THE DIRECT ESTERIFICL4TION, ETC. 317

XXXIX.-The Direct Ester@xxtion of Saturated and Unsaturated Acids.

By EBEWEZER REES THOXAS and JOHN JOSEPH SUDBOROUGH.

PREVIOUS researches on the catalytic esterification of organic acids (Trans., 1898, 73, 82; 1899, 75, 467; 1904, 85, 534; 1905, 87, 1540; 1907, 91, 1033; 1908, 98, 210; 1909, 96, 315, 975) have proved that the r a k of esterification by the catalytic method is largely influenced by the constitution of the acid. Substituents in the a-positions in the acetic, succinic, and acrylic acid seriw and in the orthocposition in the benzoic series produce a retardation in the rate of esterification," and an olefine or acetylene linking in the ap-position with respect to the carboxylic group has a most pronounced inhibiting effect. An a-carbonyl group, as in pyruvic and phenylglgoxylic acids (Kailan, Mormtsh., 1907, 28, 1187 ; Sudborough, Tram. FaracFny SOC., 1912, 8), also has a retarding influence, but the effect of the ap-unsaturated linking between carbon and oxygen is not nearly so pronounced as an a/3-unsaturated linking between carbon and carbon.

Recent experiments tend to show that o-acetylbenzoic acid is eslerified more readily than benzoic acid by the catalytic method.

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318 THOMAS AND SUDBOROUGH: THE DIRECT

Numerous investigations have also been made on the rates of esterification of organic acids when the direct method is used, that is, when the acid reacts with the alcohol in the absence of a catalyst. Menschutkin ( J . pr. Chem., 1881, [ii], 24, 89; 1582, [ii], 25, 193) claimed that his results proved that in the case of aliphatic acids the introduction of alkyl groups in c l w proximity to the carboxylic group lowers the rate of esterification and also that an olefine linking produces a retardation.

Objections have been raised to some of Menschutkin’s numbers, as even during the short time (one hour) that the mixtures were heated equilibrium had been attained in several cases.

Lichty’s results for the chloroacetic acids (Amer. Chem. J., 1895, 17, 27; 1896, 18,590) prove, on the other hand, that the introduc- tion of chlorine atoms into the acetic acid molecule accelerates the direct esterification of the acid. This is exactly opposite to what is observed when the catalytic method is adopted. Sudborough and Lloyd (Trans., 1899, 75,467) and Gyr (Ber., 1908, 41, 4316) have proved that halogen substituents in the acetic acid molecule have an inhibiting effect when the catalytic method of esterification is used. Similar, but not such pronounced, differences have been met with in the case of aromatic acids (Rosanoff and Prager, J . Arner. Chem. SOC., 1908, 30, 1895; Michael and Oechslin, Ber., 1909, 42, 317), and both Rosanoff and Michael claim that their results vitiate the “ steric hindrance ” hypothesis of Victor Meyer. Michael has elaborated a view according to which the direct and catalytic methods are essentially different processes. The direct process consists in the formation of (‘ Kekul6 double molecules ’’ between acid and alcohol, then the rearrangement of the chemical

/OEt forces so that a derivative of an ortheacid, R-0-OH, is formed

\OH (Henry, Ber., 1877, 10, 2041), and finally the decomposition of this complex into ester and water owing to the better (‘ neutralisation of the atoms.” The introduction of alkyl groups into acetic acid causes a diminution in the ‘‘ free chemical energy ” of the carboxyl group; the introduction of chlorine atoms, on the other hand, increases the energy contents of the carboxyl group, and hence increases its reactivity towards alcohol. Catalytic esterification consists in the formation of a complex between the alcohol and catalyst; the (‘ double molecules ” so formed have a greater energy content tean the alcohol molecules alone, and hence can more rapidly bring about the state of maximum entropy in the acid- aloohol-catalyst system, that is, the formation of ester and water. Addition to the carbonyl group does not take place owing to the

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ESTERIFICATION OF SATURATED AND UNSATURATED ACIDS. 319

negative character of the alcohol-catalyst double molecule, but the acid is added on to the original double molecule, giving a more complex double molecule, which is directly transformed into ester, water, and catalyst. ’

Our own view is that the direct and catalytic esterification are essentially the same, the only difference being that in the former case the organic acid is its own catalyst. As the activity of the catalyst is largely a function of its strength (Goldschmidt), it follows that a strong organic acid will be esterified more rapidly than a feeble acid by the direct method unless some powerful inhibiting factor comes into play; thus di- and tri-chloroacetic acids are esterified more rapidly than acetic acid. I n none of the cases examined by Rosanoff and Prager and by Michael and Oechslin is an ortho- substituted benzoic acid esterified more rapidly than benzoic acid by the direct method, although many of them are much stronger acids. This may be due to the inhibiting effect of the or the substituents.

