INDUSTRIAL AND ENGINEERING CHEMISTRY
918
Figure 9.
Vol. 41, No. 5
Stability of Diisobutylene
Owing to an intercept oi about zero on the coordinate scale (Figure 9), the relationship with tert-butylcatechol and 2,4-dimethyl-6-tert-butylphenol appears t o be linear, whereas with N,N’-di-sec-butyl-p-phenylenediamine, which possesses an s value of 0.752, the linear relationship fails. It is believed that the formulas presented will be found of value in determining an adequate yet economical dosage of antioxidant in commercial batches of gasoline.
Literature Cited
i 70
50
20
l N r i BiTOR
10
5
CONCCNTRATION,
2
PP
M
Figure 10. Stability of Diisobutylene
(1) Dryer, C. C., Lowry, C. D.. Jr., Egloff, G., and Morrell, J. C . , I X D . E N G . C H E M . , 27, 315 (1935). R. H., “Stabilization of Styrene,” payer yresent’ed (2) Egloff, G . , ~ ~ ~J . c., ~ L~ 1~ c.1 D., ~, j r , ,~and D~ ~ c, ~ c,, ~ , ~ (4)~RoSe11Wald , before Division of Organic Chemistry, 109th Meeting of ~1~ Ibid., 24, 1375 (1932). CHEM.SOC.,Atlantic City, N. J., April 1946. (3) George, P., and Robertson. A . . Proc. Roy. SOC.(London), 185, 309 (1946). R r c r r v r ~ iSeutemher 24, 1948.
Relation of tivators Roger W. Watson and Theodore B. Tom STANDARD OIL COMPANY (INDIANA), WHITING, IND.
C
ERTAIN metals, particularly copper, exert a powerful pro-oxidant effect on many organic compounds. I n the presence of oxygen and copper such compounds deteriorate in quality and in many cases form undesirable color and residues. In this way the presence of copper may lead to marked deterioration of a petroleum product, particularly cracked gasoline, notwithstanding the presence of ordinarily adequate amounts of inhibitor. The use of copper chloride sweetening has been shown t o impart small quantities of capper to gasoline stocks. The amount necessary to catalyze oxidation is considerably less than one part per million; hence careful attention must be directed to removing any metal ions thus introduced. An early approach t o the problem of removing dissolved copper salts from copper-sweetened oils involved treatment with aqueous solutions of sodium, zinc, or ferrous sulfides, or of sodium carbonate. From time to time other agents for washing out copper ions have been disclosed, among which are solutions of thiols ( 8 ) , aminothiols ( 7 ) , and sodium and potassium arsenites (20). The addition of a compound having a tendency t o combine with the metal to form a stable nonionic complex is another and singularly successful approach to the problem of combating metal catalysis. Such additives, called metal deactivators, were first described in 1939 by Downing, Clarkson, and Pedersen (9).
Their work and that of others so succesafully illuminated the harmful role of certain metals in the storage and handling of gasoline that the incorporation of metal deactivators in some fuels has become commonplace. Catalytic deterioration of motor fuels-especially those containing cracked components-is often exhibited when such fuel: are brought into contact with transportation and storage containers and fuel-system parts such as feed lines, strainers, pumps and carburetors fabricated from copper or its alloys. Oxidation and gum formation are particularly severe where the copper parts are new or where a single fill of gasoline is permitted to remain in contact with the metal for several weeks. Instances of trouble have been reported with new vehicles on display, with fueled military vehicles after a n extended period of water or rail transport, and with marine craft in which the fuel systems remained filled but inactive over the winter months. The Ordnance Department has recognized this problem and specifies (19) that fuel purchased for storage in new fuel system6 either be straight-run (virgin) or contain a n oxidation inhibilor and a metal deactivator. One of the chief uses of metal deactivators is the protection of these so-called drive-awa? gasolines. Metal catalysis is also responsible for increased rates of deterioration in lubricating oils where copper and lead appear either
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
May 1949
as soluble salts or metallic surfaces. Copper _ _ is in contact with circulating oils in bearing metals, oil lines, bronze gears, and a few miscellaneous parts, while lead is in contact with motor oils as a bearing metal and from blowby of antiknock compounds and their combustion products. Lead catalysis is commonly combated by the use of organic sulfur compounds which form protective surface films and precipitate soluble lead as inactive sulfides. Copper and lead corrosion and catalysis in lubricating oils by soluble and mass metals have been inhibited by the use of complex-forming additives. I n general, the problem in motor oils is complicated by relatively high temperatures which tend to decompose these additives. Many polyfunctional compounds have been patented as rusting inhibitors. These compounds, such as dicarboxylic acids, hydroxamic acids, and amidoximes, are known to form coordination complexes and possibly act through complex formation to protect metallic surfaces against air and moisture.
