Aldehydes homologous series

CHO group attached to benzene ring, first member of aromatic aldehyde homologous series... 

The lower members of other homologous series of oxygen compounds— the acids, aldehydes, ketones, anhydrides, ethers and esters—have approximately the same limits of solubility as the alcohols and substitution and branching of the carbon chain has a similar influence. For the amines (primary, secondary and tertiary), the limit of solubility is about C whilst for the amides and nitriles it is about C4. 

Bruhl found that the increase of CHj in all the homologous series of fatty compounds corresponds to a difierence of 4 57 in the molecular refraction for the red hydrogen line. By deducting n times this value from the molecular refraction cf an aldehyde or ketone of the formula C H2 0, he found 2 328 to be the value for intra-radical oxygen. Similarly the values of other groupings have been determined which may be summarised as follows —... 

If a sample contains one or more members of a homologous series, identifications can be made using a plot of log tR against the number of carbon atoms, previously prepared from standards. The plot, which is valid for one temperature only, is linear and can be used for alkanes, alkenes, alcohols, aldehydes, ketones, esters and ethers. 

The effect of substituent groupings upon the first ionization potential of, at least, the aliphatic aldehydes and ketones does not seem to provide clear evidence for a choice between loss of a 7r-electron from the C=0 double bond or one of the oxygen lone-pair electrons. Concordant data for the homologous series of aliphatic ketones have been obtained by... 

The lower members of the homologous series of 1. Alcohols 2. Aldehydes 3. Ketones 4. Acids 5. Esters 6. Phenols 7. Anhydrides 8. Amines 9. Nitriles 10. Polyhydroxy phenols 1. Polybasic acids and hydro-oxy acids. 2. Glycols, poly-hydric alcohols, polyhydroxy aldehydes and ketones (sugars) 3. Some amides, ammo acids, di-and polyamