemical a f f i n i t y . They react r e a d i l y under the proper c o n d i t i o n s . Another d i s c o v e r y was soon to f o l l o w f o r Pines and I p a t i e f f , the i s o m e r i z a t i o n of saturated hydrocarbons. Louis Schmerling, a colleague a t U n i v e r s a l O i l Products, r e c a l l s the day Pines awaited the Professor's a r r i v a l to t e l l him of t h e i r a n a l y t i c a l results. They had o b t a i n e d much isobutane from n_-butane. Schmerl i n e remembers that Pines' enthusiasm was so great i t was as though he was s a y i n g , "Eureka, we have i t l " This enthusiasm was t y p i c a l of h i s approach to research. H i s former students Herbert Appel and Donald LaZerte c a l l e d i t contagious. I t i s one o f t h e i r strongest memories of t h e i r student days with Herman Pines. In t h e i r i s o m e r i z a t i o n work Pines and I p a t i e f f found i t d i f f i c u l t to reproduce t h e i r r e s u l t s . Herman Pines s e t out to determine what the problem was. He and h i s a s s i s t a n t Richard Wackher d i d c a r e f u l experiments using high vacuum l i n e s f o r p u r i f i c a t i o n and i s o l a t i o n o f the r e a c t i o n from the atmosphere. They discovered pure η-butane was u n r e a c t i v e . Traces o f an o l e f i n were s u f f i c i e n t to cause r e a c t i o n L a t e r Pines and Wackher showed that a source of c a t i o n s was necessary f o r the i s o m e r i z a t i o n and oxygen, water or u l t r a v i o l e t r a d i a t i o n could produce cations (J>, 6). Pines, Block and Schmerling proposed the f o l l o w i n g mechanism (7)·

+ RCH=CH

2

+ RCHCH

3

+

+

+ CH3CHCH2CH3

HC1

+

AICI3

CH CH CH CH 3

2

2

3

CH*}

+

+ • CH3CHCH2CH3

3

+ • CH ÇHCH

> RCHCH3

2

T

C H

+ 3CCH

A1C1

+

4

RCHgCI^

3

CHQ


80

HETEROGENEOUS

+ CH CCH 3


CH

3

+

CH CH CH CH 2

2

2

3

* CH ÇHCH 3

3

+

CATALYSIS

+ CH CHCH CH 3

2

3

3

Here an o l e f i n i s the c a t i o n source. Formation of the c a t i o n i s the c h a i n i n i t i a t i o n step. The c h a i n i s propagated by carbocation a b s t r a c t i o n of an hydride from η-butane. S k e l e t a l rearrange ment occurs to form the more s t a b l e t e r t i a r y c a r b o c a t i o n . I'd l i k e to comment on the experimental methodology used to study the r e a c t i o n . Herman Bloch points out that Pines always was c a r e f u l and used the best a v a i l a b l e techniques to do h i s work. The use of high vacuum technique here i l l u s t r a t e s t h i s p o i n t . The i s o m e r i z a t i o n of cycloalkanes was f u l l y studied by s e v e r a l students c o l l a b o r a t i n g with Pines (8-17). Again they used high vacuum technique. And toward the end of t h i s research carbon 14 l a b e l i n g was done. Again, t h i s i l l u s t r a t e d Bloch's point: use of the best techniques. Herman Pines j o i n e d Professor I p a t i e f f at Northwestern Uni v e r s i t y at the time the I p a t i e f f Laboratory was being r e l o c a t e d from the basement of U n i v e r s i t y H a l l to the T e c h n o l o g i c a l I n s t i t u t e . Leon Gershbein, a student of I p a t i e f f and Pines at that time, r e c a l l s that Pines' thoughts and plans were c o n s t a n t l y with the new I p a t i e f f Laboratory. He was s u c c e s s f u l i n making i t one of a k i n d among u n i v e r s i t y chemistry l a b o r a t o r i e s through out the world. In the mid 1940's, Pines and I p a t i e f f began p u b l i s h i n g what was to become a long s e r i e s of papers i n the s t u d i e s of terpenes. In a d d i t i o n to o f f e r i n g i n t e r e s t i n g s t r u c t u r e s and o p t i c a l a c t i v i t y , L o u i s Schmerling b e l i e v e s the terpenes allowed Pines and I p a t i e f f to study r e a c t i o n s at Northwestern that were of l e s s i n t e r e s t to management a t U n i v e r s a l O i l Products. In 1956, Herman Pines received the F r i t z s c h e Award of the American Chemi c a l S o c i e t y f o r h i s research i n c a t a l y t i c and thermal r e a c t i o n s of terpenes. Herman Pines' f i r s t graduate student, Ralph Olberg, d i d h i s research i n the terpenes and r e c a l l s that Pines was always a h i g h l y motivating i n f l u e n c e on him. One of the things that Herman Pines d i d that was motivating was to v i s i t us i n the l a b o r a t o r y f r e q u e n t l y and ask us about our r e s u l t s and t a l k about future experiments. We r e a l i z e d he was very i n t e r e s t e d i n our work. Many of us i n f a c t sometimes got a l i t t l e concerned about it. Pines, i n h i s zest f o r chemical r e s u l t s would have one ex periment a f t e r another to add to what we'd done. And, when, a f t e r three, four, or f i v e years of work, we thought we would begin w r i t i n g our d i s s e r t a t i o n , he was ready to add more e x p e r i ments. Donald LaZerte r e c a l l s t h a t , when he was ready to w r i t e , Pines was planning to add a whole new problem to h i s work. Some how we managed to complete our work and s a t i s f y Pines' s c i e n t i f i c curiosity.


