Substituted Ethylenes

It is essential to apply both tests, since some symmetrically substituted ethylenic compounds (e.g., ilbene C4H5CH=CHCjHj) react slowly under tbe conditions of the bromine test. With dilute permanganate solution the double bond is readily attacked, probably through the intermediate formation of a cis diol ... 

Formation of ketones by brominatlon rearrangement ot substituted ethylenes. 

The chemical reactivity of these two substituted ethylenes is in agreement with the ideas encompassed by both the MO and resonance descriptions. Enamines, as amino-substituted alkenes are called, are vety reactive toward electrophilic species, and it is the p carbon that is the site of attack. For example, enamines are protonated on the carbon. Acrolein is an electrophilic alkene, as predicted, and the nucleophile attacks the P carbon. 

Substituent constants calculated in this way are in good agreement with empirical Of values. The same system was used to calculate values by determining charge accumulation or depletion on the a and p carbons of substituted ethylenes using the 4-3IG method. 

PVC, the polymerization product of chlorine-substituted ethylene derivatives, is probably the most widely used plastic for process plant construction. It is available in four different types rigid, high impact, high temperature and plasticized. 

Certain physical properties of substituted ethylenes may be correlated with the extended Hammett equation. Included in this category are dipole moments and ionization potentials. 

Sharp and Walker (36) have reported good linear plots of Mx - Mh for 3- and 4-substituted pyridines, pyridine-N-oxides and nitrobenzenes against the appropriate substituent constants. Charton (37) has reported correlations of dipole moments for substituted ethylenes and related compounds with eq. (1) using the oj, and Op constants. Best results were generally obtained with Op. 

A number of correlations of ionization potentials for substituted benzenes (40-42), benzyl (43), phenoxy (44), and alkyl (45) radicals and substituted pyridines (46) with the simple Hammett equation have been reported. Charton (47) has studied the application of the extended Hammett equation to substituted ethylenes and carbonyl compounds. The sets studied here are reported in Table II (sets 2-10 and 2-11). Results of the correlations are set forth in Table 111. The results obtained are much improved by the exclusion of the values for X = C2 H3, Ac, F, H and OAc from set 2-10 (set 2-lOA) and the value for X = H from set 2-11 (set 2-11 A). The composition of the electrical effect corresponds to that found for the Op constants as is shown by the pR values reported in Table IV. 

The only physical property which has been studied for substituted vinylidene sets is the nmr chemical shift of the vinylidene proton in substituted ethylenes and in tra s-l,2-disubstituted ethylenes. The first attempt at correlating chemical shift data for substituted ethylenes with the Hammett equation appears to be the work of Banwell and Sheppard (53), who reported a correlation of A2 values with the or constants, the A2 values being defined by the equation... 

Chemical shifts of cis protons in substituted ethylenes and in trans-1,2-disubstituted ethylenes have been correlated with the Hammett equation in... 

We have also examined the effect of substituents on orientation in the addition of BH3 to the carbon-carbon double bond. Consider the substituted ethylene XCH=CH2. The boron may become bonded either to carbon 1 or to carbon 2. The overall rate constant for the reaction is given by... 

Kawabata, Tsuruta, and Furukawa (121) have reported a linear relationship between the logarithms of their Q values and the logarithms of the methyl affinities of Szwarc and co-workers (111, 123, 124). James and MacCallum (125) have found a linear relationship between the logarithms of the Qo values calculated from the definition of Zutty and Burkhart (122) and the logarithms of the rates of addition of ethyl radicals to various substituted ethylenes. Similar... 

Data for 21 sets of reaction rates have been correlated with eq. (2) or eq. (30). Also correlated were data on the meta para ratio in the product of the reaction of isoprene with substituted ethylenes, and the syn-exo-anti-endo and... 

The magnitude of the localized electrical effect in the case of the substituted ethylenes is the same as that of the substituted acetylenes. The latter are significantly more susceptible to resonance effects than are the former, however. 

Dipole moments of substituted nitriles were correlated with the a constants by Taft and with the Op constants by Charton (18). In addition to dipole moment data, some information is available on the C=N stretching frequencies of substituted nitriles. The sets studied are reported in Table XXXVI. Results of the correlations with eq. (2) are given in Table XXXVII, and values of Pr are set forth in Table XXXVIII. The correlation of the dipole moments of substituted nitriles with eq. (2) gave significant results, which were very much improved by the exclusion of the value for X=I (set 36-1-2). In contrast to the results obtained for substituted ethylenes, acetylenes, and benzenes, the value of /3 obtained for dipole moments of substituted nitriles is not significant. The value of a obtained for the substituted nitriles is comparable to the value of a observed for the substituted acetylenes. 

---