Patent Literature The earliest patent directed specifically t o metal deactivators was filed December 29, 1937, and issued November 28, 1939, to Downing and Pedersen (IO). The patent claims compositions
Table I. Carbonyl Compounds o-Hydroxy aromatic carbonyl compounds
Recognition of the action of metals, particularly copper, as oxidation catalysts for hydrocarbons has led to the relatively recent development and use of protective agents called metal deactivators. These additives are used chiefly in drive-away and copper-sweetened gasolines and in industrial lubricants, such as circulating oils. Many of the patented metal deactivators also find use in analytical chemistry as specific reagents for precipitating metals. The theory of coordinationcomplex formation can be extended to explain the relation of chemical structures to activities of metal deactivators. The effectiveness of metal deactivators depends, to a large extent, on the following structural factors: chelation, ring size, and inner-complex salt formation; electron-donating tendency of hetero atoms; tying together of chelate groups; and coplanar configuration. Metal deactivators behave similarly in the presence of soluble and metallic copper. Among the more effective copper deactivators are salicylaldehyde-1,2diamine condensation products and their derivatives and the dialkyldithio-oxamides.
Bibliography of Patent Literature on Metal Deactivators Amino Compounds
Monoamines Amino alcohols
Inventors
Schiff’s Base Type Compounds J. A. Chenicek E. R. White and E. L. Walters J. A. Chenicek I. Gubdmann F. B. Downing and C. J. Pedersen
Polyhydroxyamines Polyamines
F. B. Downing, A. M. Neal, and C. J. Pedersen C. J. Pedersen and R. 0. Bender
F. B. Downing and C. J. Pedersen J. A. Chenicek
Aminophenol
*
0-Dicarbonyl compounds 8-Keto acids, esters, amides Isonitroso ketones Benzoin
F. B. Downing and C. J. Pedersen Anthranilic acid J. A. Chenicek F. B. Downing and C. J. Pedersen a-Amino acids F. B. Downing and C. J. Pedersen Hydroxylamine Aminoguanidine R. G. Clarkson and C. J. Pedersen Semicarbazide Thiosemicarbazide E. R. White and E. L. Walters Polyamines J. A. Chenicek 1&Diamines M. H. Daskais and E. K. Fields Polyamines W. A. Schulze and G. H. Short Hydroxylamine Phosphonic and Areonic Aaids Phosphonic acids E. K. Bolton P. G. Stevens and H. S. Turner a-Hydroxy phosphonio acids M. Engelmann and J. Pikl a-Amino phosphonic acids Arsonic acids T. B. Tom S Compounda Containing the Group-&--N Thioureas C. J. Pedersen Thioamides W. E. Hanford W. A. Sohulze and G. H. Short Diphenyl thiocarbaeone Thiosemicarbazides Dithiourea R. G. Clarkeon Urea-thioureas Thiourea-guanidines R. W. Watson and C. M. Loane Dithio-oxamide
t
Thionalide (a-mercapto-N-2-naphthylacetamide) Diethyldithiooarbonate 8-Aminoethyl sulfides Hydroxyazo compounds Guanylguanidines Pyridinecarboxylic acids 5,7-Dibromohydroxyquinoline Hydroxamio acids Dihydroxamic acids Aminomethylphenol, resins and salts Anthranilic acid
919
Miecdlaneous W. A. Sohulze and G. H. Short W. A. Schulze and G. H. Short M. A. Dietrich C. J. Pedersen F. B. Downing and C. J. Wdersen C. J. Pedersen W. A. Schulze a n C G . H. Short M. A. Dietrich M. E. Cupery J. C. Zimmer and J. I. Wasson L. A. Mikeska, J. C. Zimmer, and J. I. Wasson H. G. Schutse