7.

HOFFMAN



1

81

In the l a t e 1940 s Herman Pines s t a r t e d teaching a course i n c a t a l y t i c organic chemistry. The course emphasized hydrocarbon r e a c t i o n s , but i t a l s o covered other r e a c t i o n s such as hydrogénation of f u n c t i o n a l groups, dehydration of a l c o h o l s , and dehydrogenation of primary and secondary a l c o h o l s . The course was designed f o r s e n i o r undergraduates and graduate students i n chemistry and chemical engineering. Pines would l e c t u r e on Wednesdays f o r two hours because he came to Northwestern only two days o f the week, Saturdays and Wednesdays. I r e c a l l from t a l k i n g to other students i n the course at that time that t h e i r f i r s t impressions were much l i k e mine. Here I was two minutes i n t o the f i r s t l e c t u r e that was going to l a s t two hours and Pines was speaking i n what he s t i l l c a l l s the i n t e r n a t i o n a l language of science, "broken E n g l i s h " . What had I gotten myself i n t o ? But by the time h a l f an hour had passed, I understood everything he was saying. I t was f o r most of us new and adventurous - a subject not found i n textbooks. Pines was an e x c e l l e n t teacher because of h i s i n t e r e s t i n and knowledge of the subject. He was e n e r g e t i c and e n t h u s i a s t i c i n h i s pres e n t a t i o n and we learned a great d e a l . There was a teaching l a b o r a t o r y a s s o c i a t e d w i t h the course. It was i n a room l o c a t e d next to the research l a b o r a t o r y . I'm not sure a t the time that we a l l appreciated the experience we were g e t t i n g i n that teaching l a b o r a t o r y . I t was the f i r s t teaching organic l a b o r a t o r y that most of us had where we were given a wrench and t o l d to go to work. We used batch apparatus, i n c l u d i n g d i f f e r e n t kinds of autoclaves and flow equipment at atmospheric and a l s o moderate pressure. We learned how to experiment with pressured l i q u i f i e d gases. I t was something unique that Northwestern o f f e r e d to chemistry students. There i s a s t o r y about the design of t h i s teaching l a b o r a tory that shows Herman Pines o c c a s i o n a l l y made mistakes too. George Czajkowski, an a s s i s t a n t to Pines and the P r o f e s s o r , r e c a l l s that he and Pines designed a system f o r c l e a n i n g batchtype autoclaves i n the teaching l a b o r a t o r y . One c o u l d blow water, steam, or a i r through a tube i n t o the i n v e r t e d autoclave by choice of v a l v e s . W e l l , a f t e r t h e i r system was i n s t a l l e d , Czajkowski found one morning t h a t water had run out of the a i r l i n e s i n t o t e s t equipment i n the Mechanical Engineering Department the n i g h t before, and by morning, water had been coming out of a i r l i n e s throughout the b u i l d i n g . Obviously, the autoclave c l e a n i n g design was not without flaws. Stanley Brown remembers how he chose Herman Pines as h i s research a d v i s o r . During t h e i r i n t e r v i e w , Pines t a l k e d to him f o r an hour about the wonders of c a t a l y t i c chemistry, e s c o r t e d him through the I p a t i e f f Laboratory, introduced him to a l l the workers, and loaded him down with dozens of r e p r i n t s . I t was t h i s k i n d of approach that enlarged the I p a t i e f f Laboratory group. By the l a t e f o r t i e s Pines and the Professor had a t t r a c t e d a good s i z e d group of graduate students and postdocs. I think we



