Sulfur in Petroleum Nomenclature of the Sulfur Compounds in P e t r o l e u m JOHN
S.
B A L L AM>
\\ . E. 11
VINES,
X HI-; need for reform in noineiichtture of organic compouml.s has become very evident d u r i n g the past decade. In this period m a n y new compounds, some similar to those previously known a n d others radically different, have been discovered. S y s t e m s of nomenclature that met t h e needs a d e q u a t e l y a few years ago have b e come obsolete by the discovery of new compounds. Tin* B u r e a u of Mines, in a long-range program designed to furnish fundamental d a t a o n t h e sulfur compounds of petroleum, h a s h a d as one project the compilation of t a b l e s of physieal properties of sulfur c o m p o u n d s . The compilation of these tables, with the resultant research in t h e literature, b u s brought to light many ins t a n c e s of confusion in naming compounds. Not only a r e several systems in vogue, but n u m e r o u s combinations of these systems have been used with the resulting formation of h y b r i d systems. This discussion is being p r e s e n t e d hot}- from t h e point of view of giving information to enable interpretation of the various names a n d also as a plea for systemization of t h e nomenclature. T h e requirements of a good system of n o m e n c l a t u r e m a y be listed a s : 1. T h e system of n a m i n g should conform a s far a s possible to p r e s e n t usage. 2. T h e resulting n a m e s of individual c o m p o u n d s should indicate t h e group of c o m p o u n d s t o which the individual b e longs. 3. T h e system should be applicable t o all c o m p o u n d s which fall within t h e scope of t h e group being n a m e d . 4. T h e resulting name of each compound m u s t be definitive. o. T h e compound n a m e should be as simple a n d usable as possible.
Petroleum and Oil-Sliale Experiment Station, Bureau of Mines, Laramie, W y o . buch dor organischen Chemie". The variations among these t h r e e sources are sufficient to be confusing. Investigation of t h e sulfur compounds of petroleum h a s not proceeded far enough to permit a definite s t a t e m e n t a s to which sulfur compounds occur in petroleum. In the large sense, one might s a y t h a t all compounds of carbon, hydrogen, and sulfur are possible. However, t h i s m a y be limited considerably by the assumption that, since most petroleums contain relatively small percentages of sulfur, very few compounds containing more t h a n one sulfur atom to t h e molecule will be found. If we limit the group further b y excluding such reactive compounds as thioaldohyclos and thioketnnes, t h e groups of compounds remaining a r e thiols ( m e r c a p t a n s ) , sulfides, and thiophene and its homologs. ft is recognized t h a t these limitations a r e ex-
11
Presented by permission of the Director, Bureau of Mines, U. S. Department of the Interior. V O L U M E
2 4,
NO.
Ethyl mercaptan
IT—C—C—S—II I
1
II
It H 1
ji—c*=a—c—s— ii II
IL
N a m e s b y V a r i o u s M e t h o d s ; of N o m e n c l a t u r e International Mercapto Sulfhydryl Union Thiophenol system system system system SulfhydrylMercapto— Ethanethiol" e thane ethane
Allyl mercaptan
2-Propene-lthiol"
Phenyl mercaptan
Benzenethiol"
P-Tolyl mercaptan
/j-Toluenethiol" (4methyl-1benzene thiol)
Cyclopentyl mercaptan
ii
H II—C
C—S—11 C—IT
it C \
1
I I 11- S—IT I 1 I H c — C — C — C — 11
1
C—IT-
J
1-Cyelohexyl2-propyl mercaptan
1 •
II
II
VChemical
Abstracts'
4-Mcthyl1-sulfhydrylbenzene
4-M e t h y l - 1 mercuptobenzene
Cyclopentanethiol"
SulfhydrylcycloI^entane
Mercapto— cyclopentane
1-Cyclohexyl2-propanethiol (1cyclohexane-2-propanethiol)"
1-Cyclohexyl-2sulfhydrylpropane
1-Cyclohexyh 2-rnercaptopropane
/>-Th ioeresol
preferred name.
Table II. 1. 2. 3. 4. 5.
Mercaptobenzene
II
H2C
a
l-Mercapto-2propene
k
II /
Dhenc »1 S u l f h y d r y l benzene
'
ii
V H
IT—C
H2C
1-Sulfh y d r y 1-2propene
II
Cru
A l t h o u g h common usage appears to carry a s m u c h weight as a n y o t h e r factor in d e t e r m i n i n g which n a m e is preferable, t h e I n t e r n a t i o n a l Union of Chemistry h a s i n t r o d u c e d a degree of order b y formulation of c e r t a i n nomenclature rules. These rules a r e given in t h e ''Definitive Report of t h e Commission on t h e Reform of t h e N o m e n c l a t u r e of Organic C h e m i s t r y " (4), w h i c h w a sunanimously adopted b y t h e commission and b y t h e Council of t h e I n t e r n a t i o n a l Union of Chemistry a t Liege in 1930. T h i s system of nomenclature, despite i t s strong sanction, h a s n o t come into c o m p l e t e popular usage, which indicates t h e inadequacy of t h e rules. Other s t a n d a r d references for nomenclature a r e Chemical Abstracts and Beilstein's " H a n d -
Mercaptan system
Thiol* A systematic method of naming the group of thiols, which were formerly known as mercaptans, h a s been approached much m o r e rapidly t h a n such s y s t e m s for the o t h e r sulfur groups. However, these* compounds are still referred to by m a n y different types of names. Over
Nomenclature ofTh iols
Table 1.
Compounds II
treme and that a t least one other group, the disulfides, occurs to an appreciable exlent. Types of sulfur compounds t h a t may be introduced in refining by various reactions utilizing m a t e r i a l s from outside the petroleum h a v e been excluded from this discussion. These groupings include the sulfones, sulfoxides, sulfonic acids, and allied compounds. T h e four groups thus recognized in p e t r o l e u m will he discussed individually from t h e standpoint of nomenclature.
Scoring of Various Methods of Nomenclature of Thiols
Nomenclature Requirements Present usage N a m e i n d i c a t i v e of g r o u p A p p l i c a b i l i t y t
