FUNCTIONAL GROUP CONTENTS Aldehydes

A combination of analytical techniques has to be used to fully characterize an amino resin molar ratios of amino compound to aldehyde and alcohol, molecular mass, molecular mass distribution, and functional group content are important data. 

It is noteworthy that no evidence for unfrmctionalized polystyrene homopolymer was found when these functionalized polymers were examined by TLC. Control experiments have shown that as little as l-2wt.% of the unfrmctionalized polystyrene can be detected using this TLC technique. The co-formyl functional group content was determined by aldehyde end-group titration to range from 0.90 to 1.00 for polystyrene molecular weights in the range of 2000-8100 gmol" ... 

Reduced dextran dialdehydes. The reaction of dextran (D-OH) with sodium metaperiodate is a two step reaction leading to different kinds of aldehyde functions. Although the aldehyde content can not be precisely predicted from the amount of periodate added, by approximation 1.5 equivalents of periodate are required per dialdehyde structure. By varying the amount of periodate added to the polysaccharide dextran dialdehydes with variable degree of oxidation were obtained. In order to avoid interaction of the polyaldehyde (D-CH=0) with the dextranases the aldehyde groups were subsequently reduced by reaction with sodium borohydride ... 

The carbonyl group in aldehydes (RCHO) and ketones (RCOR ) is one of the frequently encountered functionalities in the composition of organic compounds. This group has no active hydrogen atoms, excluding the cases of high content of enols for /3-dicarbonyl compounds (/3-diketones, esters of /3-ketocarboxylic acids, etc.) ... 

This method was used to determine the content of various organic functional groups (amines, alcohols, phenols, aldehydes, ketones, carboxyl, insaturation, allylic/benzylic sites) in kerogens of Brazilian oil shales. The results (26) indicate the Tremembe Formation as being the most functi.onatTzed while Irati is the least. This is in accordance with the accepted trend that functionalizations correlates with maturity. 

The content of aldehyde and ketone groups reaches 42% during the thermal oxidation of polypropylene, and 35—44% in polyethylene [5, 7]. This content depends on the conditions of the oxidation, particularly the temperature. The quantitative distribution of various functional groups formed during the oxidation of polyolefines is shown in Table 2. 

The use of an acidic solution of p-anisaldehyde in ethanol to detect aldehyde functionalities on polystyrene polymer supports has been reported (beads are treated with a freshly made solution of p-anisaldehyde (2.55 mL), ethanol (88 mL), sulfuric acid (9 mL), acetic acid (1 mL) and heated at 110°C for 4 min). The colour of the beads depends on the percentage of CHO content such that at 0% of CHO groups, the beads are colourless, -50% CHO content, the beads appear red and at 98% CHO the beads appear burgundy [Vdzquez and Albericio Tetrahedron Lett 42 6691 200]]. A different approach utilises 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (Purpald) as the visualizing agent for CHO groups. Resins containing aldehyde functionalities turn dark brown to purple after a 5 min reaction followed by a 10 minute air oxidation [Coumoyer et al. J Comb Chem 4 120 2002]. 

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