An interesting acid to study in this connexion would be one of the type of aa-dichloroglutaric acid, CO,H~CCl,*CH,*CH,*CO,H.

(1.1 (2.1 According to Michael’s view the carboxylic group 1 should be more readily esterified than carboxylic group 2 by the direct method, whereas by the catalytic m e t h d the carboxylic group 2 should be the more easily converted into the carbethoxy-group. According to our view, carboxyl No. 2 should be esterified more readily than No. 1 by both catalytic and direct methods, as in the direct method the function of the carboxylic group No. 1 is chiefly to act as catalyst. Our intention is to study the esterification of such acids by different methods, and to examine the acid esters formed.

Most of the results which have been obtained by the catalytic and direct methods are in harmony with the view that in both processes a t least two factors are concerned, namely, (1) the strength of the acid esterified, (2) a stereochemical factor, for example, the presence of substituting groups in close proximity to the carboxyl group. I n the direct method the first factor is of paramount importance, but the second factor comes into play especially in the aromatic series. When the catalytic method is used, the first factor is almost negligible, as the catalyst is a strong acid and completely overpowers the catitlysing influences of the carboxylic acids themselves (compare Sudborough and Feilmann, Proc., 1897, 13, 241).

The object of the experiments described in this paper has been to ascertain whether when the direct method of esterification is employed the same differences between the rates of esterification of

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320 THOMAS AND SUDBOROUGH: THE DIRECT

saburaid and unsaturated stcidEs arc3 observed aa when the catalytic method is wed. The only data, betaring on khis point are Menschut- kin's results with crotonic acid and Michael and Oechslin's m p a r i - son of crotonic and rt-butyric acids (Ber., 1909, 42, 322), which indicate that an a/3-olefine linking has a retarding effect on direct esterification.

Our method of prmdure was to heat a known weight of the acid with a large excess Df pure methyl alcohol in sealed tubes at looo for given periods of time, and to estimate the amount of ester by titrating the unesterified acid by means of standard alkali. The results we have obtained are given in the following table,

which &o gives the dissociation constants of the different acids where these are known.

Velocity constants have not been determined, as when the direct method is used in the preclence of a large excess of alcohd the ordinary equation for. a unimolmular reaction does not hold god; the values for I;: calculated from k=l/tloga/a-x diminish its t increases.

Pewentage esterified. Each number is the

mean of two experiments. Dioso- I ciation

24 72 144 constant. No. Acid. Formula. hours. hours. hours. L x lo5. 1. Cinnamic ............ CHPh:CH.CO,H ............... 2.2 7.2 13.6 3.5 2. 8-Phenylpropionic ~:H,Ph*CH,'CO,H ............ 18% 29'9 55.4 2.3 3. 67-Phenylcrotonic CHPh:CH*CH%*CO,H ...... 39 '4 65 '4 - - 4. Crotonic ........... CHMe:CH-CO,H .............. 1-4 4'2 7-4 2.0 5. n-Butyric ........... CH,Me*CH,*CO,H ............ 9.0 22% 35.7 1.5 6. isoButyric.. ......... CHMe,'CO,H .................. 7.5 19.0 30.8 1.44 7. B-EthyIacrylic ...... C!'H,Me*CH:CH'CO,H ........ 0.8 5.1 9.3 1-48 8. Ethylidenepropionic CHMe:CH*CH,'CO,H.. ....... 22.6 48'2 64-3 3-35 9. Allylacetic ......... CH2:CH'CH2'CH,'C'0,H ... 10 9 25.3 41'2 2-09

