A C T A U N I V E R S I T A T I S L O D Z I E N S I S FOLIA CHIMICA 4. 1935
Mirosława deka. Maksymilian Ignaczat
CEROMĘTRIC DETERMINATION OF IMENuL ANO SOME OF ITS DERIVATIVES
A method has been developed of determining phenol and its de rivatives using cerium perchlorate in aqueous perchloric acid so lution, Tha procedure takes advantage of the kinetic method of fixed reaction time and of the amperometlc method of determining the amount of reacted cerium (IV).
Oxidation of phenols with various oxidizers has received a lot of attention. In most cases the process is held to be non- stoichiometric. The end products are mostly ring derivatives of the compounds studied, usually their mixtures which are difficult to separate and identify [1-5]. The present study is part of a larger investigation devoted to oxidation of phenols with ce rium perchlorate in perchloric acid medium. Cerium perchlorate exhibits high oxidizing potential (1.71 V) and its other proper ties include high stability of its solutions and the fact that perchlorate end cerium ions do not form complexes junction [6]» It has been found that cerium (IV) in Hulo^ solution oxidi^us phenol and its derivativ«s in a destructive way. and the re sults of 8toichiometric measurements show that It can be used
for quantitative determination of these compounds.
Experimental
Reagents and solutions
3 3
Solution of cerium perchlorate 1 mole/dm in 2 wole/dm per chloric acid was prepared in accordance with S m i t h and G e t z [7]. Cerium perchlorate concentration was determined by the amperometrIc roathod using titrated sodium oxalate solution [&]. The concentration of perchloric acid in cerium perchi-orat«
so-lution was determined alkacimetrically with cerium (IV) ha ving first bean reduced to cerium (III);
Sodium oxalate solution - 0.05 mole/do»“' Perchloric acid solution - 9.5 wole/dm
Aqueous solution of phenol, p-cresol, p-nitrophenol, p-hydro- xybonzolc acid and picric acid - lO*^ mole/dm .
2 ,6-dinitrophenol solution - 6.25 x 10 ^ mole/dm
The phenols usud were purified by distillation (phenol and p-creaol), crystalization fro* water (p-nitrophenol, p-hydroxy- benzoic acid), or fro* dilute acid (2,6-dinitrophenol and picric acid). The water employed had bean distilled twice.
Procedure
5 miuole cerium perchlorste were introduced into the measuring flask together *ith an amount of perchloric acid such that its concentration in the reaction medium was 2 mole/dm1 . Water was added to the solution and, after appropriate temperature had been obtained in the thermostat, a specified quantity of the solution of the reducing agent was added (Tab. 1). The volume of the reaction mixture was 0.1 m1 . The time of the reaction was deter mined experimentally. Samples of the reaction mixture were taken
in which the reaction was stopped by adding 10 ml of 005 nole/dm sodium oxalate solution. The excess of unreacted sodium oxalate was .titrated back with cerium perchlorate solutionj the equiva lent point of titration was determined by the amparómetrie method with no external e.m.f applied [8]. The quantity of cerium (IV) rthich had reacted with the appropriate reducing agent correapon- ded In this case to the number of mmoles of cerium perchlorate u~ sed for titration of the unreacted sodium oxalate. The oxidation process was regarded as completed when the quantity of unreacted ceriuf} (XV) did not change even though the reaction was allowed to continue. Threa series of measurements were made for each phe« nol studied. The results obtained and the statistic« are pre sented in Tab. 1.
Discussion
The measurements performed show that complete oxidation of phenol and its derivativas with cerium (IV) in perchloric acid
Statistical evaluation of the results of determination of phenol and soae its derivatives with ceriusi perchlorate as the oxidizer
■... Oetenaind compound Reaction t ime Tempera ture K Amount used mg Mean obtained
X mg
Mean relative error SO for indivi dual re sults 5 mg Signifi cance interval of the mean -*0.95’8 ■9 sr . 100.
A t 1 2 3 4 5 6 7 8 9 phenol 60 343 5.00 8.00 10.00 4.96 7.97 9.93 -0.80 -0.13 -0.70 0.015 0.077 0.028 0.016 0.080 0.029 0.12 0.04 0.11 p-creeol 120 343 7.24 12.00 16.36 7.21 11.95 16.31 -0.41 -0.42 -0.31 0.080 0.030 0.076 0.084 0.031 0.080 0.44 0.10 0.19 p-nitrophenol 120 343 6.00 9.00 12.OC 5.95 6.89 11.91 -0.83 -0.11 -0.75 0.047 0.0063 0.084 0.049 0.0067 0.088 0.32 0.029 0.29 p-hydroksy- benzoic acid 120 343 2.76 4.14 8.28 2.77 4.08 S.14 0.36 -1.45 -1.69 0.040 0.023 0.089 0.042 0.024 0.093 0.61 . 0.23 0.44 2,6-dinitro-phenol 5.75 8.63 11.50 5.73 8.56 11.42 -G .35 -0.81 -0.70 0.053 0.083 0.11 0.056 0.087 0.12 0.38 0.40 ' 0.40 picric acid 10 293 4.58 6.87 9.16 4.54 6.82 9.09 -0.87 -0.73 -0.76 0.059 0.022 0.10 0.063 0.023 0.11 0.52 0.13 0.18solution doe# not taka place with satisfactory rate until the temperature i* raised. It wss found in earlier research that tne rates of these reaction are U n i t e d by the dxidation processes involving the intermediate compound [9], The only exception is picric acid which undergoer oxidation at room temperature, the rate of the process being detgrained by the transfer of the first electron [10]. The end products of this reaction are carbon dio- xide and formic acid detected in the reaction «tedium by quali tative tests. It -is noteworthy that formic acid does not unde rgo oxidation with cerium (XV) under the conditions and during the time of the present measurements [11-13]. Its presence was confirmed by chromatography; the chromatographs of the ether ex tract« of the poetreact ion mixture» corresponded to that of the standard HCOOH - sample.
