alyses of these fractions by silica gel chromatography substantiated the presence of saturated hydrocarbons. A heart cut of butylene dimer fraction was prepared by distillation and analyzed by ASThI D 1159 and the modified electrometric methods. The bromine number of the fraction was 166 by the D 1159 method, compared to the theoretical value of 142. The bromine number by the modified method (142) agreed exactly with the theoretical value. Table I V gives comparative data on catalytic reformate fractions and two polpalkyl aromatics by the two methods. The modified method gives essentially constant, low bromine numbers on the reformate fractions, but the ASTM method (3) gives higher values as the molecular weight increases. These high values are probably due to substitution reactions, as indicated by the values obtained on the two aromatics: mesitylene and durene. Elimination of the iiiercuric chloride in the electrometric titration of such samples is desirable, as reported bp hlatteson ( 1 2 ) .
Results similar to Unger’s data (14) have been obtained on pure olefins. CONCLUSIONS
Considering the data on aromatics and polymers, the data on pure olefins ( 1 4 , and the types of olefins in cracked gasolines and polymers (5, IS), it is reasonable t o conclude that the modified electrometric method is more reliable than the ASTM methods for almost all types of petroleum fractions. The modified method is more accurate for highly aromatic fractions and for the di- and trisubstituted olefins that predominate in cracked naphthas and polymers. The work reported by Unger (14) supports this conclusion. ACKNOWLEDGMENT
The author wishes to thank C. C. Martin, J. W. Loveland, and S. S. Kurtz, Jr., for helpful suggestions. He is indebted t o E. W.Smith and E. I?. Jenkins for the experimental work.
LITERATURE CITED
(1) Am. SOC.Testing Materials, ‘‘ASTAI Standards on Petroleum Products and Lubricants,” Method D 101855T (1955). Ibid., D 1158-55T. Ibid., D 1159-55T. Ibid., D 1319-56T. Chem. Eng. News 33, 4113 (1955). Criddle. D. IF7.. LeTourneau. R. L.. A N A L . CHEM.’23, 1621 (1951). ’ DuBois, H. D., Skoog, D. A., Ibid., 20, 624 (1948). Francis, A. W., IND.EXG.C H E ~ I . , ANAL.ED.18, 821 (1926). Hinden, S. G., Grosse, A. V.,Ibid., 17, 767 (1945). Johnson. H. L.. Clark. R. A,. ASAL. -CHEM:19, 869 1194f): Kurtz, S. S., Jr., Mills, I. W., Martin, C. C., Harvey, W. T., Lipkin, M. R.. Zbid., 19, 175 (1947). Matteson, R.; C‘alifornia Research Corp., Box 1627, Richmond, Calif., private communication. (13) Saier, E. L., Pozefsky, Abbot, Congeshall, N. D., ANAL. CHEW 126,-i258 (1954). (14)xUnger,E. H., Ibid., 30, 375 (1958). I
RECEIVEDfor review August 3, 1957. Accepted October 26, 1957. First Delaware Valley Regional Meeting, ACS, February 16, 1956.
Influence of Olefin Structure on Bromine Number as Determined by Various Analytical Methods E. H. UNGER Research and Development laboratory, Socony Mobil Oil Co., Inc., Paulsboro, ,Three methods of determining olefins b y bromination have been critically surveyed. Two were tentative ASTM standard methods; the third was a modification of the ASTM electrqmetric titration method, which omitted the mercuric chloride catalyst from the titration solvent. Forty-five API standard olefins were analyzed, and the relationship between the structural type of olefin and bromine number was examined. Position of the double bond, extent of branching, and position of the branching affect results. In general, the modified ASTM electrometric titration method gave results closest to theoretical values. The Beckman Model KF-3 Aquameter gave reproducible, accurate values in the determination of bromine number, and was more rapid than the standard electrometric titration apparatus.
