Butenal trans-Crotonaldehyde

Trans-2-Butenal (trans-Crotonaldehyde). Pitts and coworkers (2,58) investigated the photolysis of trans-crotonalde-hyde in the gas phase to correlate the structural effects on photodecomposition and reactivity of a, (5-unsaturated aldehydes. As in the case of acrolein, this molecule showed an unusual stability, except polymerization being the only significant reaction at 265-254 nm and 25°C (2). Some reactions giving 

Coomber and Pitts (58) extended the abovementioned work by a study at wavelengths longer than 255 nm and 70-130°C. They found that (1) the major photodecomposition products were CO and propylene, and (2) small amounts of ethylene, allene, methyl-acetylene, cyclopropane, ethylketene, and enol-crotonaldehyde were also formed. Experiments with long-path infrared spectroscopy (LPIR) have shown that the quantum yields of ethylketene were 0.02 at X 280 nm and -0.001 at X 300 nm, whereas the quantum yields of enol-crotonaldehyde were very small at X  

280 nm and -0.01 at X 300 nm. The S] —/ AA- Sq internal conversion via photoisomerization to unstable intermediates was proposed as the mechanism of important radiationless processes. 

It should also be mentioned that Allen and Pitts (1) studied the CH3-radical-sensitized decomposition of trans-crotonaldehvde to show that the 2-butene formation observed in the earlier photolysis studies is due to methyl-radical displacement of the formyl group. 

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SYNS ALDEHYDE CROTONIQUE (FRENCH) trans-2-BUTENAL (E)-2-BUTENAL CROTONAL CROTONALDEHYDE CROTONIC ALDEHYDE 1,2-ETHANEDIOL DIPROPANOATE (9C1) ETHYLENE GLYCOL DIPROPIONATE (SCI) ETHYLENE PROPIONATE p-METHYL ACROLEIN NCI-C56279 PROPYLENE ALDEHYDE RCR.Y WASTE NUMBER U053 TOPANEL... 

Ordinary Grignard reagents react with a, -unsaturated carbonyl compounds and afford both 1,2-adduct and 1,4-adduct. However, methylsulfonyhnethylmagnesium bromide or p-tolylsulfonylmethylmagnesium bromide gave only 1,2-adducts in the reaction with conjugated carbonyl compounds such as crotonaldehyde, cinnamaldehyde, trans-4-phenyl-3-buten-2-one, benzalacetophenone and l,5-diphenyl-2,4-pentadien-l-one. 

There are some cases where both types of photocycloaddition take place. For example, cinnamaldehyde and crotonaldehyde yield, upon irradiation with 2-methyl-2-butene, both the oxetane and the cyclobutane products.26 In marked contrast, mesityl oxide, as similar as it would appear to be to crotonaldehyde (Table I), is stable to irradiation in the presence of both isobutylene and isopropanol.37,74 These differences in reactivity of a,/9-unsaturated carbonyl compounds have been attributed to conformational (that is, s-cis or s-trans) differences.74... 

Several water-soluble ruthenium complexes, with P = TPPMS, TPPTS, or PTA ligands (cf. Section 2.2.3.2), catalyze the selective reduction of crotonaldehyde, 3-methyl-2-butenal (prenal), and trans-cinnamaldehyde to the corresponding unsaturated alcohols (Scheme 2) [33—36]. Chemical yields are often close to quantitative in reasonable times and the selectivity toward the aUyhc alcohol is very high (> 95%). The selectivity of the reactions is critically influenced by the pH of the aqueous phase [11] as well as by the H2 pressure [37]. The hydrogenation of propionaldehyde, catalyzed by Ru(II)/TPPTS complexes, was dramatically accelerated by the addition of inorganic salts [38], too. In sharp contrast to the Ru(II)-based catalysts, in hydrogenation of unsaturated aldehydes rhodium(I) complexes preferentially promote the reaction of the C=C double bond, although with incomplete selectivity [33, 39]. 

Crotonaldehyde — Chemical Designations — Syru)-nyms Beta-Methylacrolein Crotenaldehyde Crotonic Aldehyde Trans-2-Butenal Chemical Formula CH3CH=CHCH0 (ii) Observable Characteristics—... 

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