J. P. NELSON, L. E. PETERSON, and
A. J.
MlLUN
Central Research laboratories, General Mills, Inc., Minneapolis, Minn.
b A simple method is presented for determining total nonamines in high molecular weight fatty amines. An isopropyl alcohol solution OF the amine is passed through a column of sulfonic acid ion exchange resin in the acid form. The amine is retained by the column, whereas the nonamines pass through and are weighed after evaporation of the column eluafe. Also described are procedures in which this ion exchange resin technique has been used as a preliminary separation step for determining certain nonamine .constituents by infrared spectroscopy. The infrared methods include the determination of fatty nitrile, unsubstituted fatty amide, N-alkyl fatty amide, and N-alkyl acetamide. MOLECULAR WEIUHT fatty amines have attained widespread and varied commercial usage in such areas as beneficiation of ores, corrosion inhibition, and textile conditioning. Depending upon the production procedure, these amines may contain small amounts of nonamine constituents whose concentration it is desirable to control during manufacture. In the well known process of preparing amines from fatty acids via the intermediate nitrile, the nonamine constituents may include some of the so-called unmponifiables from the fatty acid, fatty nitrile, unsubstituted fatty amide, and N-alkyl fatty amide. Figure 1 is a typical infrared spectrum of a carbon tetrachloride solution containing the nonamines separated from a high molecular weight fatty primary amine by passage through a column of sulfonic acid ion exchange resin. Absorptions are seen a t 4.43 microns for nitrile, at 5.73 microns for ester, a t 5.82 microns for acid and around 5.91 microns for unsubstituted and monosubstituted amides. Myers (a) has described a method for determining the nonamines in several high molecular weight primary amines and primary amine acetates. His method depends upon the benzene insolubility of the p r h a r y amine oxalate and thus would appear to be limited in scope. The procedure also is somewhat lengthy, requiring a titration of the reIGN
1
o
A ~ A ~ Y ~ ICHEMISTRY C A ~
covered nonamines to correct for the solubility of amine oxalates. Cation exchange resins and aqueous media have been suggested for separating cationic surfactants from anionics and nonionics (1, 8). Also, Watkins and Walton (4, have studied the cation exchange resin absorption of several low molecular weight amines from aqueous and nonaqueous solutions. In this laboratory sulfonic acid cation exchange resin has been employed for some time in the convenient separation of nonbasic constituents from high molecular weight fatty amines in organic solvent media. Based on this principle, a procedure for determining total nonamines in a variety of amines derived from Cls and Cle fatty acids has been worked out. The method has been applied to fatty primary, difatty secondary, dimethyl fatty tertiary, methyl. difatty tertiary, and fatty aminopropyl type amines. Samples in isopropyl alcohol solution are passed through sulfonic acid ion exchange resin columns, and the evaporated eluate residues are weighed as total nonamines. Described below also are methods illustrating how this ion exchange resin technique can be used for concentrating specific nonamines for accurate measurement of their concentration by infrared spectroscopy. One such application is the determination of nitrile in octadecylamine. Another is the analysis
P
of dodecylamine for unsubstituted and monosubstituted amide. A third application is the determination of ace& amide in octadecylamine acetate. EXPERIMENTAL
Reagent and Apparatus. Ion exchange resin, Dowex 50W-X4, 60- to 100-mesh, J. T. Baker Chemical Co. reagent grade. One-pound batches of the resin were washed repeatedly on a Buchner funnel with a total of 2 liters of isopropyl alcohol (reagent grade) The washed resin was covered with isopropyl alcohol and used within 3 days, or rewashed again if stored €or longer periods. ION EXCHAXGE COLUMNS.Bulbs, 500-ml. capacity with 24/40 T joints, were sealed on top of chromatographic tubes (Scientific Glass Apparatus Co. Catalog No. JC-236OII) leaving a 19mm. internal diameter section 20 cm. long. A fritted-glass disk inside a 19/22 T joint was held by springs in the bottom of the column as a support for the resin. Approximately 1 om. of glass wool was placed on top of the fritted-glass disk and a slurry of washed resin in isopropyl alcohol was poured into the column to give a 19-cm. column of resin after settling. The resin column was kept covered with isopropyl alcohol throughout. Amino propylamines required longer columns, 50 cm. in length and packed with 45 cm. of resin. STAXDARD SAMPLESFOR INFRARED CALIBRATION.Conimercial octadecyl nitrile was distilled through a PodbielI
