Functional group aldehyde

The common method of naming aldehydes corresponds very closely to that of the related acids (see Carboxylic acids), in that the term aldehyde is added to the base name of the acid. For example, formaldehyde (qv) comes from formic acid, acetaldehyde (qv) from acetic acid, and butyraldehyde (qv) from butyric acid. If the compound contains more than two aldehyde groups, or is cycHc, the name is formed using carbaldehyde to indicate the functionaUty. The lUPAC system of aldehyde nomenclature drops the final e from the name of the parent acycHc hydrocarbon and adds al If two aldehyde functional groups are present, the suffix -dialis used. The prefix formjlis used with polyfunctional compounds. Examples of nomenclature types are shown in Table 1. 

Aldose (Section 25.1) A carbohydrate with an aldehyde functional group. 

Do you expect the aldehyde functional group (CHO) to act as a meta-directing or as an ortho, para-directing group Explain. 

Herner HA, JE Trosko, SJ Masten (2001) The epigenic toxicity of pyrene and related ozonation byproducts containing an aldehyde functional group. Environ Sci Technol 35 3576-3583. 

The aldehydes are a group of compounds with the general formula R-CHO. The aldehyde functional group is always written -CHO, even though this does not represent the aldehyde s structural formula. It is written in this way so that the aldehydes will not be confused with R-OH, the general formula of the alcohols. 

The first synthesis of peptide aldehydes involved amino acid residues with no side-chain functional groups. Subsequently, peptide aldehydes with a number of side-chain functional groups have been synthesized. Protecting groups utilized include Arg(N02), Lys(Z), Asp(OCy), Asp(OtBu), Glu(OtBu), Ser(Z), Thr(tBu), and Cys(Z). 311 1319 20 It should be noted that many unprotected side-chain functional groups will react with the aldehyde functional group and this is discussed in Section 15.1.1.1. 3,5,11,21 ... 

Protection of peptide aldehydes as semicarbazones serves two purposes (1) it reduces or eliminates racemization during chromatographic separation, and (2) the semicarbazone protects the aldehyde functional group during subsequent peptide coupling reactions. Crude aldehydes can be immediately reacted with semicarbazide hydrochloride to give the corresponding semicarbazones. The semicarbazones are purified on a silica gel column and are subsequently deprotected with 37% formaldehyde/HCl. To determine the optical purity, the aldehydes are immediately reduced with sodium borohydride followed by determination of the optical rotation of the alcohol (Table 3).[5]... 

The stereochemistry of the Weinreb-based and phenyl ester based technique has been determined through studying the epimerization of the carbon located a to the aldehyde functional group.135 4 50 Crude products such as Boc-Phe-Val-Ala-H synthesized by both methods contain only one aldehydic peak meaning these techniques are devoid of racemi-zation. However, when the crude products were separated using flash chromatography with 0.1% pyridine as eluant, two aldehydic peaks appeared, which is indicative of some race-mization during separation. 55 4 511 ... 

The aldehyde functional group is a very reactive functional group thus methods to prepare it must be mild and allow the aldehyde group to survive the reaction conditions. Traditional methods for introduction of the aldehyde functional group include... 

Aldehydes are intermediate ill oxidation level, and thus the aldehyde functional group can be installed by either reduction of carboxylic acid derivatives or oxidation of alcohols. Aldehydes are rarely installed without a change of oxidation level. One difficulty is that they undergo both oxidation and reduction readily. Special methods are required to stop at the aldehyde stage rather than proceeding by further reduction or oxidation. 

Glucose contains five hydroxyl groups and an aldehyde functional group. Its hydrogenation will not affect the hydroxyl groups but will reduce the aldehyde to a primary alcohol. 

Figure 12.8 shows structures and names of the D-aldohexoses. These compounds all have six carbon atoms, have an aldehyde functional group, and have the OH group on C5 pointed to the right. Of these eight compounds, glucose is by far the most common. 

Numerous additional tests to determine the effect of the carbon chain on the functional group were conducted using a homologous series. The effect of unsaturation is pronounced only in cases where the double bond is conjugated with the aldehydic functional group. For example, trans-2-hexenal ( ) had a AT value of 1.50 as compared to n-hexanal with a value of 0.93. The ease of electron delocalization in trans-2-hexenal, as shown below, increases the polarity of the molecule, hence its higher AT value. 

Hydrogen gas is dissociatively chemisorbed onto the surface of the Cu-containing catalyst producing highly active hydrogen atoms. The high pressure is needed to ensure adequate solubility of the H2 in the furfural liquid. The aldehyde functional group forms a weak bond... 

The carboxylic acid and aldehyde functional groups are located at an end of the molecule, whereas ketones and esters have their functional group located in the interior of the molecules. 

Only two ozonolysis products contain aldehyde functional groups these fragments must have been double-bonded to each other in erythrogenic acid. 

Ribitol is an optically inactive meso compound. Catalytic hydrogenation converts the aldehyde functional group into a hydroxyl group and makes the two halves of ribitol images of each other. 

In general, ketones are less reactive than aldehydes for both steric (excess crowding) and electronic reasons. If the keto aldehyde in this problem were reduced with one equivalent of NaBJLj, the aldehyde functional group would be reduced in preference to the ketone. 

For the same reason, reaction of the keto aldehyde with one equivalent of ethylene glycol selectively forms the acetal of the aldehyde functional group. The ketone can then be reduced with NaBFLj and the acetal protecting group can be removed. 

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