SovietRxiv

Rate of Oxidation of Monocarboxylic Acids of the Saturated Series by Potassium Permanganate under Various Conditions

V. V. TRONOV, M. T. YALOVAYA, and K. Ya. BUDANOVA.
Submitted 1935 | SovietRxiv: ru-193501.07669 | Translated from Russian

Abstract Generated abstract

The study examines how molecular size, branching, and reaction medium affect the oxidation of saturated monocarboxylic acids by potassium permanganate. Reaction rates were measured titrimetrically for acids from formic through decanoic acid, including several branched isomers, in neutral salt solutions, alkaline media, free acid solutions, and strongly acidic media. The data indicate that, apart from formic acid, oxidation is generally faster in acidic solution and slower in the presence of excess alkali, and that rates in the normal homologous series tend to increase with chain length. Branched acids containing tertiary carbon centers oxidize more readily than comparable normal acids, suggesting weaker or more reactive carbon hydrogen bonds at such positions.

Full Text

V. V. TRONOV, M. T. YALOVAYA, and K. Ya. BUDANOVA.

RATE OF OXIDATION OF MONOCARBOXYLIC ACIDS OF THE SATURATED SERIES BY POTASSIUM PERMANGANATE UNDER VARIOUS CONDITIONS.

The principal aim of the present work was to elucidate the dependence of the oxidizability of acids on the size and structure of the molecule.

The action on organic acids of various oxidizing agents, and especially of potassium permanganate, has already been studied by many authors from the qualitative side, i.e., the products formed in such oxidation have been studied.¹) As a general conclusion, it may be noted that the hydrocarbon unit adjacent to the carboxyl is most readily subjected to oxidation. Thus isobutyric acid with an alkaline solution of permanganate gives α-oxyisobutyric acid;²) in other cases (with chromic acid), acetone was obtained from it,³) evidently with the intermediate formation of the same oxyisobutyric acid:

\[ (\mathrm{CH_3})_2\mathrm{CH}\cdot\mathrm{COOH} \ \xrightarrow{+\,O}\ (\mathrm{CH_3})_2\mathrm{C}{-}\mathrm{COOH} \ \xrightarrow{+\,O}\ (\mathrm{CH_3})_2\mathrm{C}{=}O+\mathrm{CO_2}+\mathrm{H_2O} \]
\[ \hspace{7.8em}\bigg|\qquad \]
\[ \hspace{7.8em}\mathrm{OH} \]

Acids of normal structure, as far as can be judged from the literature data,⁴) also give, with permanganate, predominantly α-oxy acids as the first oxidation products. But at the same time other \(\mathrm{CH_2}\) groups are also oxidized, and in isovaleric acid, where there is a tertiary unit in the β-position, it is oxidized even more readily than the \(\mathrm{CH_2}\) group nearest to the carboxyl group.⁵)

The mechanism of the oxidation reaction of acids differs greatly depending on the nature of the oxidizing agent employed. Under the action, for example, of hydrogen peroxide on acetic acid, it was found⁶) that the hydroxyl group of the acid reacts first:

\[ \mathrm{CH_3{-}C{-}OH}+\mathrm{H_2O_2} \longrightarrow \mathrm{CH_3{-}C{-}O{-}OH}+\mathrm{H_2O}, \]
\[ \hspace{3.1em}\bigg\|\hspace{9.7em}\bigg\| \]
\[ \hspace{3.1em}O\hspace{9.7em}O \]

1) Beilstein’s Handbuch der org. Chemie. Information on the corresponding acids.
2) R. Meyer, L. A. 219, 240—241 (1883).
3) A. N. Popov, Zh. R. Kh. O. 2, 310 (1870).
4) E. S. Przheval’skii, Zh. R. Kh. O. 45, 902 (1913).
5) W. Müller, L. A. 200, 274 (1880).
6) W. H. Hatcher, Chem. Zbl. 1927, II, 2050—52.

and then rearrangement into glycolic acid already occurs:

\[ \mathrm{ CH_3{-}C(=O){-}O{-}OH \;\longrightarrow\; CH_2OH{-}C(=O){-}OH }, \]

with subsequent rather rapid oxidation of the latter.

The work of our laboratory on the study of the action of various oxidizing agents on alcohols led to the conclusion\(^1\) that, in the reaction with chromic anhydride, the hydroxyl hydrogen is also split off first of all:

\[ \begin{aligned} &\mathrm{ CH_3{-}CH_2OH + O{=}Cr(=O){=}O \;\longrightarrow\; CH_3{-}C(H)_2{-}O{-}Cr(=O)(OH){=}O } \\[4pt] &\mathrm{ \;\longrightarrow\; CH_3{-}C(=O)H + H{-}Cr(=O)(OH){=}O \;\longrightarrow\; CH_3{-}CH{=}O + H_2O + CrO_2 } \end{aligned} \]

Potassium permanganate in an alkaline medium, on the contrary, acts at once on the hydrocarbon unit, replacing its hydrogen by hydroxyl:

\[ \begin{aligned} &\mathrm{ CH_3{-}C(H)_2{-}OH + 2\,HO{-}Mn(=O)(OK)_2 \;\longrightarrow\; CH_3{-}C(H)(OH){-}OH } \\ &\mathrm{ \qquad\qquad + 2\,KO{-}Mn(=O)(OK){-}O + H_2O } \end{aligned} \]

The aldehyde formed, of course, is still more readily oxidized further to the acid. Potassium permanganate in acid solution is, in the type of its action, close to \(CrO_3\). A neutral \(KMnO_4\) solution approaches an alkaline one.

Thus, of the oxidizing agents studied by us, \(KMnO_4\) in an alkaline medium is the most direct means of determining the strength of the bond of carbon with hydrogen. In application to the acids of the homologous series, with this oxidizing agent we shall have a determination of the strength of the \(C\)–\(H\) bond in the unit adjacent to \(COOH\).

Being interested mainly in precisely this aspect of the question,

\(^1\) V. V. Tronov and A. A. Lukavin. Zh. R. Kh. O. 60, 181–191 (1928).

we measured the rate of action of \(KMnO_4\) in the presence of alkali on the following acids:

1) \(HCOOH\).