U. 9. Patent No.
Issue Date
2,346,662 2,300,988
April 18, 1944 Nov. 3, 1942 Oct. 24, 1944 April 18, 1944 Aug. 14, 1945 Nov. 28, 1939 h-ov. 28, 1939 May 12, 1942 May 26, 1942 June 2, 1942 June 2, 1942 Aug. 14, 1945 Aug. 14, 1945 Nov. 10, 1943 Sept. 9. 1941 July 15, 1941 M a y 12, 1942 March 23. 1943 Sept. 2, 1947 March 10. 1942 hTov. 28, 1944 Dec. 4, 1943
2,361,339 2,346,683 2,181,121 3,381,932 2,181,122 2,282,513 2,284,267 2,285,259 2,285,260 2,382,905 2,382,906 2,301,861 2 255 597 2’249’602 2‘282’936 2’314’388 2:426:766 2,276,158 2,363,777 2,336.598 2,353,690
July 18, 1944
2,285,878 2,420,122 2 388 255 2:242:622
June May Nov. May
2,230,371 2 254 124 2’304’156 kppli’cation
Feb. 4, 1941 Aug. 26, 1941 Dec..8, 1942 pending
2,373,049 2,201,170 2,242,621
April 3, 1945 May 21, 1940 B4ay 20, 1941
2,396,156
March 5, 1946
9 , 1942 6, 1947 6, 1945 20, 1941
Application pending 2,242,623 2,242,625 2 282 710 2:382:904 2,373,021 2,363,778 2,242,624 2 279 973 2’346’665 2’364’802 2’348‘638 2:302:352
hZay 20, 1941 May 20, 1941 May 12, 1942 Aug. 14, 1945 April 3, 1945
Nov. 28, 1944 M a y 20, 1941 April 14, 1942 April 18, 1944 De0 5 1944 M a y 9: 1944 Nov. 7 , 1942
INDUSTRIAL AND ENGINEERING CHEMISTRY
920
Table 11. Polyfunctional Compounds Patented in Oil Compositions U. S. Patent Issue
Compound ?rIercaptobenzothiazole P,Z'-Bipyridine Thiourea derivatives Alizarin Glyoximes Thioamides Hydroxamic acids Keto esters Thiosemioarbasones Amidoximes Salicylaldehyde polyamines
Inventor C. M. Loane hl. A. Dietrich C. M. L o m e and B. H. Shoemaker K. A. Varteressin R. 6. George and D. E. Badertoher A. Vv'. Levis M. A. Dietrich
h-0. Date 2,154,079 April 11 1939 2,198,961 April 30: 1940 2,209,464 July 30. 1940
that of the chelate compounds. In the latter, two hetero atoms of the coordinating group are so arranged that a ring, R , is formed with the metal.
/ Bu-N
S-BU \
TL
/
c-S
s--c h
-+
2,214,443 Sept. 10,1940 2,226,427 Dec. 24. 1940 2,230,691 2,279,560 2,279,973 2,321,577
Feb. 4, 1941 April 14, 1942 April14 1942 June 15,' 1943
J. 0.Clayton and B. B. Farrington E. R. White 2,322,184 June 15, 1943 J. W. Gaynor, C. N. White, a n d R. W. 2.387.323 Oct. 23. 1945 Watson
R. A. H u n t
Vol. 41, No. 5
2,420,953 M a y 20, 1947
containing di(2-hydroxyaromatic aldehyde)-aliphatic polyamine condensation products; the preferred product is N,iV'-disalicylideneethylenediamine. A search of the patent literature has revealed some fifty United States patents primarily directed to metal deactivators in cracked fuels, rubber, and chemicals. These patents are compiled in Table I, which may not be exhaustive-owing to incomplete indexing of this relatively new subject-but is nevertheless substantially complete. A breakdown of this bibliography shows that more than half of the patents listed teach some form of amine-carbonyl condensation product. The next largest group includes compounds containing the thioamide structure. Some of the many polyfunctional compounds patented as rusting inhibitors, bearing-corrosion inhibitors, and ice machineoil additives which prevent the transfer of copper from one part of the system to another are listed in Table 11. These are recognized as coordinating structures and probably function through the formation of complexes.