10. n-Valeric ........... CH2Me'CH,'CH2*C0,H ...... 13.0 31.0 45.7 1'58 11. B-Dimethylecrylie CMe,:CH'CO,H .... %.... ...... 0'6 1'0 2-0 - 12. imValeric ............ CHMe,*CH;UO,H ............ 4'6 10.8 19.4 1 *73 13. p-Propylacrylic ... CH,Me'CH,'CH:CH'C02H .. 3.3 8 '6 15.4 1.89 14. Hydrosorbic ......... CH,Me'CH:CH'CH,'CO,H.. 16'9 38 9 55.6 2-5 15. Sorbie ............... CHMe$H'CH:CH.CO,H ... 2'9 6-4 10.9 1.73 16. n-Hexoic ............ CH2Me'CH2*CH 'CH2*C02H 10'2 25.0 38.6 1'44 17. isoButylacetic ...... Cff Me2*CH2*Cd*C0,H ...... 10.8 25.7 39-9 1'44 18. Methyl hydrogen

maleate ............ CO,H'CH:CH*CO,Me ......... 21.8 40'9 68.2 600 19. Methyl hydrogen

snccinate ......... CO~H'CH~oGH,*C02h!Ie ...... If '3 28'4 47.3 3-3 20. Phenylpropylidene-

acetic - ............... CH&'h*CH,*CH:CH'CO,H .. 0.5 5 % -

The resulk obtained point to the following general conclusions : (1) Where the difference in the strengths of the acids is not very

marked, the a&unsaturated acid is esterifid leas readily than its saturated analogue, although, as a rule, the unsaturated acid is a

21. CinnamenyIpropionic CHPh:CH'CH,~,'CO,H.. 12.5 30.7 - -

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ESTERIFICATION OF SATURATED AND UNSATURATED ACIDS. 321

slightly stronger acid than the saturated compound (Nos. 1 and 2, 4 and 5, 7 and 1 0 , l l and 12, 13 and 16).

When the difference in the strengths of the two acids is very pronmaced, as in the case of methyl hydrogen maleate and methyl hydrogen succinate, where the unsaturated acid is nearly two hundred times as strong as its saturated analogue, the unsaturated acid reacts more readily than the saturated (Nos. 18 and 19).

(2) Acids with the olefine linking in the By-position are more readily esterified than the corresponding saturated acids (Nos. 3 and 2, 8 and 10, 14 and 16). The &-acids are, as a rule, stronger than either the saturated analopes or the &?-isomerides (compare Fichter and Pfister, A n d e n , 1904, 334, 201; FichteT and Miiller, ibid., 1906, 348, 256; Fichter and Rudin, Ber., 1904, 37, 1615; Fichter and Obladen, &a., 1909, 42, 4703). (3) W h the olefine linking is still further removed from the

carboxylic group, its effect on the rate of esterification is not marked. The two y&unsaturated acids examined (Nos. 9 and 21) we esterified at much the same rate as saturated acids.

(4) Only one acid with conjugate double linkings, one of which i s in the &position, has been examined, sorbic acid (No. 15), and in this case the effect is much the same as a simple u&double linking.

(5) Normal acids, both saturated and unsaturated, are generally more readily esterified than the isomerides containing branching chains (Nos. 5 and 6, 7 and 11, 10 and 12). When, however, this branching is not in close proximity to the carboxylic group its effect is very smaII (Nos. 16 and 17).

(6) Although an afhnsaturated acid is esterified leas readily than ib saturated analogue by the direct method, the difference is not nearly so marked as when the catalytic method is used. In the latter case the ratio is frequently 1 : 40, but using the direct method the ratio is often 1 : 4 or 1 : 5.

EXPERIKENTAL. The tubes used in the experiments were made of hard Jena-glass

1 cm. internal diameter. After thoroughly cleaning and drying, each tube was drawn out at either end, one a d was sealed and the other fitted with a rubber tube and glass plug. Each tube was fixed in a wire cage, by means of which it was suspended on the balance, and also subsequently hung in the bath. The alcohol used in all the experiments waB Kahlbaum’s No. 1 methyl alcohol, which was distilled five times over small amounts of calcium.