2) \(CH_3 \cdot COOH\).

3) \(CH_3 \cdot CH_2COOH\).

4) \(CH_3CH_2CH_2 \cdot COOH\),

5)
\[ \begin{gathered} CH_3—CH—COOH.\\ \phantom{CH_3—}\vert\\ \phantom{CH_3—}CH_3 \end{gathered} \]

6) \(CH_3 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot COOH\).

7)
\[ \begin{gathered} CH_3—CH—CH_2 \cdot COOH\\ \phantom{CH_3—}\vert\\ \phantom{CH_3—}CH_3 \end{gathered} \]

8) \(CH_3 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot COOH\).

9)
\[ \begin{gathered} CH_3 \cdot CH_2—CH—COOH.\\ \phantom{CH_3 \cdot CH_2—}\vert\\ \phantom{CH_3 \cdot CH_2—}CH_2—CH_3. \end{gathered} \]

10) \(CH_3 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot COOH\).

11) \(CH_3 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot COOH\).

12) \(CH_3 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot CH_2 \cdot COOH\).

In general, the series of acids of normal structure from \(CH_2O_2\) to \(C_{10}H_{20}O_2\) has been covered almost completely (except for \(C_7H_{15}COOH\)), as well as three acids with a branched chain. For formic, acetic, butyric, isobutyric, and isovaleric acids, oxidation experiments were also carried out in a neutral medium (the potassium salt of the acid), with the free acid, and in a strongly acidic medium (addition of sulfuric acid).

In the literature there is a detailed investigation1 of the oxidation of formic acid by permanganate, and indications had been given2 of the very difficult oxidizability of acetic acid. As for the other acids of this series, no quantitative determinations of the rate of action of this oxidizing agent had been made with them (only the oxidation of ammonium salts of acids by hydrogen peroxide has been studied in more detail3).

For the most part we used Kahlbaum preparations, which were distilled before the experiments. For the less readily available acids, fractions with boiling points within a range of two degrees were taken. All reacting components (acid, oxidizing agent, alkali, and \(H_2SO_4\), where the latter were used) were employed at a concentration of 0.1 mole per liter (in the reacting mixture), except in two specially noted cases. Oxidation was carried out at ordinary temperature \((17^\circ—22^\circ)\), which of course reduced the accuracy of the determinations. At definite intervals of time samples of the solutions were taken, in which the remaining oxidizing agent was titrated with hyposulfite (after addition of \(KI\) and \(HCl\)).

In the following tables (Nos. 1—45) the results of measuring the reaction rate are presented. For some acids, in addition,

numbers obtained by different observers (K. Ya. Budanova and M. T. Yalova), with different preparations and under several different temperature conditions. Naturally, the difference in such cases was greater than for a single observer.

Oxidation in alkaline solution (R·COOK + KOH).

1. HCOOH. Conc. 0.1 gram-mol. per liter.

0.28 m. 0.61 1.03 2 4 7
Duration of experiment in min. 0.28 m. 0.61 1.03 2 4 7
Percent of oxygen that reacted 20.9 29.87 35.27 36.84 39.02 40.76

2. HCOOH. Conc. 0.1 gram-mol. per liter.

0.033 m 0.083 0.117 0.166 0.25 0.33 0.417 0.5
Duration of experiment in min. 0.033 m 0.083 0.117 0.166 0.25 0.33 0.417 0.5
In percent 2.14 5.71 6.43 7.14 9.28 10 13.57 17.85
Duration of experiment in min. 0.583 0.667 0.833 1 1.5 2 3 4 5 7
In percent 19.28 20 22.14 22.84 26.42 29.28 33.57 36.42 38.57 40.7

3. CH₃COOH. Conc. 0.1 gram-mol. per liter.

15 m 30 m 1 h. 24 h. 168 h. 2520 h. 2784 h.
Duration of experiments 15 m 30 m 1 h. 24 h. 168 h. 2520 h. 2784 h.
In percent 1.83 1.83 2.75 3.22 4.59 2.7 5.7
Duration of experiments 3048 h. 3312 h. 3504 h. 3600 h.
In percent 5.7 6.6 8.3 8.3

4. CH₃COOH. Concentration of CH₃COOK and KOH = 1 N

In 158 days, 8 percent reacted.

5. CH₃·CH₂·COOH. Conc. 0.1 gram-mol. per liter.

3 h. 24 h. 72 h. 95 h. 120 h. 192 h. 264 h.
Duration of experiment 3 h. 24 h. 72 h. 95 h. 120 h. 192 h. 264 h.
Percent (I experiment) 0.43 1.30 4.76 5.19 5.62 8.65 12.55
Percent (II experiment) 0.43 1.30 3.9 5.19 5.62 8.65 12.55
528 h. 672 h. 816 h. 1008 1320 1561 1801
Duration of experiment 528 h. 672 h. 816 h. 1008 1320 1561 1801
Percent (I experiment) 22.51 26.66 31.60 34.63 38.52 41.12 47.25
Percent (II experiment) 22.51 26.66 31.34 34.63 38.96 41.12 45.45
2089 h. 2359 h. 2959 h.
Duration of experiment 2089 h. 2359 h. 2959 h.
Percent (I experiment) 50.38 52.81 54.45
Percent (II experiment) 48.74 50.47 54.11

6. CH₃·CH₂·COOH. Conc. 0.1

15 m. 30 m. 1 h. 24 h. 96 h. 144 h. 240 h.
Time 15 m. 30 m. 1 h. 24 h. 96 h. 144 h. 240 h.
Percent 3.67 4.59 4.59 5.7 6.42 9.1 11.92
Time 288 h. 384 h. 456 h. 504 h. 528 h. 648 h. 1176 h.
Percent 15.0 15.83 18.3 23.3 29.03 30.64 31.7
Time 2496 h. 2760 2856 2928 3072 h. 3420 h. 3312 h.
Percent 52.8 54.5 57.8 58.6 60.8 61.6 61.6