Effect of Structural Factors Many of the patents cited cover organic compounds that have been widely used as analytical reagents for the qualitative and quantitative detection of copper and other metals. It has been shown that these reagents combine with metals to form products in which the metal is held by coordinate as well as polar valence. These compounds are called coordination complexes. Yoe (%), Mellan (18), and others list a large number of analytical reagents capable of forming such complexes m-ith copper. The theory of complex formation and coordinate valence, as applied to these analytical reagents as well as other coordinating structures, has been developed in detail (6, 14, 16). When combined with an effective metal deactivator the stabilized valence and nonionic nature of the coordinated copper atom preclude its behaving as a n oxidation catalyst. With ineffective metal deactivators less stable copper complexes are formed. Variation in stability of other coordination complexes has been observed: some ionize sufficiently t o allow passage of electric current in solution while others do not. Factors which appear to affect the relative stability of copper complexes, and hence the effectiveness of copper deactivators, are discussed in the following paragraphs. Chelation, Ring Size, and Inner Complex Salt Formation. The simplest coordinating groups are those containing single hetero atoms (nitrogen, oxygen, sulfur, or phosphorus) and satisfying but one coordinate valence. Included in this class are water, ammonia, monoamines, and such simple ions as hydroxyl, cyanide, and chloride. Copper forms complexes with simple coordinating groups containing single hetero atoms as exemplified by copper ammine salts, A , but the stability of such complexes is much less than
R
'4
A comparison of the deactivating power of groups containing one and two hetero atoms is given in Table 111. Numbers 1, 2, and 3 demonstrate the comparative ineffectiveness of compounds containing but one hetero atom, while numbers 4,5, and 6 show the increased effectiveness obtained by connecting two hetero atoms in a single compound. Table 111. Comparison of Stability of Acyclic and Cyclic Copper Coordination Compounds Coordinating yo Restoration of KO.
Compound n-Butyl alcohol n-Butanethiol n-Butylamine 2-Meroaptoethanol Ethanolamine Ethylenediamine
Induction Period 0 0 5
5 25 70
The data presented in the tables of this paper were obtained by many workers who used the Voorhees and Eisinger (63) or A.S. T.M. D 525-46 (1) test methods on a large number of gasoline stocks of widely different induction periods, inhibitor contents, copper contents] and inhibitor responses, The authors have taken the liberty of expressing numerically the efficiency of metal deactivators in terms of per cent restoration of the induction period of the stocks to which they are added. To determine this value three induction periods for a given stock are obtained: one without copper or deact'ivator, a lower one in the presence of copper, and a third one with copper and deactivator. The difference between the second and third of these values, expressed as per cent of the difference between t'he first and second values, is the per cent restoration. This scheme can be applied only in instances where excess amounts of deactivator are used and owes its validity to the observation (9) t h a t the addition beyond a certain concentration of metal deact'ivator with no antioxidant propert.ies contributes little to the induction period of the contaminated gasoline. Although the authors have not found this to be true in all cases, the use of per cent restoration-particularly for stocks of long induction periods wherein errors of measurement are minimized-seems to approach a common basis for the data and to express the results in terms of improvement achieved. The best comparisons are obviously those made with compounds tested in the same gasoline. Throughout this work thermally cracked gasolines of high inhibitor content were used. A large body of data \vas gathered from studies with a blend containing O.Ol~obutylaminophenol and possessing an A.S.T.M. induction period of 635 minutes. The addition of 4 mg. of soluble copper (as copper oleate) per liter or of 18 inches of N o . 18 copper giro per 50 ml. lowered the induction period of the stock to 85 and 1-55 minutes, respective1.y. I n all instances 0.00570-more than the stoichiometric amount for reacting with the copper-of metal deactivator was used. When ethylenediamine was added to the gasoline containing soluble copper, the induction period rose from 85 to 465 minutes and the difference, 380 minutes, is about 70% of thf: difference between 8,5 and the original induction period of 635 minutes. The simple ahphatic amines, glycols, and mercaptans mere tested in large excess in order to obtain the desired cont,rast. All other compounds except those wit'h outside reference have been tested with a stoichiometric excess of approximately one. The formation of relatively strain-free rings, as predicted by Baeyer's theory, is conducive to greater complex stability. T h a t the five- and six-membered ring structures are more stable is shown in Table IV, where the capacities for deactivating copper of compounds from ethylenediamine to 1,6-diaminohexane are compared. The latter compound, a potential ring-forming
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1949
structure, is only slightly more active than primary monoamines. Thus it can be said that, when the two hetero atoms are separated by carbon atoms, those structures permitting formation of fiveand six-membered rings, C, are likely t o be better deactivators than t,hose forming larger rings.
