US3557169A - Process for producing carboxylic acids - Google Patents

Abstract

A PROCESS FOR PRODUCING STRAIGHT CHAIN UNSUBSTITUTED MONABASIC CARBOXYLIC ACIDS HAVING FROM ABOUT 7 TO ABOUT 19 CARBON ATOMS PER MOLECULE WITH IMPROVED SELECTIVITY BY OXIDATION OF SELECTED OLEFINS. ALPHA OLEFINS ARE DIMERIZED TO PRODUCE ETHYLENES CONTAINING AT LEAST 1,1DISUBSTITUTION WITH A METHYLENE GROUP IN THE ALPHA POSITION OF AT LEAST ONE OF THE SUBSTITUTING RADICALS. THE ETHYLENES ARE OXIDIZED SELECTIVELY TO PRODUCE CLEAVAGE OF THE MOLECULE AT THE LINKAGE OF THE METHYLENE GROUP OF THE RADICAL TO THE BALANCE OF THE SUBSTITUTED ETHYLENE MOLECULE.

Description

PROCESS FOR PRODUCING CARBOXYLIC ACIDS Gene C. Robinson, Baton Rouge, La., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Continuation-impart of application Ser. No.

460,558, June 1, 1965. This application Oct. 29, 1968,

Ser. No. 771,670

Int. Cl. C08h 17/36 US. Cl. 260-413 3 Claims ABSTRACT OF THE DISCLOSURE A process for producing straight chain unsubstituted monobasic carboxylic acids having from about 7 to about 19 carbon atoms per molecule with improved selectivity by oxidation of selected olefins. Alpha olefins are dimerized to produce ethylenes containing at least 1,1- disubstitution with a methylene group in the alpha position of at least one of the substituting radicals. The ethylenes are oxidized selectively to produce cleavage of the molecule at the linkage of the methylene group of the radical to the balance of the substituted ethylene molecule.

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 460,558, filed June 1, 1965, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the production of straight chain unsubstituted monobasic carboxylic acids having from about 7 to about 19 carbon atoms per molecule. In greater particularity, the invention relates to the selective production of acids having a narrow range of molecular weight of compounds in a given product mixture so as to facilitate purifications and separations of product acids and to provide enhanced economics in producing specific desired product acids and narrow molecular weight range mixtures having fairly closely related similar properties. The process employs oxidation of sensitized olefins having sensitivity to oxidative attack and cleavage at only a few particular definite points in the molecule brought about 'by a molecular configuration characterized by the presence of a side chain having more than one carbon atom attached to a carbon atom which forms a part of the olefinic double bond linkage of the molecule. Typical olefins that are useful in such an oxidation are those characterized as vinylidene olefins and tri-substituted ethylenes, particularly those tri-substituted ethylenes having methyl as one of the substituting groups of the 1,1- positional substitutions.

Description of the prior art The oxidation of hydrocarbons to produce various oxygenated materials, particularly carboxylic acids, has been explored for many years. Prior efforts in this line have encountered the very serious fundamental difficulties that the selectivity of conventional partial oxidation operations with hydrocarbons, even olefins, is very poor. In particular, with saturated hydrocarbons the point of oxygen attack upon the carbon atoms of the molecule is not limited to any specific carbon atom. Since the conversion of an alkane molecule to carboxylic acid after an initial attack on an internal carbon atom generally involves cleavage in the hydrocarbon molecule involved, the result is that, for the most part, each hydrocarbon molecule oxidized to acid produces two or more short chain acids and these can vary in number from formic acid all the way to the maximum number of carbon atoms per molecule in the feed employed or obtained.

United States Patent Thus, if one were to seek, for example, the production of a particular acid or of a narrow range of acids, say dodecanoic, tridecanoic, and tetradecanoic, having generally similar properties in certain desired uses, such as detergent or cleaning soap materials, one finds that the yield of the desired acids is quite small in terms of weight of desired acids produced per unit weight of feed hydrocarbon. The foregoing lack of selectivity of oxidation is generally similar with unsaturated molecules even olefins of straight chain carbon skeleton configuration. In general, there may be a minor sensitization of certain carbon atoms in some ordinary olefinic molecules; however, as a practical matter such a sensitization is normally so small as to be virtually insignificant in ordinary types of operations under commercial large scale conditions.