7. CH·CH₂·COOH. Concentration of salt and KOH = 1 N

1 h. 2 h. 3 h. 5 h. 7 h. 29 h. 30 h.
Time (hours) 1 h. 2 h. 3 h. 5 h. 7 h. 29 h. 30 h.
Percent (I experiment) 2.04 3.25 4.83 7.44 9.48 30.78 —
Percent (II experiment) 2.06 3.27 4.21 6.83 — 30.33 31.46
31 h. 52 h. 77 h. 126 h. 197 h. 246 h. 431 h.
Time 31 h. 52 h. 77 h. 126 h. 197 h. 246 h. 431 h.
Percent (I experiment) 33.02 45.76 53.47 59.25 60.93 61.58 63.44
Percent (II experiment) — 45.22 53.0 58.98 61.04 61.89 62.26

8. \(\mathrm{CH_3.CH_2.CH_2.COOH}\). Concentr. 0.1 N

1 h 3 h 24 h 48 h 72 h 120 h 456 h
Time (h) 1 h 3 h 24 h 48 h 72 h 120 h 456 h
Percent (experiment I) 3.09 3.54 4.95 6.01 7.52 9.29 26.72
Percent (experiment II) 3.09 3.54 4.86 6.01 7.34 9.73 26.72
672 h 816 h 1104 h 1584 h 1896 h 2741 h
Time (h) 672 h 816 h 1104 h 1584 h 1896 h 2741 h
Percent (experiment I) 33.89 — 42.92 50.88 53.27 62.30
Percent (experiment II) 33.0 36.54 41.15 48.58 53.89 —

9. \(\mathrm{CH_3.CH_2.CH_2.COOH}\). Concentr. 0.1

15 min 30 min 1 h 2 h 3 h 96 h 192 h
Time 15 min 30 min 1 h 2 h 3 h 96 h 192 h
Percent 4.22 4.22 6.42 7.34 8.25 11.01 11.92
Time 264 h 360 h 408 h 504 h 672 h 744 h 1248 h
Percent 18.54 18.54 20.16 33.87 36.29 40.1 41.12
Time 1488 h 2808 h 3024 h 3096 h 3288 h 3408 h
Percent 44.1 61.1 61.1 63.6 63.6 65

10. \(\mathrm{(CH_3)_2CH{-}COOH}\). Concentr. 0.1 N.

2 h 3 h 48 h 72 h 120 h 456 h 675 h
Time 2 h 3 h 48 h 72 h 120 h 456 h 675 h
Percent (experiment I) 0.26 0.60 5.63 8.67 12.40 29.31 34.95
Percent (experiment II) 0.26 0.60 5.63 8.50 12.40 29.14 34.95
Time 816 h 1008 h 1200 h 1464 h 1704 h 1972 h 2596 h
Percent (experiment I) 37.55 40.58 43.62 46.74 48.04 53.42 59.41
Percent (experiment II) 37.55 40.93 43.88 46.83 47.96 53.42 59.23

11. \(\mathrm{(CH_3)_2CH.COOH}\) Concentr. 0.1

10 min 1 h 24 h 96 h 192 h 312 h 456 h
Time 10 min 1 h 24 h 96 h 192 h 312 h 456 h
Percent 1.83 4.58 4.58 10.09 15.8 29.03 35.48
Time 624 h 816 h 888 h 1512 h 1704 h 1800 h 1848 h
Percent 39.51 45.16 47.58 57.8 59.2 60.5 61.1
Time 1896 h 1992 h 2088 h 2256 h 2400 h
Percent 61.1 63.6 63.6 65 67.5

12. \(\mathrm{CH_3(CH_2)_3.COOH}\). Concentr. 0.1

3 h 24 h 49 h 72 h 120 h 144 h 192 h
Time 3 h 24 h 49 h 72 h 120 h 144 h 192 h
Percent 0.84 5.93 9.74 13.56 22.03 26.69 33.47
Time 240 h 312 h 432 h 624 h
Percent 37.71 44.06 52.45 56.27

13. \(\mathrm{(CH_3)_2CH.CH_2.COOH}\). Concentr. 0.1

3 h 24 h 48 h 144 h 216 h 336 h 408 h
Time 3 h 24 h 48 h 144 h 216 h 336 h 408 h
Percent (experiment I) 0.85 3.41 6.58 15.81 22.82 30.76 34.61
Percent (experiment II) 0.42 3.43 6.43 — 21.88 30.47 34.76
Time 528 h 672 h 840 h 984 h 1176 h 1542 h 1975 h
Percent (experiment I) 39.91 46.15 49.31 53.07 55.89 58.97 60.08
Percent (experiment II) 38.28 — 48.06 52.36 55.27 59.57 59.91
  1. $\mathrm{CH_3}\begin{matrix} \\[-1.2em] \diagdown \\[-0.4em] \diagup \end{matrix}\mathrm{CH{-}CH_2{-}COOH}$, with another $\mathrm{CH_3}$ substituent on $\mathrm{CH}$. Conc. 0.1
Time 5 min. 25 min. 40 min. 24 h. 48 h. 96 h. 144 h. 192 h. 240 h.
Percent 2.4 4.9 4.9 9.9 13.2 17.3 23.1 26.4 33.05
  1. $\mathrm{CH_3\cdot(CH_2)_4COOH}$. Conc. 0.1
Time 3 h. 24 h. 48 h. 72 h. 96 h. 120 h. 144 h. 192 h.
Percent 2.18 13.15 22.80 30.26 35.52 40.08 43.24 50.52
Time 240 h. 288 h. 336 h. 385 h. 480 h. 552 h. 648 h.
Percent 53.77 57.89 61.40 61.40 61.40 63.77 65.35
  1. $\mathrm{CH_3{-}CH_2}\begin{matrix} \\[-1.2em] \diagdown \\[-0.4em] \diagup \end{matrix}\mathrm{CH{-}COOH}$, with another $\mathrm{CH_3{-}CH_2}$ substituent on $\mathrm{CH}$. Conc. 0.1
Time 4 h. 25 h. 48 h. 72 h. 96 h. 120 h. 144 h.
Percent 0.43 4.60 8.26 11.30 14.34 17.65 20.69
Time 168 h. 216 h. 264 h. 336 h. 408 h. 480 h. 624 h.
Percent 23.47 28.26 33.82 39.65 45.65 50.60 55.30
Time 820 h. 1444 h. 2213 h.
Percent 59.47 62.34 64.78
  1. $\mathrm{CH_3(CH_2)_5\cdot COOH}$. Conc. 0.1
Time 1 h. 2½ h. 3 h. 5¾ h. 8 h. 24½ h. 29 h.
Percent 4.41 9.42 10.21 16.66 22.68 42.02 45.50
Time 50 h. 96 h. 122 h. 174 h.
Percent 56.01 62.10 63.04 63.47
  1. $\mathrm{CH_3\cdot(CH_2)_7\cdot COOH}$. Conc. 0.1
Time 1⅓ min. 5 min. 10 min. 1 h. 2 h. 21 h.
Percent 5 8.57 11.07 12.95 17.33 47.32
Time 24 h. 31 h. 48 h. 72 h.
Percent 49.73 54.73 59.82 64.28
  1. $\mathrm{CH_3(CH_2)_8\cdot COOH}$ Conc. 0.1
Time ⅔ h. 1 h. 1½ h. 3½ h. 8½ h. 19½ h. 28½ h.
Percent 4.12 5.50 8.71 16.23 24.12 52.11 56.60
Time 51 h. 74 h. 144 h. 266 h.
Percent 62.20 62.20 63.48 64.22