(I
Influence of Ring Size on Stability of Copper Complexes No. of Atoms % Restoration of Coordinating
Table IV.
Compound Ethylenediamine I,3-Diamino ropane l,l-Diamino!&ane 1 ,&Diaminohexane
in Ring 5
Induction Period 70
7
35 15
65
6 9
Both hetero atoms in a chelate group may be neutral, as in the diamines which satisfy only coordinate valences, or the chelate groups may contain one neutral and one ionic hetero atom, in which case both coordinate and polar valences are satisfied. An example of the latter type of structure is the picolinic acid complex, D. Such compounds, called inner complex salts, are generallv stable. Several emmples are presented in Table V.
92 1
This tendency is greatest in nitrogen, decreasing through sulfur and oxygen (16). This concept is supported by data for simple chelate compounds (examples 4,5, and 6 in Table I and 1, 2, and 3 in Table VI) and by data for inner complex-salt-forming structures (examples 4,5, and 6 in Table VI). Tying Chelate Groups Together. A comparison of the deactivating capacity of monoamines with diamines (examples l and 2, Table VII) and of these with similar salicylaldehyde derivatives (examples 3 and 4) shows a progressive increase roughly corresponding t o the increase in the number of functional groups in the molecules. This increase arises from connecting the individual hetero atoms. Thus, one molecule of the quadridentate compound, N,N’-disalicylidenetthylenediamine, fills all four coordinate positions of copper and the resulting complex, E, is more stable than t h a t formed from copper and two didentate molecules of N-salicylideneethylamine, F. N,N‘-disalicylidenehydrazine (example 5), however, has a low order of effectiveness, as the two chelate groups cannot completely coordinate one copper atom because of the proximity of the nitrogen atoms and their inability to form a satisfactory third ring with the metal. Calvin and Bailes ( 2 ) have concluded that, among the factors influencing chelate stability, (‘, . . , , .the effect of tying together coordinating groups is by far the largest and most important.” Ilor (1‘7‘) has explained this phenomenon by pointing out t h a t a system of appropriately connected coordinating groups possesses increased entropy arising from the improbability of decomposition through the simultaneous dissociation of the coordinating groups.
D Table V.
Stability of Inner Complex Salts % ’ Restoration of
Compound a-Benzoin oxime 8;Hydr.oxyquinoline Pieollnic acid Alizarin
Induction Period
30 80 75 65
Electron Donation. Through donation of unshared electrons by hetero atoms, the electronic configuration of copper approaches that of krypton and attains the stability associated with the inert gas elements. The stability of the coordinate linkage increases as the elrctron-donating tendency of the Iietero atom increases.
P Examples 6 through 9 show a progressive decrease in effectiveness among the 2-hydroxyacetophenone derivatives of ethylenediamine, 11,3-diaminopropane, 1,6-diaminohexane, and 1,10-
Table VII.
Effect of Tying Together Chelate Groups Restoration % Compound
n-Butylamine Ethylenediamine
1 2
N-Salicylidene8thylamine N,N’-Disalicylideneethylenediamine N,N’-Disalicylidenehydrazine ethulenenT.N’-Bis (ol,5-dimeth~lsalic~lidene) diamine (from 2-hydroxy-5-methylacetophenone) 7 N,N’-Bis(u,5-dimethylsalicylidene)1,3-propctnediamine €4 N,N’-Bis(ar,5-dimethylsalicylidene)1,6-hexanediamine 9 N,N’-Bis ol,5-dimethylsalicylidene) 1 ,lodecanehiamine 10 N,N’-Bis(ar,5-dimethylsalicylidene)triethylenetetramine 3
Table NO. 1
2 3
4 5 0
VI.
