The absorption spectrum of hydrogen peroxide was re-examined with a prism instrument in the region 1.5 to 25p. A pair of well-resolved perpe~iclicular bands arising from torsional oscillation of the OH groups \\?ere found centered about 460 and 575 cm.?. The overtone band a t 3 . 8 ,~ was shown to be a hybrid with prominent rotational str~rcture and some indicatio~is of doubling. Its assignnlent to the combination v?+vs implies a positive anharrnonicity. Four new overtone bands were observed in liquid hydrogen peroxide. The infrared spectrum of d c u t e r i~~l n peroxide was ~neasured for the first time in the solid and vapor states. Previous investigations of the ~nolecular spectrum of hydrogen peroxide (2, 6, 10, 30, 34) have served to confirm the structure now accepted for that molecule but, otherwise, they have left unanswered a number of important questions, such as the assignment of the weak band a t 3.SP and the frequency of the four symmetric modes, especially v r the torsional oscillation. In an eiiort to solve some of these problems the infrared spectrum of that compound was measured again under a wider range of conditions than covered heretofore. In addition, the completely cleuterated peroxide was prepared and its spectrum in the vapor state was recorded for the first time. RiIixtures of these two isotopic peroxides mere used to obtain valuable information on the hybricl molecule HDO?. Unlortunately, study of the latter was severely limited by interference from the parent molecules HzOz and D z 0 2 , always present in large proportions, in addition to traces of HzO, DzO, and HDO. Finally the spectra of the three peroxides dissolved in a non-polar solvent have helped elucidate the region of the 0-H and 0-D stretching fundamentals. While the subject remains far from exhausted the new results have made possible calculation of the force constants of the molecule (11) and an appreciable refinement in our knowledge of the structural parameters.

No abstract

A stutly has bee11 111ntle of the variation of the r e a c~i o~~ rate con-iLa~lt ill^ increasing dilution ill the case of three reactions bet\\.een pairs oi tlil,olnr substallces i r~ cthanol a o l u t i o~~. The reactions esnrninccl were chow I1ci\vec11 aniline ant1 2,i-tlinitrochlorot1e11zcnc, p-toluitline and 2,i-clini~rochlorol~c11ze11e. ancl p-tol~~icline and 2,-L-~linitrobron1oben2e11e. As the conce~iLratic.rr~> oi ~l i c reactants in the l i r s~ t\\-o cases are increased 50-fold, the I,i~nolcc~~lnr \-elocity cocficient clec~waacs Irl-npproxirnately L2YD in the case oi the lirjt reaction, artd by 7% in the case of the sccontl one. T h e rates decrease shnrpl>. a; the ;olubility limits of the protl~~ccs i r~ ethanol are appronchctl, while the!. I1cco111c relatively const;~nt as high tlill~tions are attained. IntroductionIn kinetics, the name given to the variation in the constants of the .~r r t~e n i i i s equation, viz. k , A , and E as a function of a change in initial concentration of the reactants, is the 'dilution effect'. T h e dilutio~i effect llas bee11 experimentally studied and 1heo1-ies lla\-e been developed for ion-ion, ion-clipole, enz).nle, and chain reactions, a s well a s lor ~~nimolecular decompositions ( 8 ) . Apart fronl their possible signiticance in tlie interpretatiorl of reaction mechanism a n d solvent effects, these dilution effects are of i n k r e s t b e c a~~s e the!-may have t o be taken into account in the cornparison of the rates of a reaction in different solvents. W e are here concerned with the dilution eftect in the case ot reactions between two dipolar substances.T h e bimolecular velocitj-coefficient of reactions betn-eel1 alkl-l I~alicles and ions in hydroxplic solvents increases a s the dilution is incl-eased, often tenclingt o a l i m i t i~~g value a t high clilutions which is from t\vo to four times a s great a s the value found a t a concerltration of one gram rnole per litel-. T l i~~s I-Iecht and Conracl (6) found t h a t tlie rate of the reaction bet\\-ecn methyl ioclicle and s o d i~~n i ethoxide in ethanol solution at 3G°C. nras cloublecl when llie dilution was increased from 2 t o 100 liters per mole. Acree and Iiobertson (1) interpretecl these phenomena in terms of the dual hypothesis and derived a relation of the typewhere k i and k , are the react~vities of the ion and of the ~~nclissociatecl molecule, and a is the degree of ionization. Later workers, e.g. RIitchell (7) found t h a t k,,, was negligible in man). reactions of this t j p e , and thus concl~tded t h a t the bimolecular velocity coefficient calculated on the basis of the corlcelltration of the reactive ion rather than on the total concentration of base was independent of dilution. 1 ~Lfan~cscript receited ,in oririnal for~rr ilzigust 14, 1.9.50, and, as revised. rlpril 16, 1951. Co?ztribution from the