Another disadvantage of prior hydrocarbon oxidation connection with the lack of selectivity of oxidation of molecules such as of alkane hydrocarbons, is the production of difunctional molecules such as keto acids, hydroxy acids, and dibasic acids due to the occurrence of attacks on several carbon atoms of individual hydrocarbon molecules. Although such difunctional molecules may be desired in some instances, they are not normally desired when the production of monocarboxylic acids of high purity is sought because esterification occurs between the carboxylic acid groups and the hydroxy groups and various condensations involving carbonyl groups are likely to occur. The results of such molecular combinations is the loss or difiicult recovery of materials of the desired product range due to the formation of heavy molecules of esters and the like which are difiicult to resolve into desired product range components.

It is of course well known that various kinds of hydro carbons, unsaturated as well as saturated, have been subjeoted to oxidation such as outlined in the foregoing. Olefins seemingly present certain advantages in obtaining some selectivity due to the double bond; however, with the type of ordinary olefins used in prior art oxidations it is almost as difiicult to obtain low cost olefins which are pure as regards location of the double bond as it is to obtain selectivity of oxidation of alkane molecules. Alpha olefins can be relatively pure but they are costly. Although numerous direct dehydrogenation processes are known, and there are others which involve various manipulation sequences such as halogenation of alkanes followed by dehydrohalogenation, or oxidation of alkanes to secondary alcohols followed by dehydration, there is always the question of selectivity. As a practical matter, one should be prepared to expect a random distribution as to the location of olefinic double bonds resulting from such processes and therefore as to the molecular weight of product carboxylic acids resulting from the oxidation of such.

Although the direct dehydrogenation of alkanes was introduced in the foregoing paragraph as a source of olefins, normally this process is not very attractive particularly when dealing with hydrocarbons having from about 10 to 20 carbon atoms per molecule because in addition to a lack of selectivity of the point of dehydrogenation, unless the olefins produced are removed from the dehydrogenation mass as soon as they are formed. which is difficult, there is a high probability that additional dehydrogenation of the monoolefins will occur producing molecules with various forms of multiple unsaturation such as acetylenes and diencs. It will be readily recognized that the oxidation of dienes will produce cleavage at two points in the molecule resulting in the production of a higher percentage of acids of short chain length.

SUMMARY The process of the present invention provides highly selective production of monobasic carboxylic acids of straight chain carbon skeletal configuration ranging from about 7 to about 19 carbon atoms per molecule. Although this broad range is set forth, it is characteristic of the selectivity capabilities of the process of the present invention that by appropriate choice of starting olefin, homologous series product acid mixtures are produced which involve predominantly a selected spread of only about 4 or 5 carbon atoms per molecule. As a practical matter when starting with a typical pure olefin such as decene-l, then dimerizing and oxidizing according to the present process, acids predominating in those having from 7 to 11 carbon atoms per molecule are obtained. In another illustration with another pure typical olefin starting material, octadecene-l, dimerization and oxidation in accordance with the teachings of the present invention provides straight chain monobasic carboxylic acids predominating in those having from 15 to 19 carbon atoms per molecule. For intermediate molecular weight olefins, substantially the same relationships between molecular weight of starting olefins and of product acids are realized.

Where the starting olefin is a mixture of olefins as typified for example by a mixture of decene-l and octadecene-l, the dimerization products include combinations of the different molecular weight olefins. In general, the oxidation of such results in two spectra of acids being produced, one corresponding to the products of each olefin as a pure olefin. Thus to follow through with the illustration, where a typical mixture of decene-l and octadecene-l is employed for dimerization and the dimerization product is oxidized, the acid products predominate in one spectra having from 7 to 11 carbon atoms per molecule and another spectra having from 15 to 19 carbon atoms per molecule.

To expand the illustration using 3 or more olefins of different molecular weight in the starting olefins employed for dimerization, additional spectra of acids are obtained. Thus where one feeds three typical olefins, decene-l, tetradecene-l and octadecene-l, one obtains acids ranging from 7 through 19 carbon atoms per molecule.

The information of the preceding paragraphs is summarized in the following equation representations.

18 carbon atoms per molecule. C=carbon atom, hydrogens being omitted.

Isomerization of vinylidene dimer RCOC=C ROC=OC RCCC-C R'C o R"C o RC o REARRANGING FORMULAS AND ADDING SIGNIFICANT H ATOMS A generic representation of the foregoing proximately branched olefin is:

wherein:

R =methyl radical or straight chain alkyl radical having from about 7 to about 18 carbon atoms per radical.