60-
WAVE LENGTH, rnlcrons
spectrum of nonamines rsm high molecular weight primary amine
niak Heli-Grid column. Dodecylamide was prepared from dodecanoic acid and ammonia and recrystallized from carbon tetrachloride, acetone, and ethyl alcohol, map. 102.5-103' C. N-dodecyll dodecylamide was made from dodecanoic acid and dodecylamine, followed by recrystallization from petroleum ether and methanol, m.p. 78.579' C. N-octadecyl acetamide, from octadecylamine and acetic anhydride, was recrvstallized from ethvl alcohol. m.D. 80-80.5' C. Procedure. I n a 150-ml. beaker dissolve 5 grams of sample (2.5 grams for aminopropylamines) with 75 ml. of isopropyl alcohol, warming, if necessary, to obtain solution. With a pipet, remove the excess isopropyl alcohol from the top of the resin column. Transfer the sample solution onto the column, without disrupting the column packing and rinse the beaker onto the column with a minimum of warm isopropyl alcohol. Place a 1-liter beaker under the column to collect the eluate. In the case of saturated difatty secondary amines, the application of heat is necessary to maintain the sample in solution until all the solution has entered the resin column. This was conveniently accomplished by suspending the glass column through the top half of a heating mantle which was connected into a Variac. After the sample solution has run down to the top of the resin, add 500 ml. of isopropyl alcohol to the column bulb. When sufficient eluate has run out, add an a,dditional 200 ml. of isopropyl alcohol. A flow rate of 250 to 300 ml. per hour is normally experienced; however, flow rate is not critical. Collect eluate until the flow stops and evaporate to a volume of approximately 75 ml. on a steam bath with a jet of clean air. Transfer the remaining solution to a weighed 15O-ml. beaker, complet,e the steam bath evaporation, and place the residue in a 70" C. vacuum oven for 2 hours. B,eweigh the beaker, taking the weight of the residue as the nonamines. I
.
DISCUSSION
This procedure for total nonamines is not recommended for amines based on fatty moieties less than hexadecyl. These lower molecular weight products are subject to losses of material during evaporation of the isopropyl alcohol. The resin exhibited a substantially smaller capacity for fatty aminopropylamines as compared with the other fatty amines. As a result, smaller samples and longer columns were required with the fatty aminopropylamines. Table I lists nonamine values obtained during duplicate determinations on a series of commercial fatty amines. All the nonamines were checked for the presence of amine by titration in isopropyl alcohol with hydrochloric acid also in isopropyl alcohol. No amine was found in any of the samples.
Fatty nitriles exhibit specific but relatively weak absorption in the infrared at 4.45 microns and, therefore, are difficult to measure accurately by infrared when present in amines at low concentrations. The method for nonamines, however, is capable of concentrating the nitrile so that accurate determinations of nitrile are possible by infrared analysis of the nonamines. This was accomplished by dissolvhg the nonamines in exactly 5 ml. of chloroform and determining the absorptivity a t 4.45 microns in a 1-mm. cell against chloroform. The nitrile concentration was calculated in the usual manner from this absorptivity and that of a similar solution containing a known concentration of a standard fatty nitrile. This standard absorp tivity was determined us. chloroform a t 4.45 microns on a solution containing 0.10 gram of standard nitrile in 10 ml. of chloroform. On the Beckman IR4 with a speed of 0.2 micron per minute, period 2 seconds, gain 3%, and slit schedule 2X standard, 0.100 gram of octadecylnitrile in exactly 10 ml. of chloroform gave an absorptivity of 0.112 liter per gram em. (above base line) in a 0.984mm. cell. Table I1 lists results obtained with various amines and mixtures of amines with added octadecylnitrile. Employing this same ion exchange column technique followed by infrared measurement, it was possible to determine small amounts of unsubstituted amide and N-alkyl monosubstituted amide in commercial dodecylamine. These nonamine constituents were nonvolatile under the conditions employed for evaporating column eluates. Nonamines were dissolved in 10 ml. of chloroform and scanned from 5.4 to 6.2 microns in a 1-mm. (nominal) cell against chloroform. To eliminate the 6.25-micron water absorption, chloroform was dispensed from a bottle equipped with an Ascarite tube. Scans were carried out on the Becknian IR4 spectrophotometer a t a speed of 0.08 micron per minute, period 8 seconds, gain 3% and slit schedule 2X standard. Absorptivities were
T a b l e 111.