About 0.01 gram-m.decule of the acid was weighed out into a small flask and about one hundred and twentysix times the

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322 THOMAS AND SUDBOROUGH: THE DIRECT

theoretical weight of pure methyl alcohol added, and the weight of the solution determined. With concentrations of this type it was found that all t.he acids diasolved a t the ordinary temperature, and with such a large excess of alcohol the concentration of the alcohol caa be regarded as remaining constant. About three grams of such a solution ww transferred to each tube, and the whole weighed and then sealed.

To transfer the solution, the flask was fitted with a rubber cork carrying two tubes; the longer tube was drawn out to a fine capillary 1.5 cm. long, and the other provided with a calcium chloride tube and blow ball, so that the solution driven out of the flask ww replaced by dry air. Each tube was re-weighed, and sealed off without allowing the flame to come in contact with the open end of the tube. The tubes were placed in wire cages, and suspended from long brass rods in boiling water contained in large cans provided with reflux condensers.

I n all cases at least two determinations were made, and pre- liminary experiments showed that results agreeing to within 4 or 5 per cent. could be obt.ained. I n many caaes where it was desired to compare two acids, the tubes containing the different solutions were heated side by side for the sane length of time, so that the results are strictly comparable. The results obtained by heating a given axid solution for the same periods, but a t different times, were also in excellent agreement, so that all the results are directly comparable.

The concentration of the acid solution before heating was deter- mined by titration with barium hydroxide solution, using phenol- phthalein it& indicator. I n all cases, with the exception of volatile acids (such as butyric and valeric), the concentration determined by titration agreed with the amount weighed. With the volatile acids the actual concentration used in the calculations was that determined by titration.

After the tubes have been heated for the stated periods, they were removed, and a t once plunged into cold water. The outside of the tube was then well washed, the tube opened, and the contenh washed into a titration flask by means of neutral * rectified spirits. Freshly boiled distilled water was added, and the amount of free acid determined by titration with standard barium hydroxide sclution.

In one experiment with each of the acids, valeric, isovaleric, and

* The alcohol used was mixed with sufficient haryta water until, when mixed with water and two drops of phenolphthalein, a single further drop of alkali gave a pink coloration.

The results obtained were in most cases in good agreement.

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ESTERIFICATION OF SATURATED AND UNSATURATED ACIDS. 323

B-ethylacrylic, remarkable results were obtained. After heating the two former for seventy-two hours and the last for one hundred and f orty-f our hours, titrations indicated that almost complete esterification had taken place. These results may have been due to the presence of a minute trace of some catalyst in the tubes.

(1) Cinnnmic acid, m. p. 133*, after crystallisation from benzene.

.4. Weight of acid, 1.3036. 2.855 of solution (=O.lOll of acid) required 34.60 C.C. of

Weight of solution, 36-82.

0'0198N-barium hydroxide solution (= 0.1015 gram acid).

B. Weight of acid, 1.5330. 3-244 of solution (=0-1151 of acid) required 38.90 C.C. of

Weight of solution, 43'17.

0.0198N-barium hydroxide (= 0.1140 gram acid).

Weight of solution.

A . 2'876 3'148 3'146 3.003 2.805 3 '1 95

B. 2-761 3-166 3,674

4 in hours.

24 24 48 48 72 72 72 144 144

No. of C.C. of 0.0198N- barium hydroxide.

34-05 37 *30 35.60 34.00 31-30 35.80 31-10 32.80 38'10

Per cent. csterified.

2.3 2'2 6-6 6'6 7.9 7.6 6 *1 13'6 13'5

(2) fl-l'henylpopionic acid, m. p. 48.5-49.5O.

A . Weight of acid, 0.9770. 2.798 of solution ( =Om0980 acid) required 32-95 C.C. of 0.0198N-

Weight of solution, 27.9.

barium hydroxide solution ( = 0.0979 acid).

B . Weight of acid, 0.8100. 2.959 of solution (=0*1062 acid) required 35-60 C.C. of 0.0198W

Weight of solution, 22.55.

barium hydroxide (=0.1057 gram acid).

Weight of solution.

A. 3'051 4.152 2'891 3'284 4'373 3-752

B. 4'166 3'689

t , in hours.

24 24 48 48 72 72 144 144

NO. of C.C. of 0'0198N- barium hydroxide.