R =straight chain alkyl radical having from about 7 to about 18 carbon atoms per radical.

R =H, methyl radical or straight chain alkyl radical having from about 7 to about 18 carbon atoms per radical.

With the proviso that when R is straight chain, R is methyl.

The foregoing olefins preferentially tend to produce mainly R R and R acids plus R 0, R C, R C and R CC acids. In many instances the one and two carbon atom fragments evolve as non-acid molecules and in any event are not in the desired product range. Thus limited, highly selective, product acid spectra are obtained.

Where dimerization is employed, an R of 18 corresponds to a C starting olefin.

[Carbon Atoms in Principal Product Range Acids] Starting olefin to dimerization Tetra- Octa- Decene-l deeene-l decene-l Acid skeleton:

RG C7 C11 C15 C12 C16 C13 11 C13 C1 C14 C18 C15 10 RCCCOOH, RCCCCOOH, and RCCCCCOOH Particularly preferred product acids and oxidizing olefins are those wherein the product acids are predominantly in the C to C range and R and R are straight chain alkyl radicals having from about 10 to about 14 carbon atoms per radical and R is hydrogen. The foregoing preferred olefin is preferably pure or in admixture with olefins wherein R is methyl radical and R and R are straight chain alkyl radicals having from about 10 to about 14 carbon atoms per radical.

Another preferred oxidizing olefin is one wherein R and R are straight chain alkyls having more than 10 but not more than 14 carbons and R is hydrogen or a straight chain alkyl having up to 18 carbons.

The oxidizing of the foregoing olefins to produce acids is carried out at a temperature from 75 C. to about C.

OBJECTS It is accordingly an object of the present invention to provide a process wherein a low cost readily producible oxidation feed stock is employed which imparts selectivity to the oxidation process and which readily oxidizes at selected points at comparatively low temperatures at which oxidations at non-selected points cannot occur.

Another object of the present invention is to provide a process whereby olefins possessing a high uniformity of structure can be obtained readily and which oxidize with a high degree of selectivity.

Another object of the present invention is to provide a process whereby certain branched chain olefins, the product of a particularly advantageous processing sequence, can be oxidized with high selectivity to produce straight chain monocarboxylic acids.

Other and further objects and features of the present invention will become apparent upon a careful consideration of the following description of certain preferred embodiments of the present invention.

DISCUSSION In accordance with the teachings of the present invention, a process is provided whereby olefins obtainable for example by direct dehydrogenation or other suitable processes such as chain growth, polymerization, halogenation-dehydrohalogenation and the like are convertible to dimerized olefins which are oxidized readily to produce in high yield straight chain monobasic carboxylic acids of selected molecular weight. The dimerized olefin configurations apparently are much more readily oxidized near the center of the molecule than other materials because of the fact that these molecules contain a double bond plus branching in proximity to the double bond plus at least one methylene carbon atom adjacent to the branching. These olefins contain at least the 1,1-disubstituted configuration, at least one of the l substitution radicals containing a methylene carbon atom in the alpha position. The following illustrates the nature of these olefin configurations.

C=CH2 and R-C=CHR ROHZ (1) (2) (vinylidene (flirt-substituted Olefin) Olefin) (1,1-disubstituted ethylenes) where the R groups are straight chain alkyl and may be different. The desirability for the methylene carbon atom effectively eliminates molecules where the R groups are all methyl. The amount of isomers of the tri-substituted dimer having the double bond at positions other than the above should be kept small in those instances where minimum formation of branched acids is desired as is explained further at a subsequent point of the specification. It has been discovered that such dimerized olefins will oxidize with great selectivity at the sensitized alpha carbon of the alkyl radicals, the methylene carbon adjacent to the branching, to produce almost exclusively chiefly four sizes of oxygenated materials, a first pair which has a quantity of carbon atoms per molecule which is equal to the number of carbon atoms in the alkyl groups on the far side of the carbon atoms linked by the double bonds, the second pair which includes the adjacent linked carbon atom with one of the alkyl groups of the dimerized olefins. Once such a molecule begins, the selective oxidation, then the cleavage as described follows the unique pattern, The fifth size of oxygenated materials, frequently disregarded, arises from the 1,1,2-tri-substituted ethylenes.