82

HETEROGENEOUS

CATALYSIS

were pleased that we were l a r g e enough to have others to t a l k to about common research i n t e r e s t s and to conduct group seminars but not so l a r g e that we couldn't f r e q u e n t l y see our research a d v i s o r . Leon Gershbein and Jean Germain remember that Pines was never too busy to drop whatever he was doing to help a student. Herman Pines t r i e d to have each student b u i l d some piece of equipment to add to the research l a b o r a t o r y , f o r example, an ozonizer or a b o i l i n g p o i n t apparatus. We had e x c e l l e n t equipment, and we were able to get a great deal done. The l a b o r a t o r y got the l a t e s t equipment appropriate f o r the type of research i n the I p a t i e f f Laboratory. For example, the I p a t i e f f Laboratory had a gas chromatograph before most academic laboratories did. But the salesman who thought he could convince Herman Pines to buy equipment wasn't s u c c e s s f u l u s u a l l y . I r e c a l l two cases, a distillation column salesman who thought he could s e l l Pines a spinning band column and a salesman t r y i n g to s e l l an autoc l a v e . We got the s p i n n i n g band column and the a u t o c l a v e , but Pines convinced the manufacturers to give the equipment to the l a b o r a t o r y because they could say t h e i r equipment was being used i n the I p a t i e f f Laboratory. A l s o , p u b l i c a t i o n s showing our use of the equipment i n the "Experimental" s e c t i o n s would help advertise i t . In the l a s t year of the Professor's l i f e , Pines and he began doing research i n base c a t a l y z e d hydrocarbon r e a c t i o n s at Northwestern. A f t e r the P r o f e s s o r ' s death and a f t e r Pines l e f t U n i v e r s a l O i l Products, he devoted i n c r e a s i n g e f f o r t to these kinds of r e a c t i o n s . Among them was the i s o m e r i z a t i o n of o l e f i n s (18> 19). +

Na B~

+

RCH CH=CH 2

2

• BH +(R-CHCH=CH «

* RCH=CHCH ) N a

2

+

2

>RCH=CHCH + (RCH—CH~CH ) 3

2

Na

A strong base such as sodium-benzylsodium a b s t r a c t s a proton to produce an a l l y l i c carbanion. A c h a i n propagation f o l l o w s through the carbanion a b s t r a c t i n g a proton to produce the a l l y l i c intermediate and an isomerized o l e f i n . Limonene isomerizes but i t a l s o dehydrogenates to p-cymene (20).

+


+

7.