Sample 1 2 3 4
5
determined a t 5.92 microns (peak maximum of dodecylamide) and 6.01 microns (peak maximum of N-dodecyl
Table
1.
N o n a m i n e s in Commercial Fatty Amines Nonamines, Primary Amine % Hexadecylamine 2.7, 2.7 Hexadecylamine, distilled 2.4, 2 . 5 Octadecylamine 3 . 9 , 4.0 Octadecylamine, distilled 1. 7 , 2.0 Octadecenylamine 1 . 8 , 1.8 Octadecenylamine, distilled 1 . 3 , 1.4 Soyamine 3.8, 3.8 Soyamine, distilled 3.8, 3.8 Tallowamine 3.3, 3 0 Tallowamine, distilled 1.7, 1.94 Hydrogenated tallowamine 3 . O , 3 . 1 Cottonseed amine 4.0, 4.1 Cottonseed amine acetate" 4.0 4 . li Secondary Amine Dihexadecylamine 0 9, 0.9 Ditallowamine 1.8, 1 6 Dihydrogennted tallowamine 2 . 9 , 2 9 Dioctadecenylamine 1.3, 1.4 Tallowaminopropylamine I .2, 1 . 2 Tertiary Amine Dimethy ltallowamine 0.7, 0.7 Sample of cottonseed amine in isopropyl alcohol solution was neutralized with acetic acid. Q
T a b l e 11.
Determination of Nitrile in Amines Nitrile, 7' DeterSample Added mined0 Tallowamine, purified 0.4 0.3 Tallowamine, distilled ... 0.5 Tallowamine, distilled 0.9 0.8 Tallowamine, distilled 5 2 5.0 Dihydrogenated tallowamine ,.. 0 . 3 Dihydrogenated tallowamine 2.1 1.8 Tallowamine, commercial . . . 1.8 Tallowamine, commercia1 distilled ,.. 1.1 Hydrogenated tallow... 4.0 amine, commercial 5 Values for samples containing added nitrile have been corrected for nitrile originally present.
Determination of Unsubstituted a n d Substituted A m i d e in Dodecylamine" Dodecylamide, yo A'-Dodecyl Dodecylamide, yo Added Determinedb Added Determinedb 0.08 None 0.04 0.20 0.27 None 0.02 0.40 0.63 Xone -0.02 0.80 0.14 0.20 0.25 0.20 0.24 0.40 0.46 0.40
a Commercial, distilled dodecylamioe analyzing 0.14 dodecylamide and 0.267, N dodecyl dodecylamide by proposed method. * Values corrected for the original amide content of the dodecylamine.
VOL. 33, NO. 13, DECEMBER 1961
0
1
Table IV. Determination of N-Alkyl Acetamide In Amine Acetates
N-Octadecyl Acetamide, % DeterAdded mined6
Sample Tallowamine acetate, lab. prep. 0.6 0.6 Tallowamine acetate, lab. prep. 3.9 3.8 Tallowamine acetate, lab. prep. 9.1 9.1 Tallowamine acetate, commercial-1 . . . 0.4 Tsllowamine acetate, commercial-1 1.1 1.6 Tallowamine acetate, commercial-2 ... 1 . 0 Tallowamine acetate, commercial-3 .., 1 . 4 Tallowamine acetate, commercial.-4 1.7 e Values for samples containing added N-octadecyl acetamide corrected for amide originally present.