In greater particularity, a typical vinylidene dimer, also called a 1,1-disubstituted ethylene, whose parent vinyl olefin components have the same number of carbon atoms (RCC=C) has the configuration i RCCOCCR where both R groups have the same number of carbon atoms. This oxidizes to produce chiefly RCOOH,

RCCOOH, RCCCOOH and RCCCCOOH acids within the relationships of this paragraph.

The availability of suitable vinylidene and tri-substituted olefins in sufiicient purity for this oxidation is an immediate problem because until now, olefins of such structure have largely been regarded as undesired byproducts of certain polymerizations or of chain growth according to Ziegler technology where one seeks to produce vinyl olefins and they are not readily obtainable directly from petroleum or other natural sources of hydrocarbon types of materials. It has been discovered, however, that random olefins are readily isomerized to alpha olefins (even if only momentary) in a catalytic environment such as with triisobutyl aluminum at temperatures from about 250 C., more preferably 100- 200 C., typically C., and that without specifically requiring the normally very difficult separation of alpha olefins from the reaction mass, the alpha olefins only will dimerize in the same environment to produce vinylidene olefins of the long chain length desired. One normally views this reaction itself as being undesirable because it involves an isomerization environment and even the vinylidenes isomerize to the tri-substituted form which one would not expect to be desirable oxidation feed to produce straight chain acids. In this instance it has been discovered that surprisingly the tri-substituted olefins are virtually as suitable as oxidizer feed as are vinylidene olefins, and that mixture of such dimers are quite suitable for selective oxidation.

The starting olefins used for dimerization can be pure as regards number of carbon atoms per molecule or they can be mixed, depending upon various factors such as source, cost and the like. With mixed olefins the dimer olefins are less symmetrical in terms of length of the R groups than with pure starting olefins. If the source of the internal olefins is dehydrogenation of saturated hydrocarbons, an important advantage of the combination of such into an overall process is that it is not necessary to remove the unreacted saturated hydrocarbons from the dehydrogenation effluent prior to the combined isomerization-dimerization treatment. The only separation needed is a post-dimerization separation which is relatively easy because the dimers have virtually double the molecular Weight of the unreacted paralfins and nondimerized olefins and are therefore readily separated by distillation so that the non-dimerized materials can be reprocessed.

Numerous advantages of the foregoing dehydrogena tion-isomerization-dimerization-oxidation process are immediately apparent because this process provides a method of readily obtaining high molecular weight olefins which oxidize selectively and difficult separations of isomers are not required.

In addition to this advantage, the selective oxidation of dimer olefins occurs under much milder conditions than the usual non-selective oxidation of saturated hydrocarbons so that conditions can be used in which nondirected oxygen attacks are virtually avoided. This brings about a remarkable reduction in the amount of difunctional molecules produced which has numerous beneficial results in subsequent purification steps. Specifically, esterifications and various condensations are largely avoided and the only unsaponifiables present in the oxidate are mainly unoxidized olefin dimers, allylic alcohols and hydroperoxides all of which have virtually as many carbon atoms per molecule as the desired longer chain product acids, simplifying unsaponifiable separation considerably.

In the isomerization of random olefins, alpha olefins are normally produced readily; however, they do not remain but isomerize back to internals. The equilibrium mixture is undesirably low in alpha olefins. The dimerization technique provides a way of grabbing the alpha olefins before they revert to the internal form because only these alpha olefins will dimerize. The dimer is ini- 7 tially a vinylidene type olefin (l,1-disubstituted ethylenes):

however, this olefin is itself subject to isomerization with the double bond moving to a position adjacent to the R or RC group. This produces the tri-substituted ethylenes The equilibrium mixture is about percent vinylidene and 80 percent tri-substituted.

Thus a dimer feed for oxidation will range between all vinylidene, where one removes the dimers virtually as fast as they are formed so as to reduce the formation of tri-substituted olefins, up to the 20 percent vinylidene equilibrium mixture. All of the possible ratios oxidize to about the same result with the tri-substituted form producing a slightly wider range of acids, but all are straight chain.

The foregoing is subject to a limitation in that the trisubstituted dimers of the foregoing, such as C-CII3 R'C also will isomerize to tri-substituted olefins with the double bond no longer adjacent the tertiary carbon atom, such as (with a single H shown for clarity). This olefin will oxidize but not as readily as the preferred types under the specified conditions; however, it will produce a significant quantity of branched acids and where this is undesired, the dimer isomerization is not permitted to continue for such extended periods that would permit any significant quantity of this latter type of olefin to be formed.

