I. I. Molodykh.

On the Mobility of Halogens in Polyhalogenated Organic Compounds.

Laboratory of Organic Chemistry.

To verify the theoretical propositions set forth in B. V. Tronov’s article “The Mobility of Halogens in Organic Compounds as a Function of the Electrochemical Character of the Radical with Which the Halogens Are Bound,” I carried out observations on the rate of elimination of halogens in a series of compounds: $\mathrm{CH_2Cl_2}$, $\mathrm{CHCl_3}$, $\mathrm{CCl_4}$, $\mathrm{CH_2Br_2}$, $\mathrm{CHBr_3}$, $\mathrm{CH_2Cl.CH_2Cl}$, $\mathrm{CH_2Cl.CH_2Br}$, $\mathrm{CH_2Br.CH_2Br}$, $\mathrm{CH_3.CHBr.CH_2Br}$, $\mathrm{CH_2Br.CH_2.CH_2Cl}$, $\mathrm{CH_2Br.CH_2.CH_2Br}$.

Works of a similar kind (Hecht, Conrad, Brückener, J. Wislicenus, and others) encountered in the literature relate chiefly to compounds containing one halogen atom in their composition.

For the experiments, substances from the firm Kahlbaum were used, thoroughly dried and freshly redistilled.

Measurements of the reaction rate were carried out: with caustic potash in ethyl alcohol*); with sodium isobutylate in isobutyl alcohol; with silver nitrate in ethyl alcohol; and with sodium iodide in acetone and isobutyl alcohol, the reacting components being taken in equivalent amounts, on the assumption that one halogen atom is eliminated.

The titer of the caustic potash and of the sodium isobutylate was established by hydrochloric acid; the silver nitrate and sodium iodide were accurately weighed and dissolved in a definite amount of solvent.

In the interaction of the halogen derivative with each of the above-mentioned reagents, a precipitate of $\mathrm{KX}$, $\mathrm{NaX}$, or $\mathrm{AgX}$ was obtained, where $\mathrm{X}$ is $\mathrm{Cl'}$ or $\mathrm{Br'}$.

The precipitated solid was separated and titrated with a solution of silver nitrate by Volhard’s method, with a correction being made for solubility. This method of work was employed in order to obtain uniform results.

In experiments with silver nitrate, the amount of halogenated silver formed was determined by weight.

All experiments were conducted at room temperature, $16^\circ \mathrm{C}$.

The constants were calculated according to the formula:

\[ AK = \frac{x}{A - x} \cdot \frac{1}{t}, \]

where $x$ denotes the amount of halogen salt of Na, K, or Ag formed during time $t$; $t$ is the time in minutes, and $A$ is the amount of salt that can be formed if the reaction goes to completion.

*) Alcohol of local manufacture.

The results of the observations were expressed by the following tables:

Experiments with caustic potash.

Table 1.

\(\mathrm{CH_2Cl_2 + KOH.}\)  \(A = 0,2230.\)

Hence \(K = 0,00002066.\)

Table 2.

\(\mathrm{CHCl_3 + KOH.}\)  \(A = 0,2230.\)

Hence \(K = 0,001047.\)

Table 3.

\(\mathrm{CCl_4 + KOH.}\)  \(A = 0,2230.\)

Hence \(K = 0,0000418.\)

Table 4.

\(\mathrm{CH_2Br_2 + KOH.}\)  \(A = 0,3561\)

Hence \(K = 0,00004024.\)

Table 5.

\(\mathrm{CHBr_3 + KOH.}\)  \(A = 0,3561.\)

Hence \(K = 0,02590.\)

Table 6.

\(\mathrm{C_2H_4Cl_2 + KOH.}\)  \(A = 0,2636.\)

Hence \(K = 0,0002079.\)

Table 7.

\(\mathrm{C_2H_5Br + KOH.}\)  \(A = 0,3561.\)

Hence \(K = 0,00241.\)

Table 8.

\(\mathrm{C_2H_4ClBr + KOH.}\)  \(A = 0,4210.\)

Hence \(K = 0,00707.\)

Table 9.