HE chemical determination of olefins in petroleum distillates is usually based on addition of a halogen to the double bond. Differences in
N. J.
rates of reaction of various types of olefins, and the tendency of halogen substitution to occur with some olefins as well as with aromatics and paraffins, have made the development of a satisfactory analytical method very difficult. Francis (6) introduced the stable aqueous potassium bromide-bromate titrant which liberates bromine in acid solution. Mulliken and Wakeman (15), Thomas, Bloch, and Hoekstra ( I ? ) , and Lewis and Bradstreet ( I d ) all studied and modified the Francis procedure. The Johnson and Clark (8) modification was adopted as a tentative standard by the American Society for Testing Materials (1), because the results on pure olefins were closer to theoretical values than those obtained by previously described procedures, This method, as pointed out by Johnson and Clark, is least satisfactory for highly branched olefins. Kaufman (9) proposed use of a solution of bromine in methanol saturated with sodium bromide as the brominating reagent. Uhrig and Levin (18) and Wilson (19) studied and modified this procedure. The modified procedures
avoid a large excess of bromine, greatly reducing the possibility of substitution reactions; however, the reagent requires frequent standardization, and end point detection is difficult rvith colored samples. To overcome these difficulties DuBois and Skoog (5) titrated the olefin electrometrically with bromide-bromate reagent. Subsequent investigation of this method by the American Society for Testing Materials confirmed that in the presence of the catalyst the method gave acceptable agreement with the color method; however, cooperative studies with a wider variety of branched olefins than had been available to the original authors showed that substitution still occurred. Nevertheless, the method was adopted as a tentative ASThI standard (9) on the basis of its agreement with the existing standard. Leisey and Grutsch (11) have recently developed a method for trace quantities of olefins, in which the olefins are titrated with coulometrically generated bromine and the end point is detected amperometrically. Wood (90) has described the determination of bromine number of olefin polymers by an electrometric titration VOL. 30, NO. 3, MARCH 1958
375
procedure similar t o the method described hcrein. The characteristic absorption of olefins in the infrared and near-infrared regions of the spectrum has been studied (10, 14, 16). The fact that olefins which are tetraalkyl substituted at the double bond-Le., in which there is no ethylenic hydrogen-do not show characteristic absorption in either region prevents development of quantitative methods. Long and Neuzil ( I S ) have developed a promising method, in which they measure the absorption of iodine complexes of olefins in the ultraviolet region of the spectrum. The author has critically surveyed the results obtained by the two ASTM methods and by a third method which is identical to the electrometric method, except that the mercuric chloride catalyst is omitted. The third method has been the subject of considerable testing in the petroleum industry. The three methods are referred to here as D 1158, D 1159, and modified D 1159. As part of this work the use of the Beckman Model KF-3 Aquameter as a n automatic titrator was investigated. There was no significant difference between the results obtained with the Aquameter and with the commonly used electrometric apparatus. The Aquameter gave accurate, reproducible bromine numbers and was much more rapid. It was used without modification; some accessory glassware was designed and fabricated to make the routine determination of bromine numbers more rapid and convenient. Forty-five standard olefins prepared by the American Petroleum Institute, Project 6, have been analyzed by the three methods, I n general, results obtained with the modified D 1159 method are closest to the theoretical values. The apparent relationship of structure to sensitivity toward conditions of bromination is discussed in detail below.
titration solvent. I n this JTork ethylene glycol and water precooled with dry ice was used. The drain a t the bottom of the titration vessel makes it unnecessary to raise the buret assembly after each titration. When only occasional samples are to be analyzed, the regular titration vessel may be placed in an ice bath. However, more samples may be titrated in a given time by using jacketed apparatus.
PROCEDURE
Figure 1. Accessory glassware for Aquameter
The standard electrometric titration apparatus, equipped with a magic eye ( 2 ) was used in the experiments which compared the Aquameter with the standard ASTM method.