...
dodecylamide) Absorptivities for solutions containing 2 grams per liter of dodecylamide were 2.81 liter per gramom. a t 5.92 microns and 0.990 liter per gram cm. a t 6.01 microns in a nominal 1-mm. cell. The same concentration
of pure N-dodecyl dodecylamide gave absorptivities of 0.520 liter per gramcm. a t 5.92 microns and 1.24 liter per gram-cm. a t 6.01 microns. Simultaneous equations were employed in the usual manner to calculate the percentage of each type of amide. Table 111 lists recovery data for synthetic mixtures of dodecylamine, dodecylamide, and N-dodecyl dodecylamide. Primary amine acetate, another commercially available fatty nitrogen derivative, is prepared by neutralizing primary fatty amine with acetic acid. A possible by-product of this neutralization is N-alkylacetamide. The ion exchange-infrared method also was applied to the determination of small amounts of this acetamide in tallowamine acetates. For this determination the nonamines from the ion exchange column were dissolved in 10 ml. of chloroform and the solution was scanned from 5.4 to 6.2 microns in a nominal 1-mm. cell against chloroform. The Beckman IR3 was employed a t settings of 5% gain, 0.3 micron per minute speed and w Csecond period. The absorptivity a t 5.97 microns was determined and the percentage of Nalkylacetamide was calculated from the absorptivity of purified N-octadecyl
Alk
olyrner Distri Condensates
tion in
Determination o
onomer through Te
acetamide, which was 1.741iterper gramcm. Appropriate correction was applied for any unsubstituted amide and N-alkyl alkylamide in the amine used for preparing the acetate. This was accomplished by carrying a sample of the amine through the same procedure and correcting for the 5.97-micron absorption of its nonamines. Table IV lists results by this method on a series of amine acetate samples. ACKNOWLEDGMENT
The authors gratefully acknowledge the work of Barbara Polister, Wesley Tolberg, and Dolores Bell, who contributed to various phases of the work reported herein. LITERATURE CITED
(1) Barber, A., Chinnick, C. C. T., Lincoln, P. A., Analyst 81, 18 (1956). (2) Killheffer, J. V., Jungermann, Eric, ANAL.CHEM.32, 1178 (1960). (3) Myers, R. T., Ohio J . Sci. 58, 34 ( 1958). (4) Watkins, S. R., Walton, H. F., Anal. Chzm. Acta 24,334 (1961).
RECEIVED for review July 3, 1961. Accepted October 5 1961. Paper No. 275 Journal Series, bentral Research Laboratories, General Mills, Inc.
yethylene
MARY ELLEN PUTHOFF and J. H. BENEDICT Procter and Gamble Co., lvorydale Technical Cenfer, Cincinnati, Ohio
b A new method that separates and quantitatively determines components containing one to four ethylene oxide units in surface active alkyl ether polyoxyethylene polymers is presented. The samples are reacted with p phenylazobenzoyl chloride and the resulting esters are chromatographed on alumina. The individual components are eluted with solvents of increasing polarity and the amount is determined gravimetrically. The combined standard deviation for the method is 1 .270b.Samples examined contained a wide range of components, including 10 to 40% of unreacted fatty alcohol. The oxyethylene distribution in the samples examined does not follow the expected Poisson distribution. 1884
ANALYTICU. CHEMISTRY
A
ether polyoxyethylene polymers produced by the condensation of fatty alcohols and 1 to 100 moles of ethylene oxide are widely used as surface active agents. The low molecular weight polymers that contain an average of 1 to 5 moles of oxyethylene exhibit good emulsifying and wetting properties. Since these condensation products consist of a broad range of molecular weights, ' knowledge of the polymer distribution is needed to correlate performance with composition. The reported procedures for determining the total polymer content (S, 8-10) do not show the distribution of the species. Only molecular distillation (6, 7) has been used to separate and to determine the various oxyethylene species present in conLKYL
densation products. However, this technique requires considerable time and is not suitable for routine analysis. Kelly and Greenwald (6) used chromatography on silica gel to separate the species containing two to 13 oxyethylene units in an octylphenol polyoxyethylene product, Silica gel chromatography of alkyl ether polyoxyethylene polymers did not give complete resolution of the low molecular weight components. Also, the Kelly and Greenwald separation requires several liters of solvent and long elution time for each sample; therefore, a new procedure was developed which involves chromatography of esterified polymers. This paper presents a method for the rapid, routine determination 'of the oxyethylene distribution in alkyl poly-