HOFFMAN

83

r


+ H

0

A geminal dimethyl group does not prevent a r o m a t i z a t i o n (21),

CH

CHo

3

CH + CH,

CH

0

Alkylbenzenes are a l k y l a t e d on b e n z y l i c carbons by o l e f i n s (22), CHo

,

^ \ / C H

• l^^Jl

+ R"Na

CH Na 2

+ CH =CH 2

2

O

2

Na

+

CH CH CH Na 2

2

CH •CH CH CH Na 2

2

Ho^CH/^CH^

2


4

2

2

Na

84

HETEROGENEOUS

CATALYSIS

Alkenes dimerize and oligomerize i n the presence o f strong bases (23). 2

+

B"

2

+

CH CH-CH -

CH CH=€H 3

CH CH»CH 2

•BH

3

CH CH»CH 2

2

CH «CHCH CHCH 2

2

2

CH CH *CHCH CHCH Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 3, 1983 | doi: 10.1021/bk-1983-0222.ch007

2

2

CH

+

2

CEjCH^CI^

2

0

• CH «CHCH CHCH 2

2

+

3

CI^CH-CI^

CHo

0

In the mechanism o f d i m e r i z a t i o n , an a l l y l i c carbanion i s formed and adds t o propylene so as to give the more s t a b l e primary i o n . Thus, the dimer i s branched. For almost every r e a c t i o n presented thus f a r - a c i d and base c a t a l y z e d - a mechanism was shown. The understanding o f a r e a c t ion i n terms o f i t s mechanism has always been a primary goal i n P i n e s research. F o r s e v e r a l of h i s students l i k e Eugene A r i s t o f f and Bozidar S t i p a n o v i c , h i s i n t e r e s t i n mechanisms i s one o f t h e i r strongest memories o f h i s research approach. Herbert Appel r e c a l l s that Pines taught him never to be s a t i s f i e d with a mechanism u n t i l i t e x p l a i n s a l l the products. Workers i n the I p a t i e f f Laboratory were always aware of the d i f f e r e n c e s i n a c t i v i t y , p a r t i c u l a r l y a c i d a c t i v i t y , of the s i l i c a and alumina they used. In the l a t e f i f t i e s and e a r l y s i x t i e s , Pines and h i s students studied the i n t r i n s i c a c i d i t y and c a t a l y t i c a c t i v i t y o f aluminas as a f u n c t i o n of t h e i r p r e p a r a t i o n method (24). They i n v e s t i g a t e d the dehydration o f a l c o h o l s (25-31) and many e x c e l l e n t papers were c o n t r i b u t e d i n the alumina area and i n the area o f alumina supported dehydrogénation and aromatization c a t a l y s t s (32, 33, 34). In the e a r l y f i f t i e s , Pines and I p a t i e f f s t u d i e d a very usef u l s y n t h e t i c r e a c t i o n , r e d u c t i v e dehydroxymethylation o f primary a l c o h o l s (35, 36, 37). 1

2H

2

+

Ni

RCH OH

•

2

RH

RCH OH 4 = ± RCHO 2

RCHO CO

1

3H

0

RH

+

-f CH/.

+

+

CH^

+

H0 2

^

CO H 0 2

Pines, i n pursuing t h i s r e a c t i o n , found that running the r e a c t i o n i n the presence of thiophene o r methyl s u l f i d e gave o n l y reduct i v e dehydroxylation of a primary a l c o h o l (34).


7.


HOFFMAN

85

Cl^CIL^CH^ Ni RS 2

RS

thiophene or methyl


2

sulfide

When an a l c o h o l prone to rearrange i n the presence of a c i d s was used, rearrangement occurred i n the presence of s u l f u r but not i n i t s absence. 3,3-Dimethyl-l-butanol gives neopentane when s u l f u r i s absent but s u b s t a n t i a l amounts of 2,3-dimethylbutane when s u l f u r i s present. C C-C-C

Ni

C-C-C-C-OH

N

1

>

*2

S

» C-C-C-C

+

I

ι

C-C-C-C

c c

c

C The l a t t e r compound was b e l i e v e d to be formed by dehydration and a c i d c a t a l y z e d rearrangement p r i o r to hydrogénation. A f u r t h e r extension of the n i c k e l s t u d i e s was the observat i o n that n i c k e l c o n t a i n i n g n i c k e l oxide could be used as a c a t a l y s t f o r ether formation (39-49). Herman Pines viewed t h i s as a concerted dehydration. R-CH ^^0-CH -R 9