Oxidation in a neutral medium

  1. $\mathrm{HCOOH}$. Conc. 0.1 gram-mol/liter.
Time 0.36 min. 0.78 min. 1.16 min. 2 min. 4 min. 7 min.
Percent 25.69 33.91 37.23 38.81 39.68 40.03
  1. $\mathrm{HCOOH}$. Conc. 0.1.
Time 0.017 min. 0.033 min. 0.05 min. 0.067 min. 0.083 min. 0.166 min.
Percent 2.10 4.86 7.02 8.10 9.72 10.81
Time 0.25 min. 0.33 min. 0.417 min. 0.5 min. 0.583 min. 0.667 min.
Percent 13.51 17.83 20.54 23.24 24.32 26.48
Time 1 min. 1½ min. 2 min. 2½ min. 3 min. 3½ min. 4 min.
Percent 29.79 32.43 35.13 36.75 39.46 41.62 42.15
  1. CH₃COOH. Concentr. 0.1
Time 15 min. 30 min. 1 h. 2 h. 3 h. 24 h. 168 h. 288 h.
Percent 3.49 3.49 3.49 3.49 3.49 4.19 8.48 10.06
Time 1416 h. 1512 h. 2784 h. 3048 h. 3312 h. 3480 h. 3600 h.
Percent 10.66 11.9 12.3 12.3 12.3 17.6 17.6
  1. CH₃·CH₂·COOH. Concentr. 0.1.
Time 2 min. 10 min. 30 min. 24 h. 72 h. 120 h. 216 h.
Percent 2.86 3.57 3.57 4.29 6.43 8 11.18
Time 264 h. 360 h. 408 h. 456 h. 504 h. 552 h. 1464 h.
Percent 13.93 14.63 15.09 17.6 19.4 21.3 28
Time 1680 h. 3024 h. 3288 h. 3384 h. 3456 h.
Percent 31.4 49.1 51.5 52.8 54.08
  1. CH₃·(CH₂)₂COOH. Concentr. 0.1
Time 1 h. 3 h. 24 h. 48 h. 120 h. 456 h. 672 h.
Perc. (I experiment) 1.34 1.78 2.93 3.57 7.09 20.98 27.23
Perc. (II experiment) 1.34 1.78 3.03 4.46 7.59 21.42 27.50
Time 1008 h. 1200 h. 1440 h. 1680 h. 1896 h.
Perc. (I experiment) 35.26 38.39 41.96 47.23 50.44
Perc. (II experiment) 35.26 37.94 42.85 47.50 50.71
  1. CH₃(CH₂)₂COOH. Concentr. 0.1.
Time 2 min. 7 min. 15 min. 48 h. 96 h. 192 h. 288 h.
Percent 5.71 6.43 6.43 10.71 11.43 18.18 22.37
Time 360 h. 408 h. 600 h. 768 h. 1488 h. 1560 h.
Percent 26.66 29.09 40.61 44.84 48.7 48.7
Time 2808 h. 3096 h. 3168 h. 3360 h.
Percent 61.6 63.5 64.1 69.1
  1. (CH₃)₂·CH·COOH. Concentr. 0.1.
Time 3 h. 24 h. 48 h. 72 h. 120 h. 144 h.
Perc. (I experiment) 0.17 3.06 7.48 12.41 20.06 23.46
Perc. (II experiment) 0.17 2.97 7.47 12.30 19.77 23.17
Time 168 h. 192 h. 336 h. 408 h. 552 h. 696 h.
Perc. (I experiment) 26.44 28.14 40.73 44.98 50.93 54.33
Perc. (II experiment) — 28.94 41.34 45.67 51.18 54.49
Time 864 h. 1032 h. 1200 h. 1368 h. 2165 h.
Perc. (I experiment) 58.33 60.03 62.24 62.50 64.03
Perc. (II experiment) 58.57 — — 62.22 63.41
  1. (CH₃)₂CH·COOH. Concentr. 0.1
Time 5 min. 15 min. 1 h. 2 h. 3 h. 24 h. 48 h.
Percent 2.06 2.06 5.6 7.5 7.5 10.6 11.3
Time 120 h. 168 h. 288 h. 312 h. 360 h. 408 h. 456 h.
Percent 20.1 25.1 35.8 38.3 40 40.2 48.48
Time 624 h. 816 h. 888 h. 1152 h. 2472 h. 2664 h. 2760 h.
Percent 53.93 58.78 59.39 62.6 68.5 68.5 68.5
Time 2904 h. 3024 h. 3192 h. 3336 h.
Percent 68.5 68.5 68.5 68.5
  1. \((\mathrm{CH}_3)_2\mathrm{CH}.\mathrm{CH}_2.\mathrm{COOH}\). Concentr. 0.1.
Time 5 min. 20 min. 1 h. 2 h. 3 h. 24 h. 48 h.
Percent 3.14 3.14 3.7 4.4 4.4 11.3 18.2
Time 96 h. 144 h. 192 h. 240 h. 312 h.
Percent 24.5 32.7 37.7 43.4 48.4

Oxidation of the free acid.