Measurements were also performed of the quantity of carbon dioxide given off in the different oxidation reactions. On the basis of the results obtained the following reaction schemes can be proposed for the oxidation of phenol end its derivatives.with cerium (IV) in perchloric acid solution»
CgH .OH 26CaiU + H H 20-^5C02 + HCOOH + 26Ce3+ ♦ 26H*
H3C - C&H 4 - OH ♦ 24Ce4^. ♦ 13H20 - ~ 2 C 0 2 ♦ 5HCGGH ♦ 24Ce3 * -> 24H*
02N - C6H4 - UH ♦ 24Ce4 * ♦ 1 2 ^ 0 4C02 ♦ 2HC00H ♦ 24Ce3+ + 25H*
+ m 3~
.H4 - OH ♦ 24Ce4 * ♦. H H g O — 5C02 ♦ 2HC00H ♦ 24Ce3* ♦ 24H*
C6H3 ~ 0H + 22Ce4+ ♦ ISHjO 3C02 + 3HCOOH ♦ 22Ce3 * ♦ ♦ 24H* ♦ 2N03"
C6H2 ’ 0H ♦ 20Ce4+ ♦ 14H2 0-*-2C02 + 4HCOOH ♦ 20Ce3 * «• ♦ 23H+ ♦ 3N03~
In post cases the results of the determinations collected in Tab. 1 involve small negative relative error. This is probably due to partial oxidation of the compounds studied under the in HOOC - C,
6
(u2Nl2
-fluence of light ond atmospheric oxygen. Considering the amounts of the substances uawd for da terminations, the magnitudes of mean relative error may bo regarded as virtually negligible. The small relative standard deviation valu«3 testify to the accuracy of the method proposed. It is simple, does not require the use of any sophisticated apparatus, and permits comparatively accurate da~ terminations of the compounds involved.
References
[1] G e i n C. A., O. Am. Chem. Soc., 71, 407 (1949).
[2] S h i b o s v a 6. T .. M a \ e 1 i t z a L . W ., Kinetika i Katallz. 6. 782 (1961).
[ 3 J G i n s b u r g Vi. D.. 2hur. Fiz. Khim., 33. 1504 (1969). [4j B e h r ro a n £. 0.. 3. Am. Chem. Soc«. 05. 3478 (1963). [5] G o r b a c h e v s . V., S o r o k i n I . N . , Zhur. Fiz.
Knin.. 33. 702 (1969).
[6] H a r d w i c k T . 3 . , H o b e r t u o n E., Canad. 0. Chem., 29, 018 (1951).
[7j S m i t h G . F . . G e t z C., Ind. fcng. Chom. Anal. Ed., 12. 339 (1940). i 8 ] M i c h a l s k i £.. C z a r n e c k 1 K . , Chom. Anal.. 4. 85 (i959). [9] I g n a c z a k M., U e k a M .. Pol. 3. Chem., 54. 259, (1930). [ 10] I g n a c z a k M., O e k a M., Pol. 0. Chem., 56. 229, (1982).
[11] M i c h a l s k i E . , I g n a c z a k M.. Soc. Sci. Lodz. Acta Chim., 13, 35 (1968).
C12] K h a n I., B o s e S., Indian 3. Appi. Chem.. 30, 48 (1967).
[l3] K a n s a l B. 0.. S i n g H.. Indian Chem. Soc., 55. 618 (1978).
Department of General and Inorganic Chemistry Institute of Chemistry
Mirosława Doka, Maksymilian Ignaczak
CERUMETRYCZNE OZNACZENIE FENOLU I NIEKTÓRYCH 3 EGO POCHOONYCH
Opracowano aetodę oznaczania fenolu i Jago pochodnych przy użyciu nadchloranu cerowego w wodnym roztworze kwasu nadchlorowe go. Wykorzystano w tym celu kinetyczny metod? ustalonego czasu reakcji oraz motod? amperometryczne do określenia ilości prze- reagowanego ceru (IV;.
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