FORMATION FROM OLEFINS

K. A. Cooper, E. D. Hughes, and C. K. Ingold, "The Mechanism of Elimination Reactions. Part III. Unimolecular Olefin Formation from Tert.-Butyl Halides in Acid and Alkaline Aqueous Solutions," JCS 140 (1937) 1280. 

Olefin formation from aldehydes and phosphonates. Workup is more advantageous than the corresponding Wittig reaction because the phosphate by-product can be washed away with water. 

The different degrees of water inhibition on the ether and olefin formation from ethanol on alumina, and the agreement of ether/ethylene selectivity ratios found experimentally with those calculated by the Monte Carlo simulation of the hydrated surface of alumina [144],... 

The physical properties of most acids (esters) and alcohols allow the reaction to be carried out either in the liquid or in the vapour phase. In the liquid phase, the effects of solvents and of transport phenomena may play a more important role than in the vapour phase. On the other hand, the side reactions (mainly the ether and/or olefin formation from the alco- TABLE 20 Reactants and inorganic catalysts used in kinetic studies of esterification (transesterification) ... 

Fig. 14. Taft correlation with polar substituent constants (a ) of the vapour phase esterification of acetic acid with alcohols ( ) and of the olefin formation from alcohols (O) over Na-poisoned silica—alumina at 250°C [126]. 1, Methanol 2, ethanol 3, 1-propanol 4, 1-butanol 5, 2-methyl-l-propanol 6, 2-propanol 7, 2-butanol 8, 2-methyl-2-propanol.

Scheme 4 Possible reactions of the intermediates formed after photolysis of 3-aryl-3//-diazirines. Inset shows olefin formation from carbene derivative of unsubstituted 3-alkyl-3//-diazirines via a hydride shift...

FIG. 7. Rate of olefin formation from isobutanol at 220°C on 6-AI2O3 [expressed as olefin pressure (mm Hg) formed at constant contact time] versus integrated band area (arbitrary units) of band at 2870 cm-1. [Reproduced with permission from Knozinger and Stolz (47).]... 

A syn-elimination of Ph2MeP=0 and simultaneous stereoselective olefin formation from an oxaphosphetane are shown in Figure 4.40 (note that this oxaphosphetane is... 

The catalyst is based on high levels of a ZSM-5 type zeolite which has been doped with a combination of phosphorus, magnesium and calcium. This type of formulation has been used to produce ethylene and propylene from methanol and is known to promote olefin formation from a wide variety of feeds. ... 

The effect of coke deposition on the MTO reaction is complex. Coke deposition influences either the formation of dimethyl ether (DME) or the DME conversion inside the pores during MTO. However, the effect of coke deposition on the dimethyl ether conversion to light olefins (the DTO process) catalyzed by SAPO-34 is much simpler and can allow us to focus on the effect of intracrystalline coke on the olefin formation from DME. 

The four-coordinate sqnare planar iron(n) porphyrins discussed above are not only of great valne in heme protein model chemistry, but also in chemical applications, since they undergo a wealth of ligand addition reactions. For example it has been shown that TPPFe complexes are active catalysts for important carbon transfer reactions in organic chemistry and are found to catalyze the stereoselective cyclopropanation of aUcenes, olefin formation from diazoalkanes, and the efficient and selective olefination of aldehydes and other carbonyl compounds. The active species in these carbon transfer reactions are presumably iron porphyrin carbene complexes. " It was also found that ferrous hemin anchored to Ti02 thin films reduce organic halides, which can pose serious health problems and are of considerable environmental concern because of their prevalence in groundwater. ... 

D-Glucose ([52], Fig. 9) has served as an intriguing educt for preparation (31) of the Corey lactone equivalent [59] (32). The iodo compound [53] was readily available from glucose in four steps. Reductive fragmentation, induced by zinc in ethanol, gave the unsaturated aldehyde [54]. Reaction with N-methylhydroxylamine was followed by a spontaneous nitrone cycloaddition to provide the oxazolidine [55]. Catalytic reduction of the N-O bond was accompanied by the unexpected loss of tosylate and aziridine formation. Olefin formation from [56] via the N-oxide and chain extension gave acid [57]. lodolactonization and tri-n-butyltin hydride reduction in the standard fashion led to lactone [58]. After saponification of the benzoates, stereoselective epoxide formation gave epoxy lactone [59]. 