29-40 40-10 44-20 26.80 31-70 27-15 22.30 1915

Per cent. esterified. 18.3 18.1 29-0 30.8 38-5 38'6 55.6 57.1

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324 THOMAS AND SUDBOROUGH: TEE DIRECT

(3) j3y-Phcrzylcrotomic acid, m. p. 86O.

Weight of acid, 1.0162. Weight of solution, 26.26.

Weight of solution.

2.145 3'513 2.507 2'224 3-384 2-568 4-080

t, in hours.

0 24 24 48 48 72 72

No. of C.C. baryta. 25.6 25'42 18.15 12-05 18-40 10.70 16-75

Concentration of of barium

hydroxide. 0-0198N 0-0198N 0.01 98N 0-0198N 0.0198N 0-0198N 0-0198N

(4) Crotonic acid, m. p. 72O.

Weight of acid, 1-02. Weight of solution, 48-85.

Weight of solution.

3.010 3-272 2-872 3-157 3-212 4'021 4'067

Weight of solution.

4.175 2.166 4.287 4-023 2.995 2.996 3'671 4'172

No. 0Ec.c. of t , barium

in hours. hydroxide. 0 38.15

24 40-70 24 35.75 72 38'45 72 38-90

144 47 '20 144 47-80

Concentration of barium hydroxide. 0 -01905N 0.01905N 0.01905N 0-01905N 0'01905N 0 -01905N 0.01905N

(5) n-Butyric acid, b. p. 163*5O/757 mm.

t , in hours.

0 0

24 24 72 72

144 144

No, of C.C. of Concentration barium of barium

hydroxide. hydroxide. 52-00 0.01927N 27-15 0.0192TN 48'70 0'01927N 45.75 O*01927N 28 -8'0 0*01927N 28'95 a -0 1 9 2 7 . ~ 29-75 0-01927N 33.30 031927M

Per cent. esterified.

0 39 '4 39 +4 54'6 54'4 65.1 65.6

Fez, cent. estdfied.

0 1 -1 1 *7 3.9 4-4 7'4 7'3

Per cent. esterified.

0 0 9'0 9.0 23 *o 22'7 35'1 36'1

(6) isoButyric acid, b. p. 153-154*5O/765 mm.

Weight of solution.

3-216 2'466 3-698 3-073 2 '823 2.689 3 '747 3.737

t , in hours.

0 0

24 24 72 72

144 144

No. of C.C. of barium

hydroxide. 39.95 30-75 42.55 35'43 28-50 27-10 32.30 32.20

Concentration of barium hydroxide. 0-01927N 0-01927N 0 *01927N 0'01927N 0*01927Ay 0-01927s 0-01927N 0.01 927N

Per cent. esterified.

0 0 7-5 7'4

18-9 19.0 30-8 30'7

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ESTERLFICATION OF SATURATED AND UNSATURATED ACIDS. 32s

(7) &Ethylcl.cryZic Acid.

This was prepared as described in Trans., 1911, 99, 2314. No. of C.C. of Concentration

Weight of 4 barium of barium solution. in hours. hydroxide. hydroxide.

2.180 0 28'6 O'0198N 1.560 0 17'9 0-0198N 2-726 24 31-0 3-0198N 2.629 24 29.0 0.0198N 3.189 72 34.85 0-0198N 3.661 72 39'95 0.0198N 2.263 72 24-70 O.0198N 3'726 144 38'85 0'0198N 2.891 144 30'20 0 '01 98N

Per cent. esterified.

0 0 1'2 0'4 5 '1 5-2 5-1 9'4 9.3

(8 ) Ethplidenepopwnic acid, b. p. 191--192O/747 mm., was prepared from the barium s a l t (Trans., 1911, 99, 2314).

Weight of solution.

3.309 3-586 3 311 3.004 3-721 3'807 4'392 3'910

4 in hours.

0 0

24 24 72 72

144 144

No. of C.C. of Concentration barium of barium.

hydroxide. hydroxide. 38'6 0-1927N 43'4 0.193ZN 30.80 0.1927N 28-15 0-1927N 23'15 0-1927N 23.85 0*192?N 19.00 0-1 927N 16-80 0-1927N

Per oent. esterified.

