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Intermolecular versus Intramolecular Reactions

Most of the piifa values given in this text have been determined in water. How would the values of carboxylic acids, alcohols, ammonium ions (RNH3), phenol, and an anilinium ion [Pg.433]

Solution A piifa is the negative logarithm of an equilibrium constant, (Section 2.2). Because [Pg.433]

A neutral acid will be a weaker acid in a solvent that is less polar than water. [Pg.433]

Carboxylic acids, alcohols, and phenol are neutral in their acidic forms (HB) and charged in their basic forms (B ). Apolarprotic solvent will stabilize B andH more than it will stabilize HB, thereby increasing Therefore, will be larger (a stronger acid) in water than in a less polar solvent, so the values of carboxylic acids, alcohols, and phenol will be smaller (they will be weaker acids) and, therefore, their values will be larger in a less polar solvent. [Pg.433]


Doubly labeled compounds provide an interesting test for an intermolecular versus intramolecular transfer of a group. The group transferred and another part of the same molecule are both labeled, and the reaction is run with an equal amount of unlabeled material. The product of an intramolecular transfer would be either doubly labeled or unlabeled. The intermolecular process would produce a statistical mixture of products About half the product would be singly labeled. [Pg.315]

Additional experimental, theoretical, and computational work is needed to acquire a complete understanding of the microscopic dynamics of gas-phase SN2 nucleophilic substitution reactions. Experimental measurements of the SN2 reaction rate versus excitation of specific vibrational modes of RY (equation 1) are needed, as are experimental studies of the dissociation and isomerization rates of the X--RY complex versus specific excitations of the complex s intermolecular and intramolecular modes. Experimental studies that probe the molecular dynamics of the [X-. r - Y]- central barrier region would also be extremely useful. [Pg.154]

When there is the intention of effecting an allylic rearrangement in the C—C bond formation step, it is obvious that intramolecular processes are principally better than intermolecular ones as there always exists the competition of 5n versus Ss reactions with intermolecular processes, although there have been a number of improvements regarding this problem in recent years. Because of the huge amount of literature only selected examples, which demonstrate the general trends, can be presented here. [Pg.847]

Pressure effects on the diastereoselectivity can also be observed for intramolecular cycloadditions such as the hetero-Diels-Alder reaction of 90, even though the AAV are smaller compared to intermolecular reactions (Scheme 8.23). The kinetics were again measured by on-line FT-IR spectroscopy and the stereoselectivity by HPLC. At atmospheric pressure in toluene under reflux the reaction of 90 led to a 5.2 1 ratio of the diastereomeric cycloadducts 91 and 92 in 93 % yield. Increasing pressure favors the formation of the cis-adduct 91, which is probably formed via an endo-E-syn transition structure. Interestingly, in the ground state of 90 the Z-configuration is more stable and it is therefore assumed that isomerization of the Z- to the B-double bond occurs prior to the cycloaddition [51]. From the slope of the plot of ln(91/92) versus pressure, AAV is calculated to be -(1.6 + 0.2) cm mol with the individual values for AV = -(19.4 + 0.2) and AV = —(17.9 0.6) cm mol at 343 K. Although the AV values are relatively low in comparison with data reported for other intramolecular Diels-Alder reactions e.g. [Pg.261]

Figure 5. Effective values of rates for intermolecular (K4) and intramolecular (K5) secondary amine reaction versus cure time for TGDDM/DDS. Figure 5. Effective values of rates for intermolecular (K4) and intramolecular (K5) secondary amine reaction versus cure time for TGDDM/DDS.
The intermolecular isotope effect in reactions 110 and 111 for 2.8eV tritium atoms generated by photolysis of TBr at 1849 A, as measured by the ratio [(CH3T/CH4)/(CD3T/CD4)], has been found to equal 7.2. The ratio for the intramolecular competition for the T for H versus T for D substitution in partially deuteriated methanes (equations 112 and 113) is approximately unity, as measured semi-quantitatively by the ratio of product yields, [CHD2T]/[CH2DT] = 1.06 + 0.1. [Pg.843]

Catalytic centers can be easily isolated in the intracrystalline space of zeolites. As discussed above, the Br0nsted acid sites are isolated from a certain concentration, viz. critical Si/Al ratio, onwards. As a result it is possible to promote/suppress intramolecular versus intermolecular reactions depending on the overall chemical composition of the intracrystalline zeolite space [90]. Also, occluded metal complexes can be isolated and give rise to new catalytic chemistry [91, 92]. [Pg.254]


See other pages where Intermolecular versus Intramolecular Reactions is mentioned: [Pg.279]    [Pg.428]    [Pg.433]    [Pg.435]    [Pg.279]    [Pg.428]    [Pg.433]    [Pg.435]    [Pg.304]    [Pg.39]    [Pg.180]    [Pg.7]    [Pg.830]    [Pg.287]    [Pg.2]    [Pg.150]    [Pg.830]    [Pg.121]    [Pg.240]    [Pg.524]    [Pg.181]    [Pg.210]    [Pg.603]    [Pg.10]    [Pg.4087]    [Pg.4087]    [Pg.53]    [Pg.553]    [Pg.108]    [Pg.321]    [Pg.553]    [Pg.530]    [Pg.285]    [Pg.53]    [Pg.4086]    [Pg.4086]    [Pg.285]    [Pg.307]    [Pg.552]    [Pg.558]    [Pg.84]   


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