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This is a general revision of the kinetics of iodine addition, w i t h a note on the equilibria in The rate of iodine addition over the concentration range that can be measured these reactions. is given by the expression the first term being chiefly operative in solvents such a s chlorobenzene, carbon tetrachloride, and carbon disulphide, and the second term in isobutyl ether, acetic acid, and nitrobenzene solutions. With certain aromatic compounds such as styrene and its derivatives iodine addition is accompanied by polymensation.AN earlier investigation on the kinetics of iodine addition (Bythell and Robertson, I., 1938, 173) established that these reactions, like the corresponding bromine and iodine chloride additions, showed third-order kinetics, with a small temperature coefficient in acetic acid and nitrobenzene solutions. Erroneous theoretical conclusions, however, were made from the measurements in carbon tetrachloride solution, chiefly as a result of confining the observations to a single compound, ally1 alcohol, the behaviour of which is now found to be anomalous. In the meantime several communications on the kinetics of iodine addition have appeared. Bhattacharyya and Rao ( J . Indian Chem. Soc., 1941, 18, 253), using 2-pentene and phenylacetylene as reactants, found third-order kinetics for iodine addition in acetic acid and ethyl alcohol solutions. Ghosh et al. (ibid., p. 245) state that iodine addition in carbon tetrachloride, carbon disulphide, and benzene solutions proceeds by a fourth-order mechanism. These observers, following Groh and Szelestey (2. anmg. Chem., 1927, 162, 333), who had previously investigated erucic acid in carbon tetrachloride and carbon disulphide and found f ourth-order kinetics, employed an elaborate formula, derived from the integration of the expression, -d[IJ/dt = k,[A][IJ3 -h,[AII][I2]2, and obtaining constant K, coefficients for p-amylene and pinene, concluded that the reaction proceeds, A + I,We, on the other hand, have followed the simpler procedure of adjusting the concentrations with one reactant A in excess, to reduce the effect of the reverse reaction, and have evaluated the reaction order by measurements a t different initial concentrations. To obtain the relative contributions of A and I, to the total reaction order, use was made of the formula : A11 +-21,. t,/t, = (c,/c,)"-* (G'"")":where t , and t, are the times of an equal fractional change of iodine addition, with concentrations cI and c2 for I,, and c' and c" for A, n being the order for I, and n' for A. The proposed formula holds only for the initial stages of the reaction, to -10% iodine addition, over which range, as is found experimentally, the yo addition-time curves are approximately straight lines.Employing this formula, we have established that in polar solvents, e.g., acetic acid, isobutyl ether, chloroform, chlorobenzene, and nitrobenzene, the reaction order for the organic compound (A) is unity ; in the non-polar solvents carbon tetrachloride and carbon disulphide, on the other hand, the v...

Summary A slow‐greening mutant growing at a slower rate than control plants is described. Mutant plants produce less chlorophyll than control plants, and their rate of production of pigment is lower. There is some evidence that chlorophyll is broken down in the mutant under high light conditions. Plastid numbers per leaf cell are similar in control and mutant, but a reduction in leaf cell number in the mutant results in their containing fewer plastids per leaf. The slow accumulation of chlorophyll by plastids of the mutant is correlated with a slow development of plastid fine structure, in particular in stacking of grana, as seen by electron microscopy.

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Direct fluorination of hexachlorobenzene gives chlorofluorocyclohexanes of average composition [C,Cl,F,] . Dehalogenation of this mixture with iron filings packed in a cobalt fluoride reactor gives high yields of hexafluorobenzene and chlorofluorobenzenes. Chloropentafluorobenzene forms a Grignard reagent with magnesium in diethyl ether when activated with 1,2-dibromoethane but forms material of high molecular weight when tetrahydrofuran is used as solvent.