Aldehydes from 2 molecules

These results indicate that the same crystalline face does not necessarily exhibit the same catalytic properties with different molecules. Thus, the (010) face of a-Mo03 is selective for the formation of aldehydes from alcohols while it promotes essentially the deep oxidation of olefins. It is expected that the studies on structure-sensitive reactions will be made more quantitative using recent methods to determine the number of surface M=0 species (425 —7). It should be noted that the earlier observation on the specificity of Mo03 crystalline faces in propylene oxidation has been obtained on oriented Mo03-graphite catalysts (425k). Non-structure-sensitive reactions have also been reported (425k). 

To demonstrate that optically active aldehydes from formylation of the methyl groups of optically active olefins can be obtained as main reaction products with good optical yields, we have studied the hydroformylation of ( + )(S)-2,2,5-trimethyl-3-heptene. None of the methyl groups of the tertiary butyl group were carbonylated. Primarily the reaction product was from carbonylation of the other two methyl groups present in the molecule (Table 1). (S)-3-Ethyl-6,6-dimethylheptanal... 

In simple molecules, it is possible to obtain a good yield of aldehyde— including examples possessing an important proportion of hydrate in equilibrium—by continuous distillation of the aldehyde from the reaction mixture.73 This procedure only succeeds in the preparation of simple volatile aldehydes. 

It is worth noting that, in being converted into acrylamide, the Strecker aldehyde from asparagine needs to have a hydroxy group reduced as well as to lose a molecule of water. 

A group used to prevent a sensitive functional group from reacting while another part of the molecule is being modified. The protecting group is later removed. For example, an acetal can protect a ketone or an aldehyde from reacting under basic or neutral conditions. Dilute acid removes the acetal, (p. 860)... 

Strategy Both sets of reactants cleave double bonds. Aqueous KMn04 produces a carboxylic acid from a double bond carbon that is monosubstituted and a ketone from a double bond carbon that is disubstituted. Ozone produces an aldehyde from a double bond carbon that is monosubstituted and a ketone from a double bond carbon that is disubstituted. If the double bond is part of a ring, both carbonyl groups occur in the same product molecule. 

J. Grobe, C. Bruning, M. Wessels, "Aldehyde-functionalized Silanes New Compounds to Improve the Immobilization of Biomolecules", in Organosilicon Chemistry II From Molecules to Materials (Eds. N. Auner, J. Weis), VCH, Weinheim, 1996, p. 243. 

The activation energy values for olefine oxidations are summarized in Table VIII. The activation energy for carbon dioxide generation, ECOi, is higher than those for carbon monoxide and aldehyde (Ec0 and E ). Eco increases with an increasing number of carbon atoms in the hydrocarbon molecule. The activation energies for the formation of aldehydes from propene and isobutene are low and close to each other. 

Like proteins, carbohydrates occur in almost bewildering varieties. Many of the most important carbohydrates are polymers— large molecules constmcted by hooking together many smaller molecules. We have seen that proteins are polymers constmcted from amino acids. The polymeric carbohydrates are constmcted from molecules called simple sugars or, more precisely, monosaccharides. Monosaccharides are aldehydes or ketones that contain several hydroxyl (—OH) substiments. An example of a monosaccharide is fmctose, with the stmcmre... 

Solution The functional group which differentiates an aldehyde from other organic molecules is a carbonyl atom (C=0) joined to another carbon atom and to a hydrogen atom. In general, the formula for an aldehyde is... 

FIGURE 7.15 The spectra of a series of polyene aldehydes. (From Murrell, J. N., The Theory of the Electronic Spectra of Organic Molecules, Methuen and Co., Ltd., London, 1963. Reprinted by permission.)... 

The amount of aldehyde groups is usually used for evaluation of the intensity and efficiency (number of chain scissions per molecule of reacted ozone) of ozone degradation of elastomers. In this case, it should be taken into account that the dominant route of degradation leads to the formation of 1 mole of aldehyde from 1 mole of ozone [32]. 

Thus, in the first operation, 31 was treated with ceric ammonium nitrate (CAN) in aqueous MeCN to effect the oxidative conversion of its C-ring into a quinone, an event attended by the concomitant scission of its B-ring to afford a hydroxymethyl function in the product (30). However, since a residual aldehyde from the Diels- Alder reaction was present on the same side of the A-ring as this newly generated alcohol, the isolated product was not 30, but instead was lactol 74. Although this latter ring closure was not critical for the operations ultimately needed to reach 28, it did serve to protect the oxidized substrate (30) from the action of excess CAN. For example, only decomposition resulted when the exo Diels—Alder variant of 31 was subjected to the same conditions, presumably because the hydroxymethyl function that was produced in this case could not form a lactol since its aldehyde partner was on the opposite side of the molecule. 

In these first experiments, starting from several aldehyde acceptor molecules 2a-c, the Mannich products 8a-c were obtained in moderate to good yields and generally high enantioselectivity after 12 h of stirring in a mixture of acetone and DMSO (Scheme 5.2). Some side-products were also formed due to competing aldol reactions and subsequent condensations thereby accounting for the somewhat lower yields. 

Aldol condensation, on the other hand, is favorably carried out over basic oxygen sites on the Ti02 smface and does not appear to require coordinatively unsaturated Ti sites. The reaction is thought to proceed initially by the proton abstraction at the carbonyl carbon from the aldehyde reagent molecule by a basic oxygen site on the surface... 

Oxidative cleavage of 1,2-diols with periodie acid or with lead tetraacetate gives aldehydes or ketones 23,24,25,26,27,39,44,46. A molecule with a particular functional group can be prepared from molecules containing different functional groups by a series of chemical steps (reactions). This process is called synthesis The new molecule is synthesized from the old one (see Chapter 25) 28, 29, 30, 37, 45, 46, 47, 48. 

Iron(III) chloride forms numerous addition compounds, especially with organic molecules which contain donor atoms, for example ethers, alcohols, aldehydes, ketones and amines. Anhydrous iron(III) chloride is soluble in, for example, ether, and can be extracted into this solvent from water the extraction is more effective in presence of chloride ion. Of other iron(III) halides, iron(III) bromide and iron(III) iodide decompose rather readily into the +2 halide and halogen. 

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