\(\mathrm{C_2H_4Br_2 + KOH.}\)  \(A = 0,4210.\)

Hence \(K = 0,0308.\)

Table 10.

\(\mathrm{CH_3.CHBr.CH_2Br + KOH.}\) \(A = 0,4143.\)

Hence \(K = 0,0140.\)

Table 11.

\(\mathrm{CH_2Cl.CH_2.CH_2Br + KOH.}\)
\(A = 0,4143.\)

Hence \(K = 0,00140.\)

Table 12.

\(\mathrm{CH_2Br.CH_2.CH_2Br + KOH.}\)
\(A = 0,4143.\)

Hence \(K = 0,00796.\)

Experiments with sodium isobutylate.

Table 13.

\(\mathrm{CH_2Cl_2 + iC_4H_9ONa.}\)  \(A = 0.1749.\)

Hence \(K = 0.0000317.\)

Table 14.

\(\mathrm{CHCl_3 + iC_4H_9ONa.}\)  \(A = 0.1749.\)

Hence \(K = 0.00195.\)

Table 15.

\(\mathrm{CCl_4 + iC_4H_9ONa.}\)  \(A = 0.1749.\)

Hence \(K = 0.0000941.\)

Table 16.

\(\mathrm{CH_2Br_2 + iC_4H_9ONa.}\)  \(A = 0.3079.\)

Hence \(K = 0.0000258.\)

Table 17.

\(\mathrm{CHBr_3 + iC_4H_9ONa.}\)  \(A = 0.3079.\)

Hence \(K = 0.0122.\)

Table 18.

\(\mathrm{C_2H_4Cl_2 + iC_4H_9ONa.}\)  \(A = 0.2067.\)

Hence \(K = 0.000565.\)

Table 19.

\(\mathrm{C_2H_5Br + iC_4H_9ONa.}\)  \(A = 0.3079.\)

Hence \(K = 0.00146.\)

Table 20

\(\mathrm{C_2H_4ClBr + iC_4H_9ONa.}\)  \(A = 0.3641.\)

Hence \(K = 0.00787.\)

Table 21.

\(\mathrm{C_2H_4Br_2 + iC_4H_9ONa.}\)

\(A = 0.3641.\)

Hence \(K = 0.0309.\)

Table 22.

\(\mathrm{CH_3.CHBr.CH_2Br + iC_4H_9ONa.}\)

\(A = 0.3583.\)

Hence \(K = 0.0150.\)

Table 23.

\(\mathrm{CH_2Cl.CH_2.CH_2Br + iC_4H_9ONa.}\)

\(A = 0.3583.\)

Hence \(K = 0.00162.\)

Table 24.

\(\mathrm{CH_2Br.CH_2.CH_2Br + iC_4H_9ONa.}\)

\(A = 0.3583.\)

Hence \(K = 0.00920.\)

Experiments with sodium iodide in acetone.

Table 25.

\(\mathrm{CH_2Cl.CH_2Cl + NaJ.}\) \(\quad A = 0.1654.\)

Hence \(K = 0.0000738.\)

Table 26.

\(\mathrm{CH_2Cl.CH_2Br + NaJ.}\) \(\quad A = 0.2912,\)

Hence \(K = 0.008915.\)

Table 27.

\(\mathrm{CH_2Br.CH_2Br + NaJ.}\) \(\quad A = 0.2912.\)

Hence \(K = 0.0202.\)

Table 28.

\(\mathrm{CH_3.CHBr.CH_2Br + NaJ.}\)

\(A = 0.2912.\)

Hence \(K = 0.000540.\)

Table 29.

\(\mathrm{CH_2Cl.CH_2.CH_2Br + NaJ.}\)

\(A = 2912.\)

Hence \(K = 0.106.\)

Table 30.

\(\mathrm{CH_2Br.CH_2.CH_2Br + NaJ.}\)

\(A = 0.2912.\)

Hence \(K = 0.179.\)

Experiments with sodium iodide in isobutyl alcohol.