As oxidation catalysts, one may use various conventional systems such as tertiary butyl hydroperoxide, man ganous stearate, of about 0.1 to about 1.0 percent, mixtures of 0.1 weight percent of cobalt or cobalt-containing material and an equal molar amount (cobalt to bromine) of bromine or bromine-containing material such as cobalt acetate and ammonium bromide, cobalt bromide, cobalt naphthenates, etc. In addition copper and vanadium salts, organic as well as inorganic, may be used.

One will note that the oxidation is performed at low temperatures, such as from about 75 to about 110 C. at which temperatures non-directed attacks on random carbon atoms are virtually avoided. A typical preferred temperature is about 105 C.

In certain instances the oxidation is advantageously performed in inert diluent media, typical reasonably inert diluents being acetic acid and propionic acid.

In addition to the foregoing discussion of catalytic oxidation, chemical oxidation using strong oxidants such as nitric acid with vanadium catalyst, oxides of nitrogen, and the like are beneficial in some instances, in all cases however conditions are controlled so as to provide reasonable rates for directed or selective oxidation and insignificant rates for the more difficult non-selective or random oxidations.

Typical olefins oxidized in accordance with the present invention, alkyl radicals listed being normal.

R1 R2 R Typical name 001731 Ootyl H 2-octyl decene-l.

o Nonyl H 2-octyl undecene-l. Do Decyl H 2octyl dodecene-l. Undecyl H 2-octyl tridecene-l. Dodecyl. H 2-octyl tetradecene l. Tridecyl H 2-octyl pentadecene-l. Tetradecyl. H 2-octyl hexadecene-l. Do Pentadecyl H Z-ootyl heptadecened. Do Hexadecyl H 2-octyl octadecene-l. Do Heptadecyl H 2-octy1 nonadecene-l. Do Octadecyl H 2-octyleicoseSne-1.

R1 R2 R3 Typical name Methyl"-.. Octyl Heptyl Q-methyl heptadecene-S.

D0 Octadecyl Octadccyl ZO-rnethyl octatn'acontene-IQ.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Thirty parts of Z-n-butyl-l-hexene of 99 percent purity was oxidized with oxygen at 106 C. for approximately 4 hours. Tertiary butyl hydroperoxide (1 percent) was added at the start. Approximately 20 percent of the olefin reacted. To this mixture was added 1 percent manganous stearate and oxidation continued for approximately 5 hours at approximately 106 C. when the total olefin oxidized was approximately 75 percent of the starting amount.

The product had an acid number of 5 6.

The acids were extracted with a 7 percent sodium carbonate solution. The sodium carbonate extract was extracted twice with ether and acidified with HCl. The acids were extracted with ether and the extract distilled to remove the ether.

The resulting crude acids which were of a light straw color were analyzed by vapor phase chromatography yielding major amounts of n-propionic acid (52 weight percent), normal butyric acid (12.6 percent), normal pentanoic acid (9.3 percent) and normal hexanoic acid (11.4 percent) with no other major peaks.

The crude acids were 10 percent by weight of the starting material and corresponded to an average molecular weight of 100.

In this experiment, identification of major products was of main concern and the overall yield was not of great significance.

Example 2 To a stirred reaction flask was added 31.0 grams of tetradecene dimer percent vinylidene plus tri-substituted), 25 grams of glacial acetic acid and 0.3 grams manganous stearate. This mixture was oxidized for 14 /2 hours at about 106 C. Oxygen uptake was slow for the first half hour, rapid during the next two hours, and

tapering olf to virtually zero during the balance of the period.

36.3 grams of reaction product (exclusive of acetic acid) was recovered. This product was 33.7 percent fatty acid (weight), with 75 percent of those acids falling in the (311-015 range.

Example 3 To a stirred reaction flask was added 48.5 grams of tetradecene dimer of Example 2 and 0.5 gram of manganous stearate. This mixture was oxidized for 12 /2 hours at 106 C. The crude oxidate weighed 52.0 grams, and was 17 percent crude acids. Of the crude acids 43 weight percent was fatty acids (straight chain saturated monofunctional carboxylic acids) with 36 percent of the crude or 84 percent of the fatty acids falling in the range of 11 to 15 carbon atoms per molecule. Distribution by carbon atoms per molecule was as follows:

Example 4 To a stirred reaction flask was added 40.6 grams of decene dimer. This material contained 30 percent vinylidene olefin and 70 percent of tri-substituted olefin Acid (carbon atoms per molecule):

Weight percent 1.3 3.1 8.2

Example 5 Example 4 is repeated using mixed decenes as feed for concurrent isomerization-dimerization with similar results.