9

RCH OCH R 2

2

+

H0 2

L \ The r e a c t i o n was i n v e s t i g a t e d u s i n g other metals, platinum, p a l ladium, i r i d i u m , and rhodium (50, 51). A sketch of Herman Pines would not be complete without reviewing some of h i s awards. A f t e r the A. C. S. F r i t z s c h e Award, Herman Pines r e c e i v e d the Midwest Award of the St. L o u i s S e c t i o n of the American Chemical S o c i e t y i n 1963. In 1981 he r e c e i v e d the American Chemical S o c i e t y Award i n Petroleum Chemistry. In 1981 he a l s o r e c e i v e d the Eugene J . Houdry Award i n A p p l i e d C a t a l y s i s of the C a t a l y s i s S o c i e t y . At i t s recent meeting i n Las Vegas, he r e c e i v e d the 1982 Chemical Pioneer Award of the American I n s t i t u t e of Chemists. Space l i m i t a t i o n s prevent e l a b o r a t i o n of a l l of h i s honors. But I do have enough space to g i v e you perceptions o f him by h i s students and c o l l e a g u e s i n a d d i t i o n to those already mentioned. Herman Pines took a personal i n t e r e s t i n the progress and w e l l being of each of h i s students. For example, more than one of them needed more f i n a n c i a l help at times than was a v a i l a b l e through t h e i r graduate student s t i p e n d s . Herman Pines found sources who were w i l l i n g to pay f o r p r e p a r a t i v e o r g a n i c work, and



86

HETEROGENEOUS CATALYSIS

the student overcame h i s f i n a n c i a l d i f f i c u l t y by doing some organic preps. He counseled students when they were f i n i s h i n g t h e i r graduate o r p o s t d o c t o r a l work and seeking an employer. He helped h i s students i n academic c a r e e r s t o get t h e i r names i n p r i n t by coauthoring books and chapters i n books with them. He was always s o f t spoken. We never saw him angry. He was genuinely frank and never m a l i c i o u s l y took apart a c o l l e a g u e . We a l l enjoyed h i s good sense o f humor. Herman Pines i s s t i l l c o n t r i b u t i n g to the chemical l i t e r a t u r e ; I'm sure he w i l l p u b l i s h many more papers.

Literature Cited

1. Pines, H. J. Am. Chem. Soc. 1933, 55, 3892 2. Ipatieff, V. N.; Pines, H. J. Org. Chem. 1936, 1, 464. 3. Ipatieff, V. N.; Grosse, V.; Pines, H.; Komarewsky, V. I. J. Am. Chem. Soc. 1936, 58, 913. 4. Pines, H.; Wackher, R. C. J. Am. Chem. Soc. 1946, 68, 595. 5. Pines, H.; Wackher, R. C. J. Am. Chem. Soc. 1946, 68, 599. 6. Wackher, R. C . ; Pines, H. J. Am. Chem. Soc. 1946, 68, 1642. 7. Bloch, H. S.; Pines, H.; Schmerling, L. J. Am.Chem.Soc. 1946, 68, 153. 8. Pines, H.; Abraham, Β. M.; Ipatieff, V. N. J. Am. Chem. Soc. 1948, 70, 1742. 9. Pines, H.; Aristoff, E . ; Ipatieff, V. N. J. Am. Chem. Soc. 1949, 71, 749. 10. Pines, H.; Aristoff, E . ; Ipatieff, V. N. J. Am. Chem. Soc. 1950, 72, 4055. 11. Pines, H . ; Aristoff, E . ; Ipatieff, V. N. J. Am. Chem. Soc. 1950, 72, 4304. 12. Pines, H.; Pavlik, F. J.; Ipatieff, V. N. J. Am. Chem. Soc. 1951, 73, 5738. 13. Pines, H.; Pavlik, F. J.; Ipatieff, V. N. J. Am. Chem. Soc. 1952, 74, 5544. 14. Pines, H.; Huntsman, W. D.; Ipatieff, V. N. J. Am. Chem. Soc. 1953, 75, 2315. 15. Pines, H.; Aristoff, E . ; Ipatieff, V. N. J. Am. Chem. Soc. 1953, 75, 4775. 16. Pines, H.; Myerholtz, R. F., J r . ; Neumann, H. M. J. Am. Chem. Soc. 1955, 77, 3399. 17. Pines, H.; Myerholtz, R. W., Jr. J. Am. Chem. Soc. 1955, 77, 5392. 18. Pines, H.; Vesely, J. Α.; Ipatieff, V. N. J. Am. Chem. Soc. 1955, 77, 347. 19. Pines, H.; Haag, W. O. J. Org. Chem. 1958, 23, 328. 20. Pines, H.; Eschinazi, H. E. J. Am. Chem. Soc. 1955, 77, 6314. 21. Pines, H.; Eschinazi, H. E. J. Am. Chem. Soc. 1956, 78, 5950. 22. Pines, H.; Vesely, J. Α.; Ipatieff, V. N. J. Am. Chem. Soc. 1955, 77, 554. 23. Mark, V.; Pines, H. J. Am. Chem. Soc. 1956, 78, 5946.