APPARATUS
Frediani ('7) described an automatic titrator for use with Karl Fischer reagent, the Beckman Model KF-3 Aquameter (manufactured by Beckman Instruments, Inc.). This instrument was used without changes; however, the KO. 1843 electrode (band type) was used, as the newer No. 19031 electrode (inlay button type) does not have sufficient sensitivity. A satisfactory electrode was also made from two squares of platinum foil, inch square, sealed in parallel through glass, similar to conductivity cell electrodes. As the titration is carried out a t reduced temperature, 0" to 5" C., a jacketed titration vessel and automatic pipet were designed (Figure 1). A suitable refrigerant, circulated through the jackets, maintains the required temperature and precools the next batch of
376
ANALYTICAL CHEMISTRY
pare 1 liter of titration solvent by mixing 712 ml. of glacial acetic acid, 134 ml. of carbon tetrachloride, 134 ml. of methanol, and 18 ml. of sulfuric acid (1 t o 5). STANDARDOLEFINS. Olefins prepared by the American Petroleum Institute, Project 6, were used throughout. The sample size and the procedure for \\-eighingand diluting the olefins with carbon tetrachloride were as specified ( 2 )*
Standard ASTM Electrometric Titration. Procedure D 1159 ( 2 ) was used, except t h a t the bromide-bromate solution was 0.25W instead of 0.59. Automatic Titration. Operation of the Aquameter is checked (3). The titration vessel and automatic pipet are cooled with circulating refrigerant. Titration solvent from the self-leveling automatic pipet (110 =I= 10 ml.) is drained into the titration vessel; when the temperature of the solvent has reached 0" to 5" C., a blank titration is performed in the standard manner, using a polarizing current of 10 pa. and a standby period of 30 seconds. When the blank titration is completed, an appropriate aliquot of the sample is added and the titration procedure repeated. Khen the modified solvent (omitting the mercuric chloride) is used, the polarizing current is set a t 5 pa. and the timer a t 60 seconds. Color-Indicator Titration. The procedure and calculations of D 1158 ( 1 ) were used. Calculations. The bromine number is defined as the number of grams of bromine consumed by 100 grams of the sample reacting under given conditions. I n D 1159, the blank is determined separately and a correction made in the calculation. I n the automatic titration method, the solvent is pretitrated, thus eliminating any blank value from the calculation. I. Bromine number D 1159 ( 2 ) : Bromine number
=
( A - B ) LJ' X 7.99
w
11. Bromine number for automatic titration : All reagents except carbon ,tetrachloride were analytical grade chemicals. A X N X 7.99 Bromine number = STANDARD BROMIDE-BROMATE SOLUwTION ( 0 . 2 5 N ) . Dissolve 51.0 grams of where potassium bromide and 13.92 grams of potassium bromate in water and dilute -4 = ml. of bromide-bromate soluto 2 liters, Standardize in the usual tion used for titration of TTay against 0.1N sodium thiosulfate sample solution ( 2 ) . B = nil. of bromide-bromate soluTitration Solvent A. WITH MERtion used for titration of CURIC CHLORIDE CATALYST.Prepare blank 1 liter of titration solvent by mixing S = normality of bromide-bromate 714 ml. of glacial acetic acid, 134 ml. solution of carbon tetrachloride, 116 ml. of T f = grams of sample used methanol, 18 ml. of sulfuric acid (1 t o 5), and 18 ml. of a methanol solution of mercuric chloride (100 grams RESULTS A N D DISCUSSION per liter). Use of Aquameter for Automatic Titration Solvent B. WITHOVT Titration. I n a preliminary study, to MERCURIC CHLORIDE CATALYST. PreREAGENTS
Table I.
Sample 2-Methyl-trans-3-hexene 3-Methyl-2-ethyl-1-butene ZJ5-Dirnethyl-2-hexene 2,3-Dimethyl-Z-butene 2,3-Dimethyl-l-butene 2-Ethyl-1-butene
4,4-Dimethyl-trans-2-pentene
1-Methylcyclohexene 1-Heptene Cyclohexene Diisobutene ' Purified by silica gel percolation.
Comparison of Electric Eye Titrimeter and Beckman KF-3 Titrator
BPI No. 1058 1059 1060 540 589 538 574 1040 520 (I
a
determine if the Beckman Model KF-3 Aquameter would be suitable for the bromine number determination, nine A P I standard olefins and two olefins purified by silica gel percolation were analyzed (Table I). These samples were titrated by both the electric eye apparatus (2) and the Aquameter. Both the ASTilI electrometric solvent and the modified solvent (containing no mercuric chloride) were used in the titration of each sample. Duplicate titration results, typical of those obtained on the two pieces of electrometric apparatus, are included in Table I for the titrations with the modified solvent. To determine if the Aquameter would work equally well with samples encountered in routine operation, ten petroleum samples from a n ASTM cooperative program, analyzed previously by another operator using the ASTM electrometric apparatus, were run on the Aquameter (Table 11). I n both studies there was no significant difference between the values obtained with the Aquameter and the ASTR'I apparatus. Sensitivity of Olefins toward Conditions of Bromination. Forty-five standard olefins were analyzed by the three methods: 41 mono-olefins and four diolefins. Because of the great deviation of three of the four diolefins from the theoretical values, the results nere averaged separately for the mono-olefins and diolefins (Table 111). OLCFIS TYPES.Mono-olefins have bern classified into five types representing the extent of alkyl substitution at the carbon-carbon double bond (4).
