Aldehydes, aliphatic, olefinic

In many manufacturing processes there exists the potential for aldehyde formation. Often these aldehydes occur in low concentrations in the presence of much higher levels of aliphatics, olefinics and aromatic hydrocarbons. Gas chromatography or combined gc/ms methods are often ineffective in determining aldehydes in such a matrix. Several wet chemical techniques have been devised for estimating the total aldehyde concentration in these streams, but quantitation of the individual aldehydes has remained a difficult task. 

Pincer-ligated iridium complexes have been used as homogeneous catalysts for the dehydrogenation of aliphatic polyalkenes to give partially unsaturated polymers. The catalyst appears to be selective for dehydrogenation in branches as compared with the backbone of the polymer.56 The mechanism shown in Scheme 1 has been suggested for an [IrCl(cod)]2-catalysed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols.57... 

All aliphatic olefinic hydrocarbons react with synthesis gas at 100-130° to give, as a principal product, an aldehyde or mixture of isomeric aldehydes containing one carbon atom more than the starting olefin (hydroformylation). If the reaction is conducted at 160-180°, in the presence of a sufficiently large pressure of synthesis gas, the aldehyde... 

In contrast, reaction of 2 with HCl/NaCN/ZnCl2 does not yield the expected formylation product. Instead, a mixture is obtained containing neither aldehydic nor olefinic nor aromatic protons. Treatment with HC1/A1C13 leads to aliphatic adducts of composition 2 H C16, which are reduced by Li/tert-butanol to the novel cage skeleton 10. The reaction, involving repeated transanular bond formation, is believed to proceed via the mechanism outlined below23). 

When a stream of ozonized oxygen or air, usually under 6% ozone, is passed through a solution of an olefin, such as 2,4,4-trimethyl-2-pentene, absorption occurs as fast as the ozone is introduced and no ozone escapes through the solution until all the olefin has been converted to ozonide. If an aromatic hydrocarbon such as benzene is ozonized rather than an aliphatic olefin, absorption of ozone is not complete and several times the theoretical amount of ozone must be used to effect complete ozoniza-tion. When a molecule has both an aromatic system and an aliphatic double bond, the aliphatic bond may react selectively, with little or no reaction with the aromatic system. Anethole will absorb a mole of ozone and produce, on hydrolysis of the ozonide, a very good yield of anise aldehyde. Complete saturation of the molecule requires almost 10 moles of ozone, however. 

In the preparation of a combinatorial library of a,[3-unsaturated carboxylic acids, a group from Rhone Poulenc Rorer utilized the H WE-olefination reaction. Starting from 1-substituted phosphonoacetic acid anchored to polystyrene, a 48-membered library containing a diverse set of aldehydes (aliphatic, aromatic and basic) was produced, with an (E/Z)-ratio that was highly dependant on the a-substituent of the phosphonate, where hydrogen gave a 9 1 ratio in favor of the (Ej-product... 

The intermediary aldehydes derived from the Ru-catalyzed hydroformylation can be trapped as acetals, as shown by Borner and colleagues (Scheme 1.40) [45]. Only traces of alcohols or aldehydes could be detected. The tandem reaction proceeded exclusively with diols that formed thermodynamically stable 1,3-dioxolane and 1,3-dioxane rings. Methanol as the acetalization reagent failed. As olefins, terminal aliphatic olefins as well as styrene derivatives reacted. The catalyst could be recycled and reused at least twice. 

In 1982, Okano and Kiji [13] were the first to use paraformaldehyde in excess for the hydroformylation of styrene in the presence of a Rh(hydrogencarbonate) catalyst (Scheme 3.3), aliphatic olefins, and acrylic esters. Aldehydes were formed as major products. 

Oxidation reactions are useful for the conversion of aliphatic side chains of aromatic compounds, primary alcohols, aldehydes, ketones, olefins, and a combination of one or more of the latter groups to a carboxylic acid. 

Aliphatic Aldehyde Syntheses. Friedel-Crafts-type aUphatic aldehyde syntheses are considerably rarer than those of aromatic aldehydes. However, the hydroformylation reaction of olefins (185) and the related oxo synthesis are effected by strong acid catalysts, eg, tetracarbonylhydrocobalt, HCo(CO)4 (see Oxo process). 

This ladical-geneiating reaction has been used in synthetic apphcations, eg, aioyloxylation of olefins and aromatics, oxidation of alcohols to aldehydes, etc (52,187). Only alkyl radicals, R-, are produced from aliphatic diacyl peroxides, since decarboxylation occurs during or very shortiy after oxygen—oxygen bond scission in the transition state (187,188,199). For example, diacetyl peroxide is well known as a source of methyl radicals (206). 

Olefin synthesis Irom phosphorane ylides (e g 3) with aldehydes or ketones cis olelins predominate in aliphatic systems trans m coniugated olefins... 

The catalytic system employing (2 - Fur)3P as ligand was applied to the coupling of methyl vinyl ketone and ethyl vinyl ketone to aromatic, aliphatic, acetylenic, and olefinic aldehydes (Scheme 23) [37]. Despite the hydrogenation conditions, alkyne and alkene moieties, as well as benzylic ether and nitro functional groups all remained intact. Furthermore, extremely high lev-... 

In the reactions of aliphatic carbonyl compounds with conjugated olefins a very clear distinction of mechanism is possible after comparing calculations with experimental results. Examples are shown in Eqs. 45 112,113) and 46. 114> After n-n excitation of the aldehyde the domi-... 

Aliphatic aldehydes have also been used, leading to intermediates that can undergo olefin isomerization under the action of mild base to generate metal-bound dienes these have then been used in subsequent Diels-Alder reactions, either before376 or after377-379 demetallation of the metal complex (Equation (106)). 

---