Problems acrolein production

Solution 3.2a. The first step in examining this problem is to plot carbon deposition (the response variable) as a function of acrolein production rate, which is shown in Figure E3.2Sa. 

The early practical application of antioxidants was connected with the development of rubber production. The rubber is easily oxidized in air, and the first antioxidants were empirically found and used to stabilize it [1]. Empirical search for antioxidants was performed by Moureu and Dufresse [2] during the First World War. These researchers successfully solved the problem of acrolein stabilization by the addition of hydroquinone. They explained the retarding action of the antioxidant in the scope of peroxide conception of Bach and Engler (see Chapter 1). They proposed that the antioxidant rapidly reacts with the formed hypothetical moloxide and in such a way prevents the autoxidation of the substrate. 

There are a very large number of patented processes for the synthesis of pyridines, often in very small yields, from ketones and ammonia. Most of the syntheses must involve the condensation of two molecules of the carbonyl compound to give an a,/3 -unsaturated aldehyde or ketone, and such unsaturated compounds can be used directly. The early work on the vapour-phase catalytic processes dates from the 1920s and a series of papers by Chichibabin. In one of these (24JPR(107)154) he records the use of acrolein, acetaldehyde, and ammonia over an alumina catalyst at 370-380 °C to give a poor yield of pyridine and a very poor yield of 3-methylpyridine. The major problems are to separate the mixtures of products from the considerable amount of tarry material. Many catalysts and many mixtures of ketones have since been used a few of the better yields are reported here. 

Problem 23.17 What products would result (after hydrolysis) from reaction of the enamine prepared from cyclopentanone and pyrrolidine with the following a, -unsaturated acceptors (a) Ethyl propenoate (b) Propenal (acrolein)... 

Answer A. The symptoms are those of a mild case of hemorrhagic cystitis. Bladder irritation with hematuria is a fairly common complaint of patients treated with cyclophosphamide, It appears to be due to acrolein, a product formed when cyclophosphamide is bioactivated by liver P450 to form cytotoxic metabolites. Urinary tract problems may also occur with methotrexate from crystalluria due to its low water solubility. 

PROBLEM 18.15 Acrolein (CH2=CHCH=0) reacts with sodium azide (NaNs) in aqueous acetic acid to form a compound, C3H5N3O in 71% yield. Propanal (CH3CH2CH=0), when subjected to the same reaction conditions, is recovered unchanged. Suggest a structure for the product formed from acrolein, and offer an explanation for the difference in reactivity between acrolein and propanal. 

PRACTICE PROBLEM 19.20 When acrolein (propenal) reacts with hydrazine, the product is a dihydropyrazole ... 

The first spontaneous curing of acrolein observed was also the first polymerization in bulk [3]. Later, this observation was examined more closely [4—6,50-52]. Furthermore, a slow light- or y-ray-initiated polymerization is possible, yielding highly cross-linked glassy products [46,53,54]. By means of AIBN or peroxides as initiators an explosive course of the reaction is observed that causes problems in the carriage of the reaction heat [42,55]. Therefore, working with only small amounts is recommended. 

Thirdly, a problem with all allylic peroxides, but particularly severe here, the product a,3-unsaturated aldehyde (or ketone) polymerizes, incorporating other interesting products as well as some undecomposed hydroperoxide. The polymerization of acrolein by itself is gloriously complicated, and the nonvolatile residue from thermal decomposition of allyl hydroperoxide in toluene has so far defied analysis. Since the polymer constitutes the major, if not the only, chain termination product, some knowledge of its structure is necessary in order to obtain a free radical count and determine the efficacy of reaction 15. 

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