Table 31.

\(\mathrm{CH_2Cl.CH_2Br + NaJ.}\) \(\quad A = 2927.\)

Hence \(K = 0.0000725.\)

Table 32.

\(\mathrm{CH_2Br.CH_2Br + NaJ.}\) \(\quad A = 2927.\)

Hence \(K = 0.000162.\)

Table 33.

\(\mathrm{CH_3.CHBr.CH_2Br + NaJ.}\) \(A = 0.2927.\)

Hence \(K = 0.00000464.\)

Table 34.

\(\mathrm{CH_2Cl.CH_2.CH_2Br + NaJ.}\) \(A = 0.2927.\)

Hence \(K = 0.000862.\)

Table 35.

\(\mathrm{CH_2Br.CH_2.CH_2Br + NaJ.}\) \(A = 0.2927.\)

Hence \(K = 0.003935.\)

In the experiments with sodium iodide, a considerable difficulty was presented by the circumstance that, in all cases where two halide atoms stood at adjacent units, \(J_2\) was liberated.

Experiments with silver nitrate.

Table 36.

\[ \mathrm{CH_2Cl.CH_2Br + AgNO_3.}\qquad A=0.5527. \]

Hence \(K=0.00002055\).

Table 37

\[ \mathrm{CH_2Br.CH_2Br + AgNO_3.}\qquad A=0.3309. \]

Hence \(K=0.000192\).

Table 38.

\[ \mathrm{CH_3.CHBr.CH_2Br + AgNO_3.} \]
\[ A=0.3309. \]

Hence \(K=0.000692\).

Table 39.

\[ \mathrm{CH_2Cl.CH_2.CH_2Br + AgNO_3.} \]
\[ A=0.3309. \]

Hence \(K=0.000782\).

Table 40.

\[ \mathrm{CH_2Br.CH_2.CH_2Br + AgNO_3.}\qquad A=0.3309. \]

Hence \(K=0.00248\).

Summary table of constants.

If, for comparison of the constants of the halogen compounds studied, we take the smallest of them as unity, the following is obtained:

1.

Relative magnitude of the constants in experiments with NaJ in acetone.

2.

Relative magnitude of the constants in experiments with NaJ in isobutyl alcohol.

3.

Relative magnitude of the constants in experiments with KOH.

4.

Relative magnitude of the constants in experiments with iC₄H₉ONa.

5.

Relative magnitude of the constants in experiments with AgON₃.

Conclusions.

1. Accumulation of halide atoms accelerates the reaction with caustic alkali and alcoholates. An exception is CHCl₃ (and, probably, CHBr₃), which reacts faster than CCl₄. This can be explained by the presence, at the carbon atom, of a very mobile hydrogen.

2. Lengthening of the chain decreases the mobility of the halide.

3. Comparison of the studied halogen derivatives of ethane and propane shows that the closer the halide atoms are to one another, the more readily they react with KOH and iC₄H₉ONa, and the more difficult the reaction with NaJ and AgNO₃ proceeds.

4. The nature of the solvent strongly affects the rate of the reactions investigated; thus, in reactions with NaJ in acetone, the constant proves to be approximately 120 times greater than for the same reaction in isobutyl alcohol.

5. Since bromine in organic compounds is always more mobile than chlorine, when both of these halides are present in the molecule, bromine reacts first.

Literature:

1. Tronov B. V. Zh.R.F.Kh.O., vol. 58, 1276 and vol. 61, 345.
2. Timofeev. Zh.R.F.Kh.O., vol. 15, 377.
3. Gustavson. Zh.R.F.Kh.O., vol. 23, 253.
4. Bryussov. Zh.R.F.Kh.O., vol. 32, 7.
5. Kruger E. V. Zh.O.Kh., vol. 3, issue 1, 67.
6. Petrenko-Kritchenko. Zts f. phys. Ch. 116, 313.
7. Wilderman. Zts f. phys. Ch. 8, 661.
8. Euler. Zts. f. phys. Ch. 100, 171.