0 0 32 *9 22-3 43'4 48 '1 64-1 64 '4

(9) Allybcet ic acid, b. p. 186*5-187*5°/770 mm.

Weight of solution.

2'457 1 -200 3.165 3 *866 3-217 4'288 4.216 4 '124

4 in hours.

0 0

24 72 72

144 144

a4

No. of c.c. of Concentration barium of barium

hydroxide. hydroxide. 28 -8 0 -01 98N 14.05 0.0198N 33'00 0 -01 98 N 40.35 0.0198" 27'90 O.0198N 37'85 0.01 98N 29*06 0-0198N 28 '47 0-0198N

Per cent. eshrified.

0 0

10'8 11.0 25 '9 24 *7 41 -2 41.1

(10) n-Valerie acid, b. p. 185.5-186p50/766 mm.

Weight of t , solution. in hours. 3.080 0 2.353 0 3-131 24 2-804 24 4.905 72 3,517 72 3-880 144 5.176 144

No, of C.C. of Concentration barium of barium

hydroxide. hydroxide. 37'25 0~0198N 28-55 0.0198N 32-80 0.0198N 29-65 0.0198N 41 -60 0 *ill9 8 N 28'95 0-0198N 25-80 0'0198N 34-60 0-0198N

Per cent. estmified.

0 0

13-4 12.7 30.0 32-0 45'1 44'8

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326 THOMAS AND SUDBOROUQH: THE DIRECT

(11) P-Dimethylacqlic acid, m. p. 67'8-68.3O.

Weight of t, solution. in hours. 3.668 0 3,440 24 3.443 24 3-378 72 3'744 72 1.881 144 4.374 144

No. of C.C. of barium

hydroxide. 44-60 41-50 41-70 40.70 46-10 22.50 51-90

Concentration of barium hydroxide. o-0198N 0.0198N 0 '0 19 8N 0.0198N O'0198N 0-0198N 0'0198 N

Per cent, esterified.

0 0-8 0'4 0'9 1 -0 1 '6 2.4

(12) isoValeric acid, b. p. 1 7 6 - - 1 7 6 * 5 O / 7 6 8 mm.

Weight of solution , 3'386 4-848 3.228 2.899 3'673 3.992 3.352

No. of C.C. of Concentration 4 barium of barium

in hours. hydroxide. hydroxide. 0 41-40 0'0198N 24 56-60 0*0198Ar 24 37 -60 0-0198N 72 31'60 0'0198N 72 40.10 0'0198N 144 39-35 0.0198N 144 33.05 0'0198N

Per cent. esterified.

0 4-5 4-7 10.9 10.7 19'4 19.4

(13) &Propylacrylic acid, m. p. 32.1-32'3O.

Weight of solution. 2'284 2-703 2.391 2.590 2-175 2-755 2-197

No. of C.C. of t , barium

in hours. hydroxide. 0 28-00 24 32.00 24 28-45 72 29-05 72 24'45 144 28.60 144 22.85

Concentration of barium hydroxide. 0 01965N 0-01965N 0 *01965N 0 *01965N 0.01 965N 0-01965 N 0'01985N

Per cent. esterified.

0 3 '6 3'1 8.5 8 '5 15.5 15.2

(14) Hydrosorbic acid, b. p. 102--104O/9 mm.

Weight of solution.

2.955 3.742 4'456 3 -847 4.658 3-426 3-581

4 .a75

t , in hours.

0 0 24 24 72 72 144 144

No. of C.C. of Concentration barium of barium

hydroxide. hydroxide. 58.50 0 *O 1905N 35-40 0.01905N 37.25 0.01 905N 44'55 0 *01905N 28.65 0.01905N 34-65 0-01905N 18'60 0-01905N 19'15 0 *01905N

Per cent. esterified.

0 0 17.0 16.7 37'9 38 '0 55'7 55 '4

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ESTERIFICATION OF SATURATED AND UNSATURATED ACIDS. 32'7

Weight of solution. 3.573 3.601 3.719 3.396 3.532 3-695 4'004 4-340

(15) Sorbic acid, m. p. 133-134O.