Influence of Electron-Donating Tendency of Hetero Atoms on Stability % Restoration of Compound
Glycol 2-Mercaptoethanol Ethanolamine 2-Hydroxybcnzoic acid (salicylic acid) 2-.\Iercautobenzoic acid (thiosa!icylic acid) 2-.lminobenzoic acid (anthranilic acid)
Induction Period 0 6 25
5 15 4.5
4 5 6
11
I
Salicylaldoxime
of Induction Period 5 70
Reference
5 100 15 100
(11)
17
(11)
3
(11)
3
(11)
50
(12)
95
922
INDUSTRIAL AND ENGINEERING CHEMISTRY
diaminodecane, reaching in the last two examples a level similar to what might be expected were the two imino gioups uncoiinected. The ineffectiveness of the l,6-diaminohexane and 1,lOdiaminodecane derivatives of 2-hydroxy-5-methylacetophenonr is explained by the decreased proximity of ihr t w o halves of the molecule after dissociation. The tn.0 extra hetero atoms in the complex of the triethylenetetramine derivative (examplr 10) appear partially to overcome thi- effect. In certain structures hydrogen bonding may takr the place of a carbon chain in tying together the two halves of the complex. This would account for the marked effectiveness (euample 11) of salicylaldoxime, G. as against the rrla tivr inrff ertivrnrs(example 3) of the simple imine, F.
Vol. 41, No. 8
methyl and then an ethyl group. Molecular models indicsatr an increasing interference in the coplanar copper complexer. A rimilar steric effect is predicted by Duffield and Calvin ( 1 3 ) for the 1,8-diaminonaphthalene derivative of 2-hgdro.;yarrtophrnone. Pfeiffer (21, 28) noted that the inolecuIar weight of the .V,.V’disalicylidene-mphenylenediamine copper complex is double that of the expected compound and that the complex has very low solubility. He concluded that this and some similar coniplexes are bimolecular in that two atoms of copper are held hetween two molrciilcs of t h r coordinating structure as shown in H .
H
....q
0-H I
G Coplanar Configuration. The steric ability of the hetero atoms to form a coplanar configuration on coordination with copper is R determining factor in the stability of metal deactivators. Distortion of t,hc coordination plane reduces the stability of the complex (3). Table VI11 shows the effect of substituents on Ihe carbon atoms of ethylenediamine, both as the free amine (examples 1 and 2) and as the 2-hydroxy-5-met~hylacetoplienonediamine derivative (examples 3, 4, and 5 ) . The decrease i ~ ; metal-dea.ctivator effectiveness with incrrased suhstit,ution may well be a reflection of steric int,erference.
Table VIII.
Effect of Carbon Substituents on Ethylenediamine and Its Condensation Products 56 Restoration
Compound No. I Ethylenediamine 2 1,2-Diaminopropane 3 4 5
S,S’-Bij(e,5-dimethylsalicylideiie)ethylenediamine S,S’-Bis (a,5-dimethylsalicylidene) 1,Z-pro. panediamine S ,A-’-Bis (a,5-dimet hylsalicylidene) 3,4hexanediamine
of Induction
Period
Refweircc
100
fir;
86
(11:
78
(1.1:
I n Table I X examples I, 2, and 3 show data from a series ramprising the oximes of salicylaldehyde, 2-hydroxyacetophenone, and 2-hydroxypropiophenone. A regular decrease in effectiveness may be noted as the aldehyde hydrogen is replaced hi. R
Table IX.
Steric Interference with the Coplanar Structure c/o Restoration
of Induction S O .
Compound
1 Saliaylaldoxinie 2 Z-Hydroacetophenone oxime 3 2-Hydroxypropiophenone oxime 4 ,~r,.~-’-Bis(3-hydroxybenlyl~dene) 1.2-propanediamine 5 X,N’-Bis (4-hydroxybcnzylidene) 1,2-propanediamine ij Dimnthyldithio-oxamide
Period 95 85 65
75
--i J
100
Referelice (12) (12) (?#!
