June 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
Soap extraction is sometimc,s complicated by water absorption by the specimen or by poor emulsification, as previously discussed. For these reasons rub-off data are believed t o reflect more accuratelv the diffusion moperties of plasticizers. As shown by Quackenbos, the diffusion constant of a plasticizer may be calculated from the exposcd area of the specimen, the initial plasticizer concentration, the weight loss, and the time of exposure. For most formulation problems, however, the K value determined on the compound a t hand provides a more direct indication of service behavior. A knowledge of plasticizer concentration is not necessary for the calculation of K value.
- -
1349
assisted in obtaining the data shown herein and in preparing this paper. The exploratory work of R. H. Lindh on the rub-off test and the suggestions of H. M. Quackenbos on interpretation of data have been especially helpful. REFERENCES
Barrer, R. M., “Diffusion in and through Solids,” 1st ed., pp. 216 ff , New York, NIacmillan Co., 1941. Geenty, 3. R., India Rubber W o r l d , 126, 646-9 (August 1952). Haward, R. N., Analyst, 68, 303-5 (1943). Hopke, E. R., and Sears, G. W., J . Chem. Phys., 19, 134551 (1951).
PRECISION OF TESTS
A statistical analysis of replicated test data by several operators, over an extended period of time and involving several oompounds, has been made to permit a valid estimation of th6 test reproducibility. Data of 27 oil-extraction, 60 rub-off, and 60 soapy water-extraction tests were analyzed. On the basis of theqe measurements over-all test precisions of 3 ~ 1 5 ,&16, and *37% were obtained for the proposed oil-extraction, rub-off, and soapy water-extraction tests, respectively, a t the 95% certainty level.
Liebhafsky, H. il., Marshall, 4 . L., and Verhoek, F. H., IND. ENG.CHEM., 34, 704-8 (1942). Parks, G. S., and hloore, G. E., J . Chem. Phgs., 17, 1151-3 (1949).
Perry, J. W., “Chemical Engineers’ Handbook,” 3rd ed., pp. 538, 545, Xew York, McGraw-Hill Book Co., 1950. Reed, AI. C.,and Harding, J., ISD. ENC.CHmr., 41, 675-84 (1949).
Schulz, E. F., A S T M BUZZ.,183, 75-8 iJuly 1952). Small, P. -4., J . SOC.Chem. Ind.,66, 17-19 (1947). Small, P. A,, Small, K. W., and Cowley, P., Trans.Faradau SOC.,44, 810-16 (1948).
Verhoek, F. H., and Marshall, 8. I,., J . Am. Cliein. SOC.,61,
ACKNOWLEDGMENT
2737-42 (1939).
The authors wish to express their appreciation to the others of the Development Department of -Bakelite co., who have
R E C E I V E D for
review June 30,1953
. ~ C C E P T E D Deceiiibei
5 , 1953.
Relation of Molecular Structure to Detergency of Some Alkylbenzene Sulfonates F. N. BAUMGARTNER ESSO
Laboratories, Standard Oil Development C o . , Linden, N. J .
T
H E chemistry of surface active agents has had widespread development during the past decade. The present investigation is concerned with the effect of molecular structure on the surface active properties of alkyl-benzene sulfonates. For this purpose a series of eleven sodium dodecylbenzene sulfonate isomers and homologs was used. These compounds are represented by the generic formula
RIikeska, Smith, and Lieber (6). A modification of the sulfonation procedure of Leiserson, Bost, and Le Baron (3) was used to prepare the sodium sulfonates. The entire sequence of preparations is Lidicated as follows:
0 ;!
+ Ar H AlC13 --+R
RCCl
p
.4r
R-CH-R’ 0
‘USO&a where R is an alkyl group and R ’ is hydrogen or an alkyl group. The detersive ability, surface tension, and wetting power were determined. Measurements were made in aqueous media on the sulfonates both in the pure form and in the presence of sodium sulfate.
OH
I
The secondary alkylbenzenes were prepared most conveniently by the procedure of Gilman and Meals ( I ) . The n-alkylbenzenes were prepared using the modified Clemmenson reduction of
HI
--
kr
PREPARATION OF SODIUM SULFONATES
R-CH-R’
i
.4r
P
+ R-CH-R’
R-C-R’ I
(3)
Ar
SO3 NaOH R-CH-R’
SO2
I
.Ir-SO,n‘a
(4)
INDUSTRIAL AND ENGINEERING CHEMISTRY
1350
TABLE I. PROPERTIES OF A Coniimund 1-Phenyldecane 3-Phenylundecane 4-Plienylundecane
B,.P.,
Pressi.re,
131
hlm. 2.3
c.
