Trans-Crotonic acid

A derivative from trans-crotonic acid via quinine salt resolution... 

Substrates 4-9 were chosen by Freeman to study the influence of steric bulk on the free activation energy. As discussed before the substituents also show an electronic effect and it is hard to separate both effects, but at least some comparisons can be made, e.g., for trans-crotonic acid 4 and 4,4-dimethyl-trans-2-pentenoic acid 9. The steric bulk of the t.-butyl group compared to a methyl group should be by far more important than the difference in the electronic effect. 

DIHYDROFURAN DIVINYL ETHER METHACROLEIN 2-BUTYNE-1,4-DIOL ganna-BUTYROLACTONE cis-CROTONIC ACID trans-CROTONIC ACID METHACRYLIC ACID METHYL ACRYLATE VINYL ACETATE ACETIC ANHYDRIDE SUCCINIC ACID DIGLYCOLIC ACID MALIC ACID TARTARIC ACID n-BUTYRONITRILE ISOBUTYRONITRILE ACETONE CYANOHYDRIN... 

Fig. 9.3. The pair of reactions illustrates the occurrence of stereoselectivity and the lack of stereospecificity in two cyclopropanations with an S ylide. The trans-crotonic acid methyl ester reacts with complete retention of the configuration, whereas the di-crotonic acid methyl ester reacts with complete inversion.

Freeman chose substrates D-I to study the influence of steric bulk on the free energy of activation for the permanganate dihydroxylation. It is difficult to separate these substituent effects on the reaction rate, because it is not clear how to determine the relative contributions of steric and electronic effects to the overall observed effect. However, some comparisons are useful. For example, in the case of trans-crotonic acid D and 4,4-dimethyl-fra/rv-2-pentenoic acid I the large bulk of the t-butyl group compared to that of a methyl group should result in a dominance of the steric over the electronic substituent effect. 

The model test sample is uniformly enriched trans-crotonic acid. The methyl (SI) resonance is well separated from the two carbonyl lines. The closest carbonyl, S2, is spatially two bonds away, while S3 is directly bonded (Fig. 6). The usual spin phase encoding is stored after ti evolution in the z direction, whereupon the rotation speed is changed to sweep, in this case sequentially over the rotational resonance between methyl and both carbonyl sites. The mixing flowchart is thus composed of a sequence of passing rotational resonance... 

Fig. 8 Rotation sweep spectra of trans-crotonic acid at two different sweep rates...

Quantitative studies of the effect of pyridine on the rate of hydrogenation of trans-crotonic acid in the presence of a platinum catalyst have been carried out by Maxted and Walker39 who concluded that... 

Beilstein Handbook Reference) BRN 1719943 2-Butenoic acid, (Ej- (E)-2-Butenoic acid trans-2-Butenoic acid (E)-Crotonic acid Crotonic acid, (E)- trans-Crotonic acid EINECS 203-533-9 NSC 8751. Synthesis of resins, polymers, plasticizers, drugs. Prisms or needles mp = 72° bp = 184.7° d = 0.9604 very soluble in H2O (54.6 g/l), EtOH, soluble in Et20, Me2CO, ligroin LD50 (rat orl) n 1.0 g/kg. Alcoa Ind. Chem. Allchem /nd. Chisso Corp. USA Eastman Chem. Co. Sigma-Aldhch Fine Chem. 

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