I. H .>C=C
C=C
H R ,Rl
R '2
111. H
H
2R'
(API standard samples) D 1159 Theory ASTM KF-3 163 172 170 163 224 225 142 147 150 190 209 207 190 216 212 190 163 163 163 195 142 144 144
1-Olefins, nionoalkyl substituted at double bond 1-Olefins, dialkyl substituted at double bond Other than l-olefins, monoalkyl substituted on both carbons of double bond
Table II.
Duplicate Titrations, ASTM 162.0 161.5 164.1 161.8 143.2 141.8 192.3 190.8 195.6 196.5 195.7 194.0 182.7 179.4 161.8 167.9 137.3 130.9 197.6 196.8 143.7 144.6
Mod. D 1159 KF-3 161.5 162.9 161.1 158.0 142.2 139.8 192.3 190.8 196.5 191.1 196.6 201.1 180.0 179.4 159.1 161.1 136.6 139.2 194.9 195.5 144.1 142.9
Comparison of Electric Eye Titrimeter and Beckman KF-3 Titrator
ASTM No. 1A
1B 2.A
(ASTM cooperative samples) D 1159 Method ASTM KF-3 Sample Debut. cat. reformate 2.8 2.7 2.9 2.6 Depent. cat. reformate 2.8 2.8 2.8 2.8 Debut. comm. gasoline 15.7 18.3 15.8 18.6 Depent. comm. gasoline 17.6 17.2 17.3 17.1 Depent. cat. crkd. gasoline 40.4 40.4 40.4 40.6 Depent. therm. ref. gasoline 42.8 42.8 42.8 43.1 Depent. str. run naphtha 0.1 0
Mod. D 1159" ASTM KF-3 2.0 1.9 2.0 2.1 2.1 2.2 2.1 13.1
13.0 2B 14.4 14.4 3 35.9 36.0 4 35.9 36.0 5 0.1 0.1 0 0.2 6 Kerosine 2.3 2.6 1.5 2.3 2.8 1.5 7 Jet fuel (JP-5) 1.5 1.7 0.6 1.3 1.7 0.6 8 Depent. comm. gasoline 26.5 26.0 22.1 26.2 25.8 22.3 Similar to D 1159, but with HgClz catalyst omitted from titration solvent.
IV. H
Ri
16.3
15.1 15.1
36.3 36.4 38.4 38.5 0 0 1.5 1.5
0.4 0.5 22.9 22.7
/Rz Other than l-ole-
fins, trialkyl substituted at double bond R, Other than l-olefins, tetraalkyl substituted at R 'd double bond
\R,
1'.
16.0
Table 111. Percentage Deviations from Theoretical Bromine Numbers
Method
By thus classifying the mono-olefins, it is possible t o explain the results ob-
Mod Sample D 1158 D 1159 D 1159 41 monoolefins, yo 9 05 + l 0 . 5 - 0.64 4 diolefins, ?2 -34.3 -33.3 -38 9
tained by the various bromine number methods (Tables IV t o VIII). Type I olefins gave nearly theoretical results by the color-indicator method (D 1158). The average deviation was +2.49% for 10 samples (Table IV). The greatest deviation in the group was +6.84y0 for 3,3-dimethyl-l-butene. This olefin has a double branch at carbon 3, which is as close t o carbon 1 as branching can occur in Type I olefins. The molecule is also highly unsymmetrical about the double bond. The standard electrometric method (D 1159) showed a deviation of +5.96%
for the 10 Type I mono-olefins; the biggest deviation again was for 3,3-dimethyl-1-butene, With the modified electrometric method, the average deviation was -11.5%. Apparently this type of olefin reacted slowly in the absence of mercuric chloride and the reaction was not complete when the 30-second end point was reached. In an effort to bring these results closer to the theoretical values, the standby period was lengthened t o 1 minute by changing
>=C/
R2
+
VOL. 30,
NO. 3, MARCH 1958
377
Olmi
m 0
4
8
%
I2
16
20
24
D E V I A T I O N FROM T H E O R Y - D
28
32
1158
Figure 2. Correlation of calculated reactivity constant with deviation of ASTM D 1158-57T from theoretical bromine number
