Atomic cinnamic acid

In general, condensation takes place at the a-carbon atom, leading to simple cinnamic acids or to their a-substituted derivatives. When possible, the anhydride corresponding to the sodium sail should be the condensing agent. 

The a-carbon atom of the phenylacetyl group is more susceptible to attack by the basic catalyst (triethylamine) than the acetyl group hence a-phenyl-cinnamic acid, but no cinnamic acid, is obtained. 

Cinnamic Acid.—The reaction, which takes place when an aldehyde (aliphatic or aromatic) acts on the sodium salt of an aliphatic acid in presence of the anhychide, is known as Perkin s reaction, and has a ery wide application. Accoid-ing to the result of Fittig s researches on the properties of the unsaturated acids described below, the reaction occurs in two steps. The aldeh) de forms first an additive compound with the acid, the aldehyde caibon attaching itself to the n-carbon ii.e.i nevt the carbovyl) of the acid. A saturated hydiOKy-acid is formed, which is stable, if the a-carbon is attached to only one atom of hydrogen, as in the case of isobutync acid,... 

Simandi and Nagy studied the kinetics of the catalyzed hydrogenation of cinnamic acid (S) to dihydrocinnamic acid (SHj) under steady-state conditions 166). They concluded that the kinetically important reactions were the two successive transfers of hydrogen atoms, viz.. 

In this reaction the carbanion (103) is obtained by removal of an ot-H atom from a molecule of an acid anhydride (104), the anion of the corresponding acid acting as the necessary base the carbonyl acceptor is pretty well confined to aromatic aldehydes. The products are a/J-unsaturated acids, e.g. 3-phenylpropenoic(cinnamic) acid (105) from PhCHO/excess (MeC0)20/MeC02e at 140° ... 

A great number of olefinic compounds are known to photodimerize in the crystalline state (1,2). Formation of a-truxillic and / -truxinic acids from two types of cinnamic acid crystals was interpreted by Bernstein and Quimby in 1943 to be a crystal lattice controlled reaction (5). In 1964 their hypothesis on cinnamic acid crystals was visualized by Schmidt and co-workers, who correlated the crystal structure of several olefin derivatives with photoreactivity and configuration of the products (4). In these olefinic crystals the potentially reactive double bonds are oriented in parallel to each other and are separated by approximately 4 A, favorable for [2+2] cycloaddition with minimal atomic and molecular motion. In general, the environment of olefinic double bonds in these crystals conforms to one of three principal types (a) the -type crystal, in which the double bonds of neighboring molecules make contact at a distance of -3.7 A across a center of symmetry to give a centrosymmetric dimer (1-dimer) (b) the / -type crystal, characterized by a lattice having one axial length of... 

It is well established, in a qualitative sense, that chemical reactions occurring in crystals are subject to restrictive forces, not found in solution, which limit the allowable range of atomic and molecular motions along the reaction coordinate. This often leads to differences, either in the product structures or the product ratios, in going from solution to the solid state. This was first demonstrated in a systematic way by Cohen and Schmidt in 1964 in their studies on the solid state photodimerization of cinnamic acid and its derivatives (1 ). This work led to the formulation of the famous topochemical principle which states, in... 

The electron-rich oxygen atom of a secondary amide derivative of cinnamic acid can be as effective as that of a cinnamyl ether or alcohol in directing anr/-Michael additions to some amide Michael acceptors. For example, BuLi adds to the amide 51 to give a 90 10 ratio of anti-Michael Michael addition products 52 53.31 With the alkyne54 the effect is even more pronounced MeLi gives solely the anti-Michael product 55. These reactions are however very sensitive to starting material and reagent structure. 

According to an atom chain, in which the cinnamic acid is indicated by A,... 

According to another hypothesis frequently suggested, the bromine atoms combine with bromine molecules to give triatomic bromine molecules which are rather unstable and after reaction they regenerate the bromine atoms, ready to repeat the cycle. This chain was applied to the photobromination of cinnamic acid by Purka-yastha and Ghosh.41... 

If these chemical chains involving Br or Br3 were ruled out, one could consider an energy chain, in which the exothermic heat of reaction plus the energy of excitation is sufficient to produce the dibromide of cinnamic acid with a high energy content. The heat of bromination alone is estimated at 16,000 calories. These hot molecules of product then pass their energy over to more bromine atoms which then react to form additional dibromide, as follows,... 

Fig. 8. Photodimerization in o-ethoxy cinnamic acid Two centrosymmetric molecules of the a-form before (full lines) and after (dashed lines) the reaction. Hydrogen atoms other than the hydroxyl are omitted for the sake of clarity. The cinnamoyl double bonds are spaced at —4.3 A and following the cycloaddition, a new pair of bonds is formed which are slightly longer (—1.57 A) than typical C-C bonds. The inset shows the deformation density (at 0.075 ek 3) in the plane of the cyclobutane ring in the a-dimer.

Scheme 5 lists chemical shift values of hydrogen atoms in compounds 13 and 16. From these data, it is suggested that the slight deshielding of H(a) in compound 13 relative to 16 can be easily attributed to the effect of 2-cinnamic acid. In other... 

Perimargine (152) and dihydroperimargine (153) isolated as an inseparable mixture were converted to a simple product by catalytic hydrogenation. Because of the similarity of the spectral data to that of alkaloids of the dihydroperiphylline group, structure 152/153 was proposed. In addition, alkaline hydrolysis gave ( )-cinnamic acid and an unstable organic acid that was isolated but not identified. The substituent at N-6 is therefore characterized in terms of atomic mass units (114). 

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