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dc.contributor.authorCoutie, Alexanderen
dc.date.accessioned2018-05-22T12:50:51Z
dc.date.available2018-05-22T12:50:51Z
dc.date.issued1925en
dc.identifier.urihttp://hdl.handle.net/1842/30973
dc.description.abstractThe most definite information as to the mechanism of their action has been given by the weak organic bases. As far as concerns that stage of the reaction to which the velocity constants observed refer, tertiary organic bases react with formaldehyde in virtue of their hydroxyl ion concentration, and one molecule of base reacts with one of aldehyde. There may be other stages in the change, but they must be infinitely fast compared with the one measured. This would suggest that the reaction takes a course such as,en
dc.description.abstractHCHC + OH' = H000' + 2H (slow) HMO - 2H = CH3 tH (Fast)en
dc.description.abstractThere is a considerable amount of evidence in favour of such a course, (cf.page 31) .en
dc.description.abstractEvidence as to the mechanism of the reaction is by no means so clear when the strong inorganic bases are considered. That it is essentially the same with the alkalies and the alkaline earths is proved by conductivity and other measurements, (pages 83 -87). The increasing irregularity in the monomolecular constants with increase in the ratio of base to alde- -hyda, especially noticeable for barium and strontium hydroxides, suggests that the concentration of form- -aldehyde is becoming insufficiently great to keep the reaction apparently monomolecular, and indicates that the strong inorganic bases play a direct part in the change, and are not removed in some secondary way. The velocity constants for these bases rise both with increasing concentration of aldehyde and of base. The rate of increase in the first case, is not proportional to any integral power of the formaldehyde concentration,- even when allowance is made for various disturbing factors, such as active forms of the aldehyde and base.en
dc.description.abstractSeveral attempts have been made to explain the increase in constants with increasing concentration of base. Naturally, the first suggestion is that the act- - -ivity of the base is due to its concentration of un- -ionised molecules, and this is favoured, in a general way, by the effect of neutral salts on the velocity of the reaction.en
dc.description.abstractThe proposal that the unionised molecules of all the strong inorganic bases have the same specific effect in promoting the reaction studied, and that an increase in the concentration of these is alone responsible for a rise in the velocity constants is disproved by the behaviour of strontium and calcium hydroxides.en
dc.description.abstractNeutral salt action of the unionised formaldehyde salt present might be given as an explanation of the increase in constants with rising concentration of each individual strong inorganic base, and also of the variation in these in passing from one such base to another. There is a certain amount of evidence in favour (page 91) , but the proposal is considered to be, in itself, insufficient.en
dc.description.abstractThe study of the velocity constants obtained with these inorganic bases, leads to the conclusion that some derivative of the base exerts a catalytic effect, characteristic of the base, and increasing in magnitude from sodium, through barium and strontium, to calcium. üxperiments with trimethylamine, (pages 98 101), give strong, and quite independent , support to this conclusion. It is possible, from results obtained with this weak organic base to give a relative value to the cataly tic effect exerted by the derivatives of the strong inorganic bases. On subtracting the approp- -riate catalytic figure from the constants given by the strong inorganic bases, values are obtained which are practically identical for all these bases - at corresponding concentrations of base and aldehyde. This leads to the conclusion,- already reached on othekr grounds, (pages 83 -87) , -that the mechanism of react ion of the various strong inorganic bases is essentially the same .en
dc.description.abstractIt is difficult to settle what derivative of the inorganic base is responsible for the catalytic effect.. As has been proved on page 101, it is certainly not hydroxyl ions. A consideration of the various possible:, catalysts shows that the most probable are the metallic ions,and the unionised molecules of free inorganic base.en