7. HOFFMAN Herman Pines and Organic Catalysis


24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51.

87

Pines, H.; Haag, W. O. J. Am. Chem. Soc. 1960, 82, 2471. Pines, H.; Haag, W. O. J. Am. Chem. Soc. 1961, 83, 2847. Pines, H.; Manassen, J . Adv. Catal. 1966, 16, 49. Blanc, E. J.; Pines, H. J. Org. Chem. 1968, 33, 2035. Pines, H . ; P i l l a i , C. N. J. Am. Chem. Soc. 1961, 83, 3270. Schappell, F. G.; Pines, H. J. Org. Chem. 1966, 31, 1735. Watanabe, K.; P i l l a i , C. N.; Pines, H. J. Am. Chem. Soc. 1962, 84, 3932. Pines, H.; Brown, S. M. J . Catal. 1971, 20. Pines, H.; Chen, C. T. J . Am. Chem. Soc. 1960, 82, 3562. Pines, H . ; Csicsery, S. M. J. Am. Chem. Soc. 1962, 84, 292. Pines, H.; Goetschel, C. T. J . Catal. 1966, 6, 371. Ipatieff, V. N.; Czajkowski, G. J.; Pines, H. J. Am. Chem. Soc. 1951, 73, 4098. Pines, H.; Rodenberg. H. G.; Ipatieff, V. N. J . Am. Chem. Soc. 1953, 75, 6065. Pines, H.; Rodenberg, H. G.; Ipatieff, V. N. J . Am. Chem. Soc. 1954, 76, 771. Pines, H.; Shamaiengar, M.; Postl, W. J. J. Am. Chem. Soc. 1955, 77, 5099. Pines, H.; Steingaszner, P. J . Catal. 1968, 10, 60. Pines, H. and Kobylinski, T. P., J . Catal. 1970, 17, 375. Kobylinski, T. P.; Pines, H.; J . Catal. 1970, 17, 384. Pines, H.; Kobylinski, T. P. J . Catal. 1970, 17, 394. Hensel, J.; Pines, H. J. Catal. 1972, 24, 197. Pines, H . ; Hensel, J.; Simonik, J. J. Catal. 1972, 24, 206. Simonik, J.; Pines, H. J. Catal. 1972, 24, 211. Pines, H.; Simonik, J . J . Catal. 1972, 24, 220. Licht, E . ; Schachter, Y.; Pines, H. J. Catal. 1973, 31, 110. Licht, E . ; Schachter, Y.; Pines, H.; J . Catal. 1974, 34, 338. Licht, E . ; Schachter, Y.; Pines, H. J. Catal. 1975, 38, 423. Licht, E . ; Schachter, Y.; Pines, H. J. Catal. 1978, 55, 191. Licht, E . ; Schachter, Y.; Pines, H. J. Catal. 1980, 61, 109.

Received November 10, 1982


Heterogeneous Catalysis - ACS Publications - American Chemical

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