the setting on the Timer disk of the Aquameter. When this was done, the average deviation for the 1-olefins decreased to -4.190/& I n neither titration did 3,3dimethyl-l-butene show abnormal behavior. Increasing the standby period to 1 minute had no effect on any of the titrations with the solvent containing the catalyst. I n the titrations which omitted the catalyst, only the results on Type I olefins and naphthenes with unsaturated side chains were affected significantly by the change in standby period and these were improved. On this basis, a 1-minute standby period is recommended. Type I1 olefins are dialkyl substituted on one carbon of the double bond, making these molecules all unsymmetrical about the double bond. The D 1158 results on six of these olefins had a n average deviation of +24.2% (Table V). The largest deviations were given by 3-methyl-2-ethyl-l-b~tene and 2-ethyl-1-butene, indicating that a larger substituent group near the double bond tends to increase the bromine substitution reaction. D 1159 showed a n average deviation of +20.8%, the same two olefins giving the highest results. By the modified method, the average deviation from the theoretical results was only -0.37%. Type I11 olefins are monoalkyl substituted on both carbons of the double bond. Eleven Type 111 olefins had a +3.06y0 average deviation from theoretical when analyzed by D 1158, +8.99% by D 1159, and +0.07% by the modified method (Table VI). Type I V olefins are trialkyl substituted a t the double bond, leading to very unsymmetrical molecules. Seven Type IV olefins by D 1158 gave an average deviation of +13,4% (Table VII). The greatest deviation waa in 3-ethylZpentene, which had a +25,8% devia-
378 *
ANALYTICAL CHEMISTRY
tion, showing again the effect of the larger substituent group. Results obtained by D 1159 showed a n average deviation of + l l . O % ; by the modified method, only +0.22% deviation. Type V olefins are tetraalkyl substituted a t the double bond. This type is the most highly branched olefin at the double bond, but the branching can be such that the molecule is completely symmetrical about the double bond, as is the case with 2,3-dimethyl-2butene. Only two Type V olefins (Table VII) were titrated, and these showed average deviations of +10,6% for D 1158, +9.67% for D 1159, and +0.62% for modified D 1159. Two other types of mono-olefins were analyzed (Table VIII). One was a naphthene with a n unsaturated side chain, these could be considered Type I olefins with branching on the third carbon. The results on two of these olefins were similar to those of Type I olefins. The other type was cyclic olefins; four were analyzed. They showed deviations of +12.3% by D 1158, +10.3% by D 1159, and +1.41% by the modified D 1159. Four standard API diolefins were also analyzed (Table IX). For the three compounds having the two double bonds on a single carbon atom or in a conjugated system, the results were 40 to 50% low; this indicated that only slightly more than one double bond was brominated. This was true for all three methods, although the color indicator results mere slightly higher than the others. However, with l,5hexadiene, in which the double bonds are separated by four carbon atoms and are located on the terminal carbons, the reaction was very similar to that of a Type I olefin. Obviously, the interpretation of bromine numbers for samples of high diolefin content is difficult-
Table V.
API So.
Sample Theory 2-Ethyl-1-butene 538 190 2-Methyl-1-pentene 530 190 2-Methyl-1-hexene 1025 163 2,3-Dimethyl-l-butene 539 190 3-Methyl-2-ethyl-1-butene 1059 163 2,3,3-Trimethyl-l-butene 550 163 Average 176.5
of API Type II Olefins D 1158 D 1159 Dev. % dev. Found Dev. % dev. +56 $46 +29.47 236 $24.21 f17.89 +34 +27 +14.21 217 1-28 4-17.17 +19 f11.66 182 1-48 $25.26 220 $30 1-15.79 +54 $33.13 +6l +37.42 224 +36 $22.09 198 $35 +21.47 $42.6 +24.17 212.8 t 3 6 . 3 +20.79
Bromine Numbers
Found 246 224 191 238 217 199 219.2
Table VI.