  1. \(\mathrm{HCOOH}\). Concentr. 0.1.
Time 0.42 min. 0.78 min. 1.13 min. 2 min.
Percent (experiment I) 17.83 31.99 36.62 —
Percent (experiment II) 18.70 29.72 34.26 38.54
Time 4 min. 7 min. 10 min. 30 min.
Percent (experiment I) 39.68 39.68 39.68 —
Percent (experiment II) 41.43 39.68 40.55 39.68
  1. \(\mathrm{HCOOH}\). Concentr. 0.1.
Time 0.017 min. 0.033 min. 0.067 min. 0.1 min. 0.133 min. 0.166 min.
Percent 1.43 2.5 2.6 2.95 3.22 5.01
Time 0.20 min. 0.23 min. 0.25 min. 0.267 0.3 min. 0.33 min.
Percent 5.37 6.08 6.49 6.81 9.68 10.39
Time 0.417 min. 0.5 min. 0.55 min. 0.583 min. 0.667 min. 0.75 min.
Percent 11.47 14.33 18.28 20.43 22.22 25.08
Time 0.833 min. 0.916 min. 1 min. 1.5 min. 2 min. 2.5 min.
Percent 26.88 29.03 30.82 34.4 35.84 40.5
  1. \(\mathrm{CH}_3.\mathrm{CH}_2.\mathrm{COOH}\). Concentr. 0.1.
Time 15 min. 30 min. 1 h. 2 h. 3 h. 48 h. 120 h. 312 h.
Percent 0.92 0.92 1.84 3.23 3.23 3.23 3.23 4.31
Time 384 h. 1560 h. 1656 h. 2928 h. 3192 h. 3456 h. 3624 h. 3768 h.
Percent 4.31 4.5 4.5 4.5 6.2 6.25 6.25 8.3
  1. \(\mathrm{CH}_3.\mathrm{COOH}\). Concentr. 0.1.
Time 15 min. 30 min. 90 min. 24 h. 48 h. 72 h.
Percent 3.76 3.76 3.76 5.16 6.10 8.30
Time 96 h. 120 h. 192 h. 240 h. 288 h. 360 h.
Percent 9.86 9.86 16.6 19.5 19.72 22.07
Time 408 h. 456 h. 600 h. 720 h. 864 h. 1200 h.
Percent 22.07 23 24.88 32.87 40.78 [[unclear: leading digit]]6.47
Time 1320 h. 1392 h. 1464 h. 1584 h. 2328 h. 2544 h.
Percent 57.25 58.43 60.00 60.00 65.7 68.03
Time 3888 h. 4152 h. 4248 h. 4320 h. 4416 h.
Percent 70.1 70.9 70.9 70.9 70.9
  1. \(\mathrm{CH}_3.(\mathrm{CH}_2)_2\mathrm{COOH}\). Concentr. 0.1.
Time 1 h. 3 h. 24 h. 48 h. 72 h. 120 h.
Percent 0.79 1.15 4.42 8.58 12.12 18.58
Time 192 h. 240 h. 336 h. 456 h. 628 h. 672 h.
Percent 25.22 28.31 34.24 41.59 45.13 50.44
Time 816 h. 960 h. 1104 h. 1248 h.
Percent 54.86 57.78 59.20 60.35
  1. \( \mathrm{CH_3(CH_2)_2COOH} \). Concentr. 0.1.
Time 1 min 2 min 3 min 4 min 5 min 1 h
Percent 7,51 7,51 7,98 7,98 7,98 8,45
Time 2 h 3 h 24 h 48 h 168 h 192 h 216 h
Percent 8,92 8,92 8,92 12,6 24,88 25,82 28,17
Time 240 h 288 h 336 h 442 h 480 h 528 h 624 h
Percent 29,11 37,09 40,85 42,25 43,66 47,89 47,8
Time 720 h 1032 h 1560 h 2760 h 2832 h 3912 h
Percent 58,33 69,8 70,5 70,98 71,08 73,03
Time 4080 h 4200 h 4320 h
Percent 73,4 74,2 74,2
  1. \( \mathrm{(CH_3)_2.CH.COOH} \). Concentr. 0.1.
Time 0.5 h 1 h 1.5 h 2 h 3 h 4.5 h
Percent 0,25 0,42 0,84 1,26 2,10 2,94
Time 7 h 10 h 24 h 27 h 31 h 34 h 48 h
Percent 5,04 7,81 16,38 16,48 20,58 21,84 27,14
Time 58 h 72 h 120.5 h 169 h 192 h 216 h
Percent 29,83 33,27 40,58 45,12 47,98 49,24
  1. \( \mathrm{(CH_3)_2.CH.COOH} \). Concentr. 0.1.
Time 5 min 15 min 35 min 1 h 2 h 3 h 24 h
Percent 1,38 1,84 1,84 6,6 7,05 7,8 19,81
Time 48 h 72 h 120 h 144 h 192 h 288 h 360 h
Percent 29,05 30,58 40,78 45,8 51,6 54,51 57,51
Time 432 h 480 h 648 h 1032 h 1224 h 2544 h 2736 h
Percent 58,31 59,5 59,61 60,7 61,7 63,1 63,1
Time 2832 h 2976 h 3096 h 3264 h
Percent 63,9 64,1 64,3 64,5
  1. \( \mathrm{(CH_3)_2.CH.CH_2.COOH} \). Concentr. 0.1
Time 5 min 15 min 30 min 1 h 2 h 4 h 24 h 48 h
Percent 2,4 2,4 2,4 3,7 4,5 12,5 25,7 36,9
Time 72 h 96 h 144 h 192 h 240 h 288 h 406 h 504 h
Percent 54,3 54,3 63,9 64,5 65 66,39 66,8 67,6

Oxidation in the Presence of \( \mathrm{H_2SO_4} \)