101 105
0 2
0.23
?o
n D
1.4881 1 4861 1.4839
A
~
~
Calod. 7cH 88.00 12.00 87.86 12.11 87.86 12 1-1
%C
~
7
~
,
~
Found % C %El 88.21 11.91 87.72 1 2 30 87.77 12.04
Vol. 46, No. 6
Several of thr sodium sulforiat,es were v e r y ~insoluble ~ ~ in ~ice ~water ~ and s could be obtained in crystalline form. They m r c recovered directly from the cold aqueous solution and recrystallizcd from water. .Inal?-s:>s ol thrac crystalline sulfonates are shown in Tablt. 11. EVALUATIQK OF DETERSTYE ABILITY
A wide diversity of opinion cuiat,s as t o the best method or methods ior evaluating dctemive 3-Phenyltridccane 133 0 3 1.4868 8 7 . 6 3 12 37 87.75 12.43 ability in the laboratory. I n general, in the 4-Thenyltridecane 127 0 3 1.4820 87.63 12 37 87.50 12 i i small Ecale laborator:- wishing tests no direct quant,itative relatiowllip n i t h actual homv or commercial washing- cxists. Hon-ever, for tlie During several preparations of the carbinol (2b) appreciable purpose of the p r c s m T the st:iridiird Launder-Om amounts of olefinic by-product m r c fornied by dehydration. In technique I ~ considered S these instances, a eccond reduction ITas pcJrformed using sodium parisons. and alcohol. The physical constants of the nlkylbenzenes preThe dctergcncy values reported lii,rc v\-:?re dcicrniined usiri pared in the present n.orl; are shown in Table I. As it n'as desired t o test the sulfonates not only in mixture n-ith sodium d f a t e , but also in the pure form, sulfonation TTas carried out using d f u r trioxide nitli liquid sulfur dioxide as dilueiit and coolant. This reagcnt !vas found to react subs1antially quantitntively n-ith thc dk~-lhenzenee, Thus the use of a inolo-mole r;xtio of this sulfonating agcnt t o alkylate gave, on neutralization, n practically pure sodium sulfonate. A typical sulfonation cxpcriillclir WEEcarried oiit as follows: X solution of 0.1 molc of sulfur trioxidc (Suli'an B) a n d 50 mi. of liquid sulfur dioxide n-as ndded o ~ e Rr period o f 10 iniiiutes t o olved in 230 ml. of li tirred vigorously du usted so tliat a vigorous reflux was -as coinplctc, the mixture was stirred a n additional 30 ininut(1s. The temperature remained a t -8" C. during the enfire reaction pciriod. The condenser n'as then removed and the 3ulfur ide al!on-ed to evaporate. Final traces were removed h y uating the reaction flask. The product x-as poured into icc, r and neutralized vith 507a sodium hj-droxide t o a faint Brilliant Yellow end point. The product TWS diluted t o t.ii-ice its volume vvith isopropyl alcohol and extracted tlirce times n-ith small portions of petroleum ether. The solution was dehydrared by addition of sodium carbonate at 45' to 50' C. until the carbonate no longer dksolved. After cooling, the alcohol layer Ti-as separated and evaporated t o give the pure sodiuni sulfonate. S o attempt n-as made to separate the ortho, meta, and para isomers.
~.
X-P H E N Y L DODE CCNE 40% ACTIVE DISTILLED 'WATER 120'F
cloth after washing vias meawred n-ith a Huntcr Ilultipurpo reflcctonietcr. For each jarj the avc:agc of eight r e f l e ~ t ~ ~ ~ i
1-Phenyldecane 3-Phenvlundecane
10.00 9.59 9.20 9.20 9 20 8.84
9.08 9.40
9.23 9.13
8 98 8.01
SODIUM S dLFONA TE
1
i-80
J
>
2
60
LT J -
0
-
40
J
20
I
c5
Figure 1.
Effect of Molecular Structure on Detergency
Figure 2.
I0 15 CO I CEYTRATI O N k T % ACTIVE I NG RECI EYTS
Effect ~f Sodium Sulfate
20
June 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
1351
readings, two on each side of each swatch, was used in determining soil removal. The most serious deficiency of this method is the inability to duplicate results on successive runs. In order to minimize this limitation, a standard detergent, a commercial sodium lauryl sulfate, was used as a reference. Each Launder-Ometer run included a sample of this detergent a t 0.2% active ingrrdicnt concentration in 240 p.p.m. haid water. Soil removal was then arbitrarily defined as the ratio of reflectance for the swatches washed in the test samples t o that for the standard times 100. Blank determinations were made for each run and all results were corrected accordingly. The sodium alkylbenzene sulfonates were evaluated as wetting agents on the basis of their sinking times as determined by the canvas disk test ( 2 ) . Surface tension measurements were made with a du Nouy tensiometer ( 2 ) .
0 06 W T % ACTIVE I NG REDI ENTS 40% ACTIVE 120' F
100
I-
-1
DISCUSSION
For an isomeric series of sodium dodecylbenzene sulfonates where the alkyl group consists of a straight chain, maximum detersive power is attained when the benzene ring is located on the third alkyl carbon atom. As shown in Figure 1, the differences in detersive power become less pronounced as the concentration of detergent is increased. The concentration a t which detersive power begins t o appear increases as the benzene ring is moved toward the center of the alkyl chain. This effect is shown in Table 111. The solubility of the compounds in water likewise increases. The first threc members of the series were actually isolated from Fater in crystalline form. These relatively insoluble members begin to exhibit detersive powers in very dilute solutions. Once this critical concentration is exceeded, however, the detersive powers of all members rise rapidly and approach a common maximum. The exception to this occurs with the first member of the series, the sodium sulfonate of I-phenyldodecane, the maximum of which is somewhat less than the others. This compound has a rather loa. water solubility. Consequently, its ultimate cleansing ability is limited by its solubility, as only the material actually in solution or colloidal suspension can act as a detergent.
TABLE 111. EFFECT OF POSITIOX OF BENZEXE RING (100% active ingiedients, distilled water a t lZOo F.) Concn. Required to Obtain Soil Removal Value of 10, Sodium Sulfonate Wt .% 1-Phenyldodecane