Sample
API No.
trans-2-pent me 283 526 cis-2-Hexene 527 trans-2-Hexene 1006 trans-2-Heptene cis-3-Hexene 528 trans-3-Heptene 1015 548 trans-40ctene Branched 4-?*lethyl-trans-2-pentene 536 4-Methyl-cis-2-pentene 537 4,4-Dimethyl-cis-2-pentene 582
228 190 190 163 190 163 142
235 194 193 165 192 169 151
190 190 163 163 179
4,4Dimethyl-trans-2-pent-
ene
Bromine Numbers of Type 111 Olefins
D 1158 Dev. yo dev.
Theory Found
Unbranched
574
hverage
+4 $3 1 2 $2
+9
+1.21 $1 05 +3 68 $6 34
199 195 163
+9
+4.74
+9 0
$2.63 0
175 185
$12 +5.36
+7.36
+6
2,2-Dimethyl-trans-3-hexe ‘ne
Type
Y Olefins
2J-Dimethyl-2-butene 2,3-Dimethyl-2-hexene
KO, Theory Found
1060 1058
1017 Average 540
1028 .Iverage
particularly if both conjugated and nonconjugated types are present. Effect of Oxygen, Sulfur, and Nitrogen Compounds on Bromine Number. Bromine numbers should be viewed Lvith t h e greatest suspicion when appreciable amounts of sulfur, nitrogen, and oxygen compounds are present in t h e sample. T h e author h a s done some preliminary work t h a t shows t h a t phenol, thiophene, and some amines all yield lower bromine numbers in t h e modified D 1159 than in either the D 1158 or D 1159 methods. o-Thiocresol, on the other hand, reacted more readily in the absence of the mercuric chloride catalyst than in its presence. Correlation of Structure with Reactivity toward Excess Bromine. i i n attempt was made t o correlate structure with the deviations from theoretical results when t h e pure monoolefins were analyzed b y t h e color-
f3.06
Found
D 1159 Dev. % dev.
Found
166
$12 9 +24
+
+ 3.68 + 9.47 + 4.90 32 ++ 56 52 +14 46
235 189 189 163 193 163 149
206 206 175
+16 +16 +12
+ 8.42 ++ 8.42 7.36
188 188 159
193 195
+30 +16.1
+18.40 8.99
158 180
253 197 208 171 202 I72
+25
+11.96
+7 +18 +8
+
Mod. D 1159 Dev. 70 dev. $2.98 -0.53 -0.53
+7 -1 -1 0
0
+ I .58
13
$7
0 +4 93
-2 -2
-1.05 -1.05 -2.45
0
-4 -5
-3.07
$0.18
+O.Oi
Bromine Numbers of Type IV and V Olefins
Table VII.
533 286 1012 535
$2.98 +2.11 +1 58
+i
API
Sample Type IV olefins 2-Methyl-2-pentene 2-Methyl-2-butene 3-E thyl-2-pentene 3-Methyl-trans-2-pentene 2,5-Dimethyl-2-hexene 2-Methyl-trans-3-hexene
Mod. D 1159 Found Dev. 70dev. 198 +8 $4.21 182 -8 -4.21 161 -2 -1.23 194 +4 +2.11 160 -3 -1.84 161 -2 -1.23 176.0 -0.50 -0.37
190 228 163 190 142 163 142 174.0
212 260 205 220 161 169
190 142
202 163 182.5
166.0
156
197.6
D 1158 Dev. % dev. Found $22 $32 42 30 +I9
$11.58 +14.04 +25.77 f15.79 +13.38 3.68 9.86 $13.44
++ + 6 ++ ++23.57 14 1-12 +21 +16.5
202 248 193 208 149 171 176 192.4
+12 +20 $30 +I8
++ 78 +34
+18.43
++14.78 6.32
208 +18 156 +14 +10.55 182.0 +16.0
indicator method. Four main structural features were considered: 1. Difference in number of carbon atoms on each side of the double bond. This was least significant in straightchain 1-olefins. 2. Number of branches on the straight chain. 3. Proximity of the branch to the double bond. 4. Absence of any ethylenic hydrogene at the double bond.
These four features were assigned arbitrary numerical values and a “reactivity constant” was calculated by means of the following equation: Reactivity constant = KR=D+ B + P - S - H where:
D
D 1159 Mod. D 1159 Dev. % dev. Found Dev. % dev.