dc.description.abstractOwing to difficulty in the determination of the hydrolysis constant of a diacid base, it is impossible to give an equation representing the behaviour of the alkaline earths in their action on formaldehyde, but a formula can 'be suggested for the alkalies, to rep- -resent roughly the state of affairs found in practice. If it be supposed that the reaction is primarily due to hydroxyl ions, and that the catalytic effect is caused by unionised molecules of the free inorganic base, and thE.t the effect is proportional to the con- -centration of these molecules, then, Rate = (41+ B) [Total Base] whe re , whe re B .t . h. i: . [.r.!: V l ll] Y ïlLi 01-1 01 + h tL.h. (1-m) [jr0i10] + h k = fundamental velocity constant of reaction. K = catalytic effect of unionised. molecules of base. The observed velocity constants would be the sum of these two, is. h alt; f h m. (k. Ellefig] - Al + gJ If the concentration of base be increased, - that of foraldehyde remaining constant,- m will decrease slightly, and, if it be assumed that Y. is greater than k. [HMO] y, then a smaller and smaller quantity has to be subtracted from and, therefore the constant increases. This expression would also give a gualitative explanation of the effect of increasing the con - -contrat ion of formaldehyde, while keeping that of the base fixed. This equation, k.h.Tn. [ -ECHO] Y Iasi (l -m) Rate = + [Total Base [ UH:A + h [I. CH O] + n also expresses the results obtained with the weak organic bases, as the catalytic effect ,K , is equal to zero, and the first term simplifies to (lae LICI10] y) since the formaldehyde salt is practically completely hydrolysed. 1e. fate = {k.m. [IICHOYJ [Total Base] ( cf. page 95) .en
dc.description.abstractWhile this equation is merely a suggestion, it serves to show that there is no reason why the mechanism of the reaction between the strong inorganic baUeS and formaldehyde .should not be fundamentally N identical with that. of the weak organic bases. It must be admitted that the inorganic bases have given very little definite information on which to found an argu -- -ment, but, taking everything into consideration, it would seem that both react with formaldehyde in virtue of their hydroxyl ion concentration, but that, in addijtio4 the strong inorganic bases possess a catalytic power characteristic of each individual base.en
dc.description.abstract# # # # # # # # # # #en
dc.description.abstractPolymolecular chemical reactions are of two types. The first class consiste of these in which one molecule of each of n different substances, all originally present in the same concentrations, is necessary and sufficient for the occurrence of the change. The differential equation assumes the formdC /dt = k.C.C.C.0 (n times) = k.Cn (1) (All concentrat ions in this section may be taken as measured in gram molecules per litre.) The other class is much more general, and ineludes those reactions in which the n molecules, actually taking part in the change, are not all d if- -ferent . If m molecules of substance A, reacting with initial concentration CI, disaPpear for every mzl molecules of substance P,- of original concentration ?..27, used up, and so on whe re 1C/dt. = k.C,,C,C, ....CCLCa...,C3C3 ... = k. Cr¡' Cla C3'3 (2) = n. This equation can be tut in a more useful form. if several substances :,?,C, ...with initial con- -Centrations á.,ú,c, .. .take tart in a simple reaction, Una-isturbed b any simultaneous or secondary changes, and if 1,L.,n, ...are the number of molecules of .A,B,C, . which must react simultaneously before the change considered can take place, then, where x would be the actual fall in concentration in time t, of a substance of which only one molecule was necessary for the progress of the reaction, dx/dt = k(a lx) 1 (b mx) m (c nx) n (3) the number of factors being equal to the number of different substances taking part in the reaction. If any substances which do not react, are present, the corresponding factor has the exponent zero, and is thus unity/ e.g. (c - Ox)U == o0 == 1. i similar 1) eqiiation has been given by "Iegscheider, in a paper on "The most general form of chemico-kinetic equations for homogeneous systems':en
dc.publisherThe University of Edinburghen
dc.relation.isreferencedbyen
dc.subjectAnnexe Thesis Digitisation Project 2018 Block 19en
dc.titleThe action of bases on formaldehyde: Part 1. The formation of salts of formic acid from formaldehyde; and polymolecular chemical reactionsen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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