  1. \( \mathrm{HCOOH} \). Concentr. 0.1.
Time 0,116 min 0,166 min 0,25 min 0,33 min 0,5 min 0,667 min
Percent 0,54 1,08 1,62 2,16 2,16 2,70
Time 1 min 2 min 3 min 5 min 10 min 15 min
Percent 3,24 3,24 4,32 4,86 9,73 11,89
Time 25 min 35 min 45 min 1 h 1.5 h 2 h
Percent 18,91 22,16 25,40 28,10 31,89 38,91
Time 3 h
Percent 40
  1. \( \mathrm{CH_3COOH} \) Concentr. 0.1.
Time 15 min 30 min 1 h 48 h 120 h 456 h 1176 h
Percent 1,41 1,41 2,11 3,52 3,52 6,06 14,7
Time 1272 h 2544 h 2808 h 3072 h 3240 h 3384 h
Percent 14,7 15,5 17,6 18,2 18,2 18,8

40. \(\mathrm{CH_3.CH_2.COOH}\). Concentr. 0.1.
Time 1 m. 5 m. 10 m. 15 m. 30 m. 1 h.
Percentages 2,86 2,86 2,86 3,57 4,29 4,29
Time 2 h. 3 h. 24 h. 48 h. 96 h. 144 h.
Percentages 5 5 5,71 5,77 6,87 10
Time 168 h. 240 h. 288 h. 384 h. 432 h. 480 h.
Percentages 18,8 21,3 28,3 28,67 34,5 38,3
Time 528 h. 624 h. 782 h. 1152 h. 2496 h. 2760 h.
Percentages 41,5 50,3 53,33 58,9 63,5 67,9
Time 2856 h. 2928 h. 3024 h. 3120 h.
Percentages 68,5 68,5 68,5 69,1

41. \(\mathrm{CH_3(CH_2)_2.COOH}\). Concentr. 0.1.
Time 3 m. 10 m. 30 m. 1,5 h. 2 h. 3 h.
Percentages 4,63 5,51 5,68 6,12 6,38 7,26
Time 5 h. 9,5 h. 22 h. 32 h. 48 h. 72 h.
Percentages 7,61 8,57 10,06 12,24 14,43 18,81
Time 100 h. 120 h. 173 h. 216 h. 264 h. 360 h.
Percentages 23,18 26,24 34,64 40,15 45,93 55,20
Time 504 h. 606 h. 1016 h.
Percentages 62,81 65,44 67,62

42. \(\mathrm{CH_3(CH_2)_2.COOH}\). Concentr. 0.1.
Time 1 m. 15 m. 25 m. 40 m. 1 h. 2 h.
Percentages 7,14 7,14 7,14 7,14 7,14 8,57
Time 3 h. 48 h. 72 h. 144 h. 192 h. 240 h.
Percentages 10 15,71 18,8 25,71 27,04 28,57
Time 288 h. 336 h. 384 h. 432 h. 480 h. 696 h.
Percentages 34,29 42,1 44,05 47,7 50,34 57,58
Time 1248 h. 2808 h. 3024 h. 3168 h. 3360 h. 3528 h.
Percentages 67,5 67,9 67,9 67,9 68,5 68,5
Time 3648 h.
Percentages 68,5

43. \((\mathrm{CH_3})_2.\mathrm{CH.COOH}\). Concentr. 0.1.
Time 0,5 h. 1 h. 1,5 h. 2 h. 3 h. 4,5 h. 8 h.
Percentages 0,41 1,25 1,92 2,09 2,92 4,18 7,53
Time 22,5 h. 27 h. 31 h. 48 h. 75 h. 99 h. 120 h.
Percentages 20,50 23,68 25,94 35,56 45,18 51,46 54,14
Time 168 h. 192 h. 241 h. 288 h. 336 h. 410 h. 482 h.
Percentages 60,25 62,00 64,35 65,94 66,77 68,28 70,04

44. \((\mathrm{CH_3})_2.\mathrm{CH.COOH}\). Concentr. 0.1.
Time 5 m. 15 m. 1 h. 2 h. 3 h. 24 h. 48 h.
Percentages 1,2 1,2 2,08 2,08 2,08 18,2 32,7
Time 72 h. 120 h. 168 h. 288 h. 360 h. 430 h. 648 h.
Percentages 38,18 49,05 57,8 61,6 63,63 64,1 64,88
Time 840 h. 2472 h. 2664 h. 2760 h. 3288 h. 3384 h. 3480 h.
Percentages 68,48 68,5 69,1 71,06 71,06 72,9 72,9
Time 3648 h. 3792 h.
Percentages 72,9 74,8
  1. \((\mathrm{CH}_3)_2.\mathrm{CH}.\mathrm{CH}_2.\mathrm{COOH}\). Concentr. 0.1.
5 min. 20 min. 45 min. 1 h. 2 h. 3 h. 24 h.
Time 5 min. 20 min. 45 min. 1 h. 2 h. 3 h. 24 h.
Percent 3,1 3,1 3,7 4,4 5,03 5,03 20,1
Time 48 h. 96 h. 144 h. 192 h. 240 h. 288 h.
Percent 32,08 48,4 57,2 62,2 65,4 65,4

Calculation of the reaction-rate constant from the results of the experiments we have followed by no means always leads to good results. Therefore, comparison of the oxidation rates of various acids and under various conditions was carried out by us, as had already been done in a whole series of earlier works, according to the intervals of time during which an equal percentage of active oxygen is expended. As the unit of comparison we took the data from the first two experiments on the oxidation of propionic acid in alkaline solution (No. 5 in the preceding tables). This acid reacts rather slowly (the most difficultly oxidized acetic acid was traced considerably worse) and under the given conditions gives a comparatively good constant for a bimolecular reaction. According to the formula:

\[ \frac{x}{a.(a-x)}\frac{1}{t}=k, \]

expressing concentrations in moles per liter, and time in seconds, we obtain:

No. of reading Duration of experiment % active oxygen expended \(k \cdot 10^{6}\)
1 24 hours = 86400 sec. 1,30 1,53
2 72 ” = 259200 ” 4,33 1,77
3 95 ” = 342000 ” 5,19 1,66
4 120 ” = 432000 ” 5,62 1,38
5 192 ” = 691200 ” 8,65 1,44
6 264 ” = 950400 ” 12,55 1,50
7 528 ” = 1900800 ” 22,51 1,53
8 672 ” = 2419200 ” 26,60 1,49
9 816 ” = 2937600 ” 31,48 1,56
10 1008 ” = 3628800 ” 34,63 1,45
11 1320 ” = 4752000 ” 38,74 1,33
12 1561 ” = 5619600 ” 41,12 1,24
13 1801 ” = 6483600 ” 46,35 1,36
14 2089 ” = 7520400 ” 49,56 1,31
15 2359 ” = 8492400 ” 51,64 1,60
16 2959 ” = 10652400 ” 54,28 1,17

