Replacement, aldehyde group

Monocarboxylic acids formally derived from aldoses by replacement of the aldehydic group by a carboxy group are termed aldonic acids (see 2-Carb-20). 

The name of an aldose derivative in which the aldehyde group has been replaced by a terminal CH3 group is derived from that of the appropriate alditol (see 2-Carb-19) by use of the prefix deoxy- . 

The oxygen of ketone and aldehyde groups is readily replaced by halogen under the influence of phosphorus trichloride or pentachloride the reaction may be carried out with or without a solvent solvents commonly employed are chloroform, benzene, petroleum ether, acetyl chloride and phosphorus oxychloride. 

An aldehyde group can be replaced by a nitro group as shown by Salway [202] and Harding [202a] ... 

Systematic names for aldehydes are derived by replacing the final -e of the alkane name with -al. An aldehyde carbon is at the end of a chain, so it is number 1. If the aldehyde group is a substituent of a large unit (usually a ring), the suffix carbaldehyde is used. 

The third approach is useful when the spiropyran itself (or, more correctly, its intermediates) is easily available, the necessary substituted intermediates are not, and the spiropyran tolerates the chemical transformations involved. Halogenation and nitration of BIPS and spiro(dinaphthopyrans) can be carried out by standard methods bromo substituents replaced by cyano or lithium, nitro substituents reduced to amino, etc. For example, the aldehyde group in 6-formylBIPS can be reduced, oxidized, caused to react with organometallics, condensed with active methylene groups, converted to cyano, and derivatized to give a wide variety of 6-substituted BIPS. These reactions cannot be usefully carried out directly on 5-formylsalicylal-... 

The chlorophylls are tetrapyrrole pigments in which the porphyrin ring is in the dihydro form and the central metal atom is magnesium. There are two chlorophylls, a and b, which occur together in a ratio of about 1 25. Chlorophyll b differs from chlorophyll a in that the methyl group on carbon 3 is replaced with an aldehyde group. The structural for-... 

Protocol 3 is an example of an aza-Wittig reaction using l,2-bis(diphenyl-phosphino)ethane (DPPE or DIPHOS). The IMP is generated by reduction of the azide by DPPE, intramolecular reaction with the aldehyde group then occurs. It is worth noting the replacement of triphenylphosphine with DPPE. In the reaction... 

Vinylic chlorine is replaced by hydrogen in l-chloro-3,4-dihydro-2-naphthaldehyde during catalytic hydrogenation, which saturates the double bond, but leaves the aldehyde group intact (equation 9). ... 

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