Regioselective olefin formation from ketones has been exploited. Conversion of ketones to the corresponding enol diphenylphosphates and subsequent coupling of... 

We have also examined olefin formation from higher alkanes. Propane and butane also produce up to 70% selectivity to olefins on Pt monolith ceramic foam monoliths at nearly 100% O2 conversion with alkane conversions of typically 80% at comparable flow rates and catalyst temperatures to those used for C2H6. However, olefins from these higher alkanes exhibit considerable cracking, with C2H4 the dominant product except at low temperatures and excess fuel. However, isobutane produces primarily isobutylene and C3H6 with litde C2H4. 

The temperature effect on the dehydration of alcohols in the presence of alumina as has been shown by the work of Sabatier and Mailhe,41 Brown and Reid,°°b and Pease and Yung08 was not checked by Adkins,° b who used what were presumably better conditions experimentally. The rate of dehydration increases in the order of butyl, propyl, isobutyl, ethyl, isopropyl, and secondary butyl alcohols. Although ethanol and ethyl ether give the same rate of dehydration, butyl alcohol gives a faster dehydration late than does butyl ether. Hence, the hypothesis advanced at one time that olefin formation from alcohols was through intermediate ether formation cannot hold. 

KUHN WINTERSTEIN Olefmatlon Olefin formation from glycols by means of P2 U... 

The orientational behaviour of amine oxide pyrolyses has been adequately summarised by Cope and TrumbulE . As for the acetate decompositions, orientation in the simple alkyl systems is controlled primarily by statistical factors but departure from this influence is noted with the bulky r-butyl substituent and the acid strengthening beta phenyl substituents Eclipsing effects are greater in the planar five-membered transition states than in the puckered six systems and this is borne out by the greater preference for trans-olefin formation from amine oxides than esters and xanthates (152, cf. 149). 

R = H. Ph From polystyryl diphenylphosphine cross linked with 2, S and 20% DVB. - Comparison of olefin formation from aldehydes and ketones using polymeric phosphonium halides with different degree of crosslinking. 

Hydroboration of imines of cyclohex-2-enones has also been investigated. Regiospecificity in olefin formation from toluene-p-sulphonylhydrazones and methyl-lithium is clearly seen. Thus the anti-hydrazone (44) gave the diene (45a) whereas the syn-hydrazone gave a mixture of (45a) and (45b). Several solvent systems were investigated but results showed that the hydrazone stereochemistry had a consistent effect, and that syn anti isomerism was not in operation. 

Pyrolysis of the xanthate or acetate is the normal method for olefin formation from alcohols, which avoids carbonium ion intermediates. In the case of... 

Modification of ZSM-5 zeolites with various compounds is also effective. Kaeding and Butter reported that ZSM-5 modified by treatment with phosphorus compounds showed high (70%) selectivity to Ci — C4 olefin formation from methanol. This could also be ascribed to decrease in stronger acid sites by the treatment. 

At high Si02/Al203 (> 70) and with suitable adjustment of reaction temperature and eontaet time to provide eomplete eonversion, it has been found possible substantially to decouple olefin formation from aromatization. This mode of operation is the basis of the methanol-to-olefms (MTO) process (see later). 

The dual-cycle mechanism, recently introduced by Svelle et al. afto confirmation by theoretical calculations [91], combines the features of both mechanistical approaches (Fig. 14) [29,92,93]. This mechanism represents the most recent state on olefins formation from methanol and allows the best fitting with the experimental data. 

Baudin JB, Hareau G, Julia SA, Ruel O. Stereochemistry of the olefin formation from anti and syn heterocyclic (3-hydroxy-sulfones. Bull. Soc. Chim. Fr. 1993 130(3) 336-357. 

Thus, a reaction involving water addition not being demonstrable, propylene presumably is eliminated as an intermediate. In the only other case of olefin utilization involving direct primary attack of the double bond, the product was a 1,2-diol (page 254). Demonstration of olefin formation from alkane in the system of Senez and Azoulay would be an important advance. Another important question about their Pseudomonas aeruginosa system is whether the l-ol would be formed from the suspected 1-ene intermediate, and if so—how. 

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