Average \(k = 1{,}46 \cdot 10^{-6}\)
Average up to 40% \(k = 1{,}51 \cdot 10^{-6}\)

In the tables given below are presented the values of the average relative reaction rates for the intervals 0%–10%, 10%–20%, 20%–30%, 30%–40%, and the overall averages for 0%–40%. Obviously, in those experiments where the numbers obtained for the different intervals are close to one another, the course of the reaction is the same as for propionic acid in an alkaline medium, i.e., the oxidation proceeds according to the equation of a bimolecular reaction. A large discrepancy indicates a sharp change in the constants.

Table of relative reaction rates

Acids Series of experiments Alkaline medium 0–10 Alkaline medium 10–20 Alkaline medium 20–30 Alkaline medium 30–40 Neutral medium 0–10 Neutral medium 10–20 Neutral medium 20–30 Neutral medium 30–40 Free acid 0–10 Free acid 10–20 Free acid 20–30 Free acid 30–40 + H₂SO₄ 0–10 + H₂SO₄ 10–20 + H₂SO₄ 20–30 + H₂SO₄ 30–40
H · COOH 1 — — 0,9·10⁵ 0,6·10⁵ — — 1·10⁵ 0,8·10⁵ — — 5,7·10⁴ 5,6·10⁴ 1300 1100 850 590
H · COOH 2 5,5·10⁴ 4,4·10⁴ 3,1·10⁴ 1,8·10⁴ 1,3·10⁵ 7,5·10⁴ 6,3·10⁴ 3,3·10⁴ 2,8·10⁴ 4,3·10⁴ 5,2·10⁴ 3,6·10⁴ 0,29 0,22 — —
CH₃COOH (conc. 0.1) 2 0,043 — — — 1,1 0,12 — — 0,041 — — — — — — —
CH₃ · COOH (1 n) 1 0,041 — — — — — — — — — — — — — — —
CH₃ · CH₂COOH (0.1 N) 1 1 1 1 1 — — — — — — — — — — — —
CH₃ · CH₂COOH 2 1,54 1,03 1,17 0,84 1,83 0,98 0,62 0,53 2,35 1,84 1,24 1,37 1,85 1,96 2,20 2,34
CH₃ · CH₂COOH (1 N) 1 28,5 26,6 27,2 30,3 — — — — — — — — — — — —
CH₃ · (CH₂)₂ · COOH 1 ~4 1,33 1,34 1,41 — — — — 3,63 3,51 3,21 3,05 — 7,22 5,54 5,90
CH₃ · (CH₂)₃ · COOH 2 ~3 1,62 1,37 1,82 ~8 2,29 1,92 2,07 4,57 4,77 3,65 3,63 ~70 ~10 3,45 3,36
(CH₃)₂CH · COOH 1 3,0 1,97 1,60 1,52 3,00 3,74 3,85 4,05 14,3 15,5 14,6 12,9 19,8 20,6 21,0 22,1
(CH₃)₂CH · COOH 2 2,35 1,94 2,05 2,34 — 4,70 3,68 3,67 — 25,6 16,2 11,8 17,6 17,6 16,3 15,3
CH₃ · (CH₂)₃ · COOH 1 4,57 4,34 4,52 4,93 — — — — — — — — — — — —
(CH₃)₂CH · CH₂ · COOH 1 2,76 2,55 2,43 2,49 — — — — — — — — — — — —
(CH₃)₂CH · CH₂ · COOH 2 — 5,25 3,69 4,83 — 9,50 6,36 6,22 60 50 31 22,6 30,6 21,5 18,4 18,5
CH₃ · (CH₂)₄ · COOH 1 11,8 11,4 11,3 11,2 — — — — — — — — — — — —
(CH₃ · CH₂)₂CH · COOH 1 3,54 3,36 3,37 3,71 — — — — — — — — — — — —
CH₃ · (CH₂)₅ · COOH 1 78,4 69,7 61,3 60,0 — — — — — — — — — — — —
CH₃ · (CH₂)₇ · COOH 1 ~2·10³ 220 105 90 — — — — — — — — — — — —
CH₃ · (CH₂)₈ · COOH 1 115 95 79 88 — — — — — — — — — — — —

Mean values of the relative reaction rates
for the interval from 0% to 40%

Acids Series of experiments Medium: Alkaline Medium: Neutral Medium: Free acid Medium: +H₂SO₄
H.COOH 1 8.10⁴ 9,10⁴ 5,6.10⁴ —
H.COOH 2 4,10⁴ 8,10⁴ 4.10⁴ 1.10³
CH₃.COOH (0,1 N) 2 0,43 ∼0,6 (1,1–0,12) 0,041 0,25
CH₃.COOH (1 N) 1 0,04 — — —
CH₃.CH₂.COOH (0,1 N) 1 1 — — —
CH₃.CH₂.COOH (0,1 N) 2 1,1 0,99 1,7 2,1
CH₃.CH₂.COOH (1 N) 1 28,2 — — —
CH₃.(CH₂)₂.COOH 1 1,4 1,22 3,35 6,11
CH₃.(CH₂)₂.COOH 2 1,6 2,1 4,2 —
(CH₃)₂.CH.COOH 1 2,02 3,66 14,3 20,9
(CH₃)₂.CH.COOH 2 2,17 4,01 17,8 16,7
CH₃.(CH₂)₃.COOH 1 4,59 — — —
(CH₃)₂.CH₂.COOH 1 2,56 — — —
(CH₃)₂.CH₂.COOH 2 4,6 8,5 41,0 22,3
CH₃.(CH₂)₄.COOH 1 11,4 — — —
(C₂H₅)₂CH.COOH 1 3,5 — — —
CH₃.(CH₂)₅.COOH 1 67,2 — — —
CH₃.(CH₂)₇.COOH 1 140 — — —
CH₃.(CH₂)₈.COOH 1 94 — — —

From the tables given here the following conclusions may be drawn.