Example 6 A mixture of decane and decenes resulting from dehydrogenation of decane is subjected to concurrent isomerization and dimerization at 188-200 C. under autogenous pressure for 20 hours using 1 percent diisobutyl aluminum hydride. The dimers are recovered by distillation and the non-dimers are retained for further isomerization-dimerization. Thedimer product is approximately 30 percent vinylidene C and 70 percent C tri-substituted olefin of formula Example 5 is repeated with mixed decenes obtained from chlorination and dehydrochlorination of decane. Similar results are obtained.

Example 8 Examples 5 and 6 are repeated with other typical olefin mixtures such as mixed tetradecenes and mixed hexadecenes and with mixed molecular weight materials such as mixtures of decenes, undecenes, dodecenes, tridecenes, tetradecenes and pentadecenes, hexadecenes, heptadecenes, and octadecenes. Similar results are obtained with the various molecular weight materials producing various configurations of vinylidene olefins and tri-substituted olefins.

Example 9 Example 1 is repeated using 1.0 mol of the olefin which is added to 5.0 moles of 70 percent (wt.) nitric acid containing 0.2 g. ammonium metavanadate. The temperature is maintained at -60 during addition and for an additional two hours. After standing overnight at 25, the acid product is collected by ether extraction and purified by extraction with caustic and reacidification. Similar results are obtained.

Example 10 Example 1 is repeated. A mixture of ml. of percent nitric acid and 0.1 g. ammonium metavanadate is put in a three-necked flask fitted with a stirrer, a condenser, an ice-cooled buret, a dropping funnel, and a thermometer. The reaction mixture is cooled to 0 and 37.5 g. (25.2 mL, 0.4 mole) nitrogen tetroxide and 0.4 mole of the olefin were added simultaneously during about 3 hours with the temperature kept below 4. The mixture is then stirred at 0 for 1.5 hrs. then slowly added to 24 ml. (0.4 mole) 70 percent (wt.) nitric acid kept at 6065 over a 1 hour period. The addition took 1.5 hrs. The mixture is kept at 60 three more hours, then diluted with water and extracted with ether followed by extraction with caustic and reacidification. Similar desirable results are obtained.

I claim:

1. The process of preparing straight chain fatty acids predominantly in the C to C range, which process is characterized by oxidizing an olefin having the formula wherein R methyl radical or straight chain alkyl radical having from about 7 to about 18 carbon atoms per radical,

R =straight chain alkyl radical having from about 7 to about 18 carbon atoms per radical,

R =H, methyl radical or straight chain alkyl radical having from about 7 to about 18 carbon atoms per radical,

with the proviso that when R is straight chain, R

is methyl,

1 l and carrying out the oxidizing with molecular oxygen,

at a temperature from 75 C. to about 110 C. whereby mainly R1, R2, R3, R1C, R20, R3C and acids are produced.

2. The process of claim 1 wherein the product acids 5 are predominantly in the C to C range and R and R individually, are straight chain allyl radicals having more than 10 but not more than 14 carbon atoms per radical and R is hydrogen.

3. The process of claim 1 wherein the product acids are predominantly in the C to C range and the R and R straight chain alkyls have more than 10 but not more than 14 carbons and R is hydrogen or a straight chain alkyl having up to 18 carbons.

12 References Cited UNITED STATES PATENTS OTHER REFERENCES Morrison et al.: Organic Chemistry (1959), page 127,

US. Cl. X.R.

P0405" UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5, 557 9 Dated January 9, 97

Inventor(s) Gene C. Robinson It is certified that error appears in the above-identified patent and that: said Letters Patent are hereby corrected as shown below:

Column 2, line 17, reads "connection", should read connected Column 5, line 65 reads "pattern, The should read pattern. The Column 6, line 65, reads "virtually as should read virtually twice as Column 8, line 19, reads "eicosesne", should read eicosene Column 11, line 7, reads "allyl", should read alkyl Signed and sealed this 15th day of June 1971.

(SEAL) Attest:

EDWARD M. LETCHER,JR. WILLIAM E. SCHUYLvlR, JR. Attesting Officer Commissioner of Patents