H
‘The effectiveness of t,he diamine derivatives of 3- and 4hydroxybenzaldehyde (examples 1 and 5 in Table IX) introduces anot’her question of structure. Although the complexes of these compounds will not fit into a pattern like that proposed by Pfeiffer, plausible structures are obtained by superimposing two F-shaped molecules in head-to-t,ail arrangement about, two atoms of copper. h similar condition appears t o obt,ain with the very effective dimethyldithio-oxamide. A coplanar structure: coordinating one copper atom with one molecule of dimethyldithio-oxamide is impossible, but a satisfactory arrangement can be effected by superimposing two molecules of deactivator, headt,o-iail rather than sidc by side as in H , so that two atoms of copper are coordinated between them. Polymeric struct,ures slso permit coplanar configurat,ion in molecules of this type. Resonance. Factors dependent upon the resonarice charac:trristics of copper-complex structures of acetylacctone, 2-hydroxy1-naphthaldehyde, and salicylaldehyde are shown by Calvin and Wilson (3)to cause a decrease in stability in this relative order, These compounds do not function as metal deactivators in gasoline; hence, differences here are not, observable (examples 1, 2, and 3. Table X), However, three comparisons of the deactivator effectiveness of salicylaldehyde and 2-hydroxy-l-riapht,haIdehyde derivatives are available---namely, the oximes (examples 4 and 5), butylamine derivatives (examples 6 and 7), and et’hanolaminr derivatives (examples 8 and 9). No significant differences appear. Ethylacetoacet,ate (example lo) and its ethylenediamine derivative (example 11) are, respectively, less effective than acetylacetone (example 1) and ite corresponding derivative (example 12), owing to the interference of the ester structure with the enolate resonance of the complex (3). While it has been shown (IS) that, because of a greater resonance energy, the copper complex of the acetylacetone-ethylenediamine compound is more stable than that of the salicylaldehyde-ethylenediamine compound (example 13), a reverse effect appears in copper-deactivator effectiveness. These conflicting data indicate that metaldeactivator effectiveness tends t o be less dependent on the resonance fa,at,ors involved, or that, ot,hor factors offset these effects.
May 1949
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
923
Acknowledgment Comparison of Structures of Varying Reasonance Energies % Restoration Inducof Induction tion ReferN 0. Compound Period Period ence 5 1 Acetylacetone 2 2-Hydroxy-1-naphthafdehyde 0 3 Salicylaldehyde 0 4 Salicylaldoxime 95 (la 6 2-Hydroxy-1-naphthaldoxime 90 (18) 6 N-Salicylidenebutylamine .. 2205 (4) 7 N-(2-Hydroxy-l-naphthylmethylene) butylamine (from 2-hydroxy-l2256 naphthaldehyde) ..
Table X.
.
8 N-Salicylideneethanolamine
9 N-(2-Hydrox,y-l-naphthylmethylene)
ethanolamine 10 Ethyl acetoacetate 11 N,N’-Bis (carbethoxyiaopropylidene) ethylenediamine(from ethyl acetoacetate) 12 N,N’-Bis (1-methyl-3-oxobutylidene) ethylenediamine (from acetylacetone)
I
..
200a
if1
..
220“
(6)
0
..
10
..
45
..
13 iV,N’-Disalicylidene(ithy1enediamine 100 a Data necessary for calculation of induction-period restoration were not given, hence induction periods themselves are shown for comparison.
Comparison of Forms of Copper The catalytic effects of dissolved and metallic copper in gasoline deterioration are much the same. The probable explanation is that advanced by Walters ($4): The mass metal must go into solution before it is able t o affect the oxidation stability of the oil. Nevertheless some coordinating structures (examples 1 and 2, Table XI) show different degrees of effectiveness against the two forms of copper. Table X I also lists a deactivator that behaves similarly in the presence of both forms of copper.
Table XI.