$9

in hours. 0 0 24 24 72 72 144 144

No. of C.C. of Concentration barium of barium

hydroxide. hydroxide. 44.95 0 .O 1905N 46-30 0.01905N 45'25 0 -01 905N 41-60 0 '01 905N 41-85 0 -0 1905 N 43-22 Om01905N 44.60 0 *01905 N 48.95 0 *01905N

(16) n-Hezoic acid, b. p. 202-202*5°/761

Weight of solution. 2-591 3'373 2.785 3-056 2'61 1 2.859 3.642

No. of C.C. of Concentration t, barium of barium

in hours. hydroxide. hydroxide. 0 32.35 0.01 905N 0 42-35 OwO1905 N 24 31-30 0-01905N 24 34-35 0.01905N 72 24 '45 0.01905N 72 26-95 0-01905N 144 28-00 0*01905N

Per cent, esterified,

0 0 3'2 2 '6 5.8 7.0 11 '4 10'4

mm.

Per ceat. esterified.

0 0 10'2 10'2 25-2 24 *7 38.6

(17) isoButylacetic acid, b. p. 197.5-198O/774 mm.

Weight of solution. 3.868 2.794 3.648 3.410 3.556 3.020 2'713 3.579

t, in hours.

0 0 24 24 72 72 144 144

No. of C.C. of Coucentration barium of barium

hydroxide. hydroxide. 50.72 0 -01905N 36.50 0.01905N 42.55 0-01905N 39.90 0 -01905N 34-60 0 -02905N 29-45 0 '01 905 N 21-40 0*01905AT 28 '1 0 0 '01 905N

Per cent. esterified.

0 0 10'9 10.7 25-7 25-6 39-8 40'0

(18) MetFUyL hydrogen mulea,tt (compare Trans., 1905, 87, 1844).

Weight of solution. 3'827 3.398 3.750 3.690 4.035 2'742 4.456

t, in hours.

0 0 24 24 72 72 144

No. of C.C. of barium

hydroxide. 43-15 38-25 32.95 32-55 26-75 18-80 21 .OO

Concentration of barium hydroxide. 0-0198N 0-0198N 0'0198N 0.0198N 0.01 98N 0.0198N 0Q198N

Per cent. esterified.

0 0 21'9 21-7 41.1 40-7 58 '2.

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328 HlBBEaT : THE QUANTITATIVE ESTIMATION OF HYDROXY-,

(1 9) Methyl hydrogen swciozate, m. p. 56-5-57-5O.

Weight of 8, solntion. in hours. 2-418 0 2.187 0 3'804 24 3'081 24 3 -233 72 3'618 72 3'543 144 4.421 144

No. of C.C. of barium

hydroxide. 29 -20 26'40 40'55 33-13 28-00 31-15 22.70 27.80

Concentration of barium hydroxide. 0.0198N 0.0198N 0.0198N 0 -01 98 N 0.0198N 0-0198N 0 -01 98N O.0198N

Per cent. est mified .

0 0 11-6 10.9 28 S 28-6 45-8 47 9

(20) Pheny~prop?Jlideneacetic acid, m. p. 102*5-103°. No. 0fc.c. of

Weight of 4 barium solution. in hours, hydroxide. 4.274 0 51 '60 2-789 0 33-58 2.107 24 25-10 3-310 24 39'85 3,560 72 40.50

Ccmc0ntr&tion of barium Per cent.

hydroxide. esterified. 0'01927iV 0 0 -01 927N 0 0-01927N 1 0'01927N 0 0 '01 927 N 5.5

(2 1) Cinnnmenylpropiomk acid, m. p. 89-90°.

Weight of solution. 3'281 2-406 3-127 3'272 2.677 2'578

No. of C.C. of t, barium

in hours. hydroxide. 0 39-50 0 29 -00 24 33'00 24 34-55 72 22.30 72 21 -60

Concentration of barium hydroxide. 0.01 927N 0'01927N 0 *019 27 N 0 '0 1 9 27 N 0 -0 1927lV 0'01927N

Per cent, esterified.

0 0 12'5 12'4 30'9 30-5

THE EDWARD DAVIZS LABORATORIES, UNIVBESITY COLLEGE CJF WALES,

ABERYSTWYTH.

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