Phenol aldehydes, table

Table I. Amounts of Phenolic Acids and Phenolic Aldehydes Released from Graminaceous Cell Walls by Treatment with Sodium Hydroxide...

The following tables are intended to include all the reductions with aluminum alkoxides which were reported prior to February, 1943, although some examples doubtless have been overlooked. Table I lists the reduction of aldehydes, which have been subdivided into (a) aliphatic aldehydes and (b) alicyclic and aromatic aldehydes. Table II lists the reduction of ketones, which have been classified as (a)-satu-rated and unsaturated aliphatic ketones, (b) aromatic ketones, (c) alicyclic ketones, (d) unsaturated alicyclic and aromatic ketones, (e) a- — halogen substituted ketones, (f) diketones, (g) protected diketones, (h) alcoholic and phenolic ketones (and ethers or esters of these), and (i) keto esters. 

Table 6.2.7. Yields of phenolic aldehydes from several plant species and their lignin preparations on nitrobenzene oxidation (yield in mol % 1C, unit)1... 

Table 13.22. Impact of toasting intensity on the formation of phenol aldehydes (Chatonnet, 1995)...

Phenolic aldehydes and ketones. The Rf values of phenolic aldehydes as their phenylhydra-zones formed in situ have been determined on silica gel G and kieselguhr G (in equal parts) in four different solvents (108) and on cellulose in four different solvents. The collected results for a number of hydroxy and methoxy compounds are shown in Table 13. The Revalues for various hydroxybenzo-phenones and hydroxydiphenylmethanes on silica gel G (F-254) have been determined in the five solvents shown in Table 14 (109). The figures show both the presence of hydrogen bonding and its suppression as a factor either by the solvent or by the intervention of another polar group. 

Table 13 Rf Values of Phenolic Aldehydes on Silica Gel G and on Cellulose... 

The effect of the aldehyde group on the phenoHc hydroxyl group is primarily an increase in its acidity both 2-hydroxy- and A- diX< > Lyben ldehydes are stronger acids than phenol (pK 20°C) = 9.89 see Table 2 for comparison). The aldehyde group, however, has Httie effect on the reaction of the... 

Adolph Baeyer is credited with the first recognition of the general nature of the reaction between phenols and aldehydes in 1872 ([2,5-7] [18], Table 5.1). He reported formation of colorless resins when acidic solutions of pyrogallic acid or resorcinol were mixed with oil of bitter almonds, which consists primarily benzaldehyde. Baeyer also saw resin formation with acidic and basic solutions of phenol and acetaldehyde or chloral. Michael and Comey furthered Baeyer s work with additional studies on the behavior of benzaldehyde and phenols [2,19]. They studied a variety of acidic and basic catalysts and noted that reaction vigor followed the acid or base strength of the catalyst. Michael et al. also reported rapid oxidation and darkening of phenolic resins when catalyzed by alkaline materials. 

The chemical composition of the produced oil was analyzed by GC-MS. The samples were prepared by diluting the bio oil in methanol in a way that the fraction of organic oil was the same in each GC-vial. The products found in the oil were grouped as aldehydes, acids, alcohols, ketones, phenols, polyaromatics and others. The most interesting groups are shown in Table 4 and Table 5, arranged according to their retention time (RT). The procedure for the GC-MS analysis has been previously reported by the authors [4],... 

In Table 15 are recorded the dissociation constants of certain phenolic compounds. From these data it becomes obvious that the introduction of aldehyde groups, or other substituents, changes the dissociation constant of phenolic hydroxyls by over one-hundred fold. Moreover, oxidation studies carried out in this laboratory have shown that the native lignins from bagasse, white Scots pine and birch contain... 

Various aldehydes 184 and alcohols have been shown to be competent in the redox esterification of unsaturated aldehydes in the presence of the achiral mesityl triazo-lium pre-catalyst 186. Both aromatic and aliphatic enals participate in yields up to 99% (Table 13). Tri-substituted enals work well (entry 3), as do enals with additional olefins present in the substrate (entries 4 and 7). The nucleophile scope includes primary and secondary alcohols as well as phenols and allylic alcohols. Intramolecular esterification may also occur with the formation of a bicyclic lactone (entry 8). 

In 2005, Rovis and Reynolds reported the synthesis of a-chloroesters from a,a-dichloroaldehydes using chiral, enantioenriched not chirald pre-catalyst 75c [115], As shown in Table 14, the reaction scope includes a variety of dichloroaldehydes 201 that afford desired esters 202 in good yields and enantioselectivities. The reaction is compatible with various phenols, including electron-rich and electron-poor nucleophiles. Standard reaction conditions accommodate a variety of aldehydes, although substrates containing P-branching inhibit reactivity. 

Phenolic acids and aldehydes released from graminaceous cell walls by treatment with alkali are shown in Figure 1. Examples of the amounts released from various cell walls are listed in Table I. 

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