No. 1 2
3
Effect of Metal Deactivators on Metallic and Dissolved Copper % Restoration of Induction Period Soluble MetZ1K-l. Compound Copper Copper N,N’-Disalicylidene-l,2-propanediamine 90 55 Quinolinic acid 110 40 Dimethyldithio-oxamide 100 100
The authors wish t o express their appreciation to C. E. Adams of this laboratory for furnishing some of the data presented in Tables VI1 and IX.
Literature Cited (1) Am. So?. Testing Materials, “Standards on Petroleum Products and Lubricants,” p. 339 (1946). ( 2 ) Calvin, M., and Bailes, R. H., J.Am. Chem. SOC., 68, 949 (1946). (3) Calvin, M., and Wilson, K. W., Ibid., 67,2003 (1945). (4) Chenicek, J. A., U. S. Patent 2,346,662 (April 18, 1944). (5) Ibid., 2,346,663 (April 18, 1944). (6) Diehl, H., Chem. Revs., 21, 39 (1937). (7) Dietrich, M. A,, and Pedersen, C. J., U. S. Pateirt 2,411,958 (Dec. 3, 1946). (8) Ibid., 2,411,959 (Dec. 3, 1946). (9) Downing, F. B., Clarkson, R. G., and Pedersen, C. J., Oil Gas J., 38(II), 97 (1939). (10) Downing, F. B., and Pedersen, C. J. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,181,121 (Nov. 28, 1939). (11) Ibid., 2,255,597 (Sept. 9, 1941). (12) Ibid.,2,336,598 (Dec.4, 1943). (13) Duffield, R. B., and Calvin, M., J . Am. Chem. Soc., 68, 557 (1946). Cl?) Emeleus, H. J., and Anderson, J. S., “Modern Aspects of Inorganic Chemistry,” New York, D. Van Nostrand Co., 1938. (15) Feigl, F., “Specific and Special Reactions for Use in Quantitative Analysis,” t r . by R. E. Oesper, New York, Elsevier Publishing Co., 1940. (16) Gilman, H., “Organic Chemistry,” p. 1896, New York, John Wiles & Sons, 1944. (17) Iler, R. K., J . Am. Chem. S O C . , 69,724 (1947). (18) Mellan, I., “Organic Reagents in Inorganic Analysis,” Philadelphia, Blakiston Co., 1941. (19) Ordnance Dept., S u p p l y Bull. 9-4 (Aug. 20, 1944). (20) Paulsen, H. C., E’. S. Patent 2,324,948 (July 20, 1943). (21) Pfeiffer, P., Breithe, E., Luebbe, E., and Tsumalu, T., Ann., 503, 84 (1933). (22) Pfeiffer,P., and Pfitzner, H., J.pralct. Chem., 145(11), 243 (1936). (23) Voorhees, V., and Eisinger, J. O., S.A.E. Journal, 24, 584 (1939). (24) Walters, E. L., Minor, H. B., and Yabroff, D. L., IND.ENG. CHUM.(in press). (25) Yoe, J. H., and Sarver, L. d.,“Organic Analytical Reagents,” New York, John Wiley & Sons, 1941. R E O F I Y F I D September 24, 1948.
Other Considerations Compounds t h a t meet the structural requirements necessary for successful metal deactivators are rather generally available. Some, however, fulfill these structural requirements but are not suitable for use in petroleum products because of other properties. , I n some instances lack of hydrocarbon solubility precludes Amino acids are their consideration as deactivators. especially insoluble. Some of the other compounds discussed are not directly soluble in gasoline but may be used in alcoholic solution. Alkylation, of course, presents another method of solubilizing. Thus the N , N ’ dimethyl derivative of dithio-oxamide is much more soluble than the unsubstituted compound. Certain compounds such as diphenylcarbaaide and diphenyl-thiocarbaaone form brightly colored complexes with copper in gasoline but fail to keep the copper ions properly masked under the relatively severe conditions of accelerated tests. It may be t h a t many additives are able successfully to deactivate copper in long-term storage tests at lower temperatures, but this point, has not been extensively investigated.
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COURTESY STANDARD O I L OF OALIFORNIA
T i m i n g Test Engine a t Coordinating Research Council Laboratoriee