1) General course of the reaction.

For almost all the acids we studied, the course of oxidation in alkaline and strongly acidic (with H₂SO₄) media is expressed rather well by the equation for a bimolecular reaction (the very sharp drop to 40% for formic acid should not be taken into account, since 40% reduction of the permanganate corresponds to complete oxidation to carbonic acid).

The constants change more (though not for all acids) in a neutral medium and for the free acid. This should probably be explained by the very appreciable change here in the reaction medium with the accumulation of new alkali during the reduction of permanganate.

2) Effect of the medium.

Taking as unity, for each acid, the oxidation rate in neutral solution (potassium salt), we obtain the following table:

Acids Neutral Alkaline Free acid +H₂SO₄
H.COOH 1 0.84 0.69 0.19
CH₃.COOH 1 0.1 ∼0.1 ∼2
CH₃.CH₂.COOH 1 1.1 1.7 2.1
CH₃.CH₂.CH₂.COOH 1 0.76 2 ∼2
(CH₃)₂CH.COOH 1 0.53 4.4 4.2
(CH₃)₂CH.CH₂.COOH 1 0.54 4.8 2.6

We see that for all acids, except formic acid, the oxidation rate in an acidic medium is appreciably greater than in a neutral one. The addition of sulfuric acid usually has rather little effect. In formic acid, H₂SO₄ greatly slows the reaction; in acetic acid it accelerates it. The presence of free alkali almost everywhere somewhat slows the oxidation (except for acetic acid, where a large retardation was observed; however, acetic acid is difficult to compare with the others, since for it the reaction was followed far from completely).

3) Effect of chain length.

Relative oxidation rates of acids of normal structure (the oxidation rate of propionic acid under the same conditions is everywhere taken as unity).

Acids Neutral Alkaline Free acid +H₂SO₄
H.COOH 7·10⁴ 6·10⁴ 2.3·10⁴ 460
CH₃.COOH ∼0.6 0.04 0.04 0.25
CH₃.CH₂.COOH 1 1 1 1
CH₃.(CH₂)₂.COOH 1.6 1.5 2.5 ∼2
CH₃.(CH₂)₃.COOH 4.6
CH₃.(CH₂)₄.COOH 11.4
CH₃.(CH₂)₅.COOH 67
CH₃.(CH₂)₇.COOH 140
CH₃.(CH₂)₈.COOH 94

The table shows that in the homologous series of monobasic saturated acids with a straight chain the oxidation rate generally increases with increasing molecule size. Very readily oxidized formic acid is, of course, an exception, as an aldehyde acid. In addition, the results of our experiments give a certain

indication of periodicity. Acids with an odd number of links are oxidized somewhat more readily (so far observed only in an alkaline medium).

4) Influence of chain branching.

Comparison of acids with the same molecular size (e.g., isobutyric with butyric, isovaleric with valeric, diethylacetic with caproic) does not lead to a definite result, since here two influences are superimposed on one another: branching and lengthening of the chain. It turns out that, for example, \((\mathrm{CH_3.CH_2})_2\mathrm{CH.COOH}\), having a tertiary link, is oxidized more slowly than \(\mathrm{CH_3(CH_2)_4.COOH}\). The influence of branching is more clearly noticeable with the same main chain.

Propionic and isobutyric acids

Relative oxidation rate in medium: Relative oxidation rate in medium: Relative oxidation rate in medium: Relative oxidation rate in medium:
Neutral Alkaline Free acids \(+\mathrm{H_2SO_4}\)
\(\mathrm{CH_3.CH_2.COOH}\) 1 1 1 1
\((\mathrm{CH_3})_2\mathrm{CH.COOH}\) 4 2.1 10 8
per 1 H 8 4.2 20 16

Butyric, isovaleric, and diethylacetic acids:

Relative oxidation rate in medium: Relative oxidation rate in medium: Relative oxidation rate in medium: Relative oxidation rate in medium:
Neutral Alkaline Free acids \(+\mathrm{H_2SO_4}\)
\(\mathrm{CH_3.CH_2.CH_2.COOH}\) 1 1 1 1
\((\mathrm{CH_3})_2\mathrm{CH.CH_2.COOH}\) 4 2 24 10.5
\((\mathrm{CH_3.CH_2})_2\mathrm{CH.COOH}\) — 2.5 — —
per 1 H — 5 — —

Acids with a tertiary link are oxidized, under all conditions, and especially in an acidic medium, more readily. The difference becomes most noticeable if the oxidizability is calculated per one hydrogen atom, which better characterizes the strength of the carbon–hydrogen bond. The figures in this table (comparison of isovaleric acid with butyric acid), as well as the results of the qualitative test (see above on the direction of oxidation of isovaleric acid), also show that a tertiary link in the \(\beta\)-position is oxidized more readily even than the \(\mathrm{CH_2}\) group standing next to the carboxyl.

B. W. Tronow, M. T. Jalowaja and K. Ja. Budanowa.

Oxidation Rate of Monocarboxylic Acids of the Saturated Series by Potassium Permanganate under Various Conditions.

The oxidation rate of the series of saturated monocarboxylic acids from \(C_1\) to \(C_{10}\) has been determined. The acids were taken simply in aqueous solution, as salts, and in the presence of an excess of alkali and sulfuric acid. The most important conclusions are:

1) For all the acids studied by us (except formic acid), oxidation proceeds more readily in acid solution (free acid or with \(H_2SO_4\)). The addition of alkalis inhibits the reaction.

2) Formic acid is distinguished by its ease of oxidizability. For the other acids, the oxidation rate increases with the length of the chain; acids with tertiary carbon atoms oxidize more readily than those of normal structure.

  1. A series of works by J. Holluta. ↩

  2. Denis. Amer. Chem. Journ. 38, 572 (1916). ↩

  3. H. D. Dakin. Chem. Zbl. 1908. 1, 1259, 1161. ↩

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[v1] 1935

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Rate of Oxidation of Monocarboxylic Acids of the Saturated Series by Potassium Permanganate under Various Conditions