= difference between number of
carbon atoms on each side of double bond B = number of branches on straight chain
+ 6.32 + 8.77 +18.40 9.47 +++ 4.93 4.91 +23.94 +10.96
190 235 165 191 142 161 139 174.7
+ 9.86 9.47 + 9.67
191 $1 143 +1 167.0 +1.0
$
P
0 +7 +2 +1
$3.07 +1.23 +O. 53
-2 -3 $0.71
-1.23 -2.11 $0.21
0
0
0
+O ,53 +OJO +O .62
= proximity factor. Each carbon
atom in each branched chain following values : 10. Branch directly on double bond 2. Branch one carbon removed from double bond 0.4. Branch two carbons removed from double bond 0.1. Branch three carbons removed from double bond S = No. of carbon atoms in molecule/$ for straight-chain 1-olefins only H = 10 when no ethylenic hydrogen is attached to either carbon at double bond (Type V olefins)
is assigned the
The reactivity constant obtained was plotted against the per cent deviation of the bromine number (1) from the theoretical value (Figure 2). A reasonably straight line can be drawn passing close t o the origin. This is VOL. 30, NO. 3, MARCH 1958
379
or-*
??? ON0
+I
3
m
09N. ?
I
++ +
0
ccr: .t
9 3 7 . 3 4
+I
m 3
033:
I
i
0 m g :. r-.
++ +
m
b
strictly an empirical evaluation and is presented mainly to show the possibility of correlating structure Kith reactivity. There was not nearly so good a correlation between this constant and the D 1159 results; this indicates that the olefins reacted in a different manner when a catalyst was present than when there was a large excess of bromine. CONCLUSION
On the basis of these studies, it is concluded that the modified electrometric method, which omits the catalyst, is the best for determining olefinic unsaturation in hydrocarbon mixtures by bromine addition. If a n automatic titrator of the type described is used, a 1-minute standby period is preferable to the 30-second period ( 2 ) . ACKNOWLEDGMENT
The author wishes to thank E. T. Scafe, 0. I. Milner, John Herman, and R. J. Zahner for helpful advice in the preparation of this paper. ul
&m
LITERATURE CITED
6
(1) Am. SOC.Testing lIaterials, Designa-
-0 Y-
O L ul
a,
Q
5
Z
.-Em
2
m
?i m Q
+0
tion D 1158-57T. . ~ ~ . ~~ .~ . . (2) Ibid., D 1159-57T. (3) Beckman Instruments, Inc., Bull. 369. Boord, C. E., “Science of Petroleum,” Vol. 11, p. 1353, Oxford University Press, London. 1938. DuBois, H. D., Skoog, D. .4., ASAL. CHEJI.20, 624 (1948). Francis, A. W.,Ind. Eng. Chem. 18, 821 (1926). Frediani, H. A,, ANAL. CHEJI. 24, 1126 (1952). Johnson, H. L., Clark, R. A., ANAL.CHEU.19, 869 (1947). Kaufman, H. P., 2. Unterszich. Lebensm. 51, 3 (1926). Lauer, J. L., Rosenbaum, E. J., A p p l . Spectroscopy 6,29 (1952). Leisey, F. A., Grutsch, J. F., AYAL. CHEW28, 1553 (1956). Lewis, J. B., Bradstreet, R. B., I ~ D ENG. . CHEW, A x . 4 ~ . ED. 1 2 , 3 8 7 (1940). Long, D. R., Neuzil, R. T.,AYAL. CHERI. 27, 1110 (1955). Mcllurry, €I L., . Thornton, V , Ibid., 24, 318 (1952). Nulliken, S. P., IVakeman, R. I... ISD. EYG. CHEV., ASAL. ED. 7, 59 (19351. Saier, E. L., Pozefsky, -4bbot, Coggeshall, S . D., SAL. CHEX 26, 1259 (1954). Thomas, C. L., Bloch, H. S., Hoebstra, J., IND.EYG.CHCJI.,A x ~ L . ED.10, 153 (1?38). Uhrig, K., Levin, H., I b z d , 13, 90 (1941). Wilson, G. E., J . Inst. Petroleum 36, 25 (1950). Wood, J. C. S., ANAL.CHEY.30, 372 (1958). ~
RECEIVEDfor review June 10, 1957. Accepted Sovember 26, 1957. Group Session on Analytical Research, 22nd Midyear Meeting, Division of Refining, American Petroleum Institute, Philadelphia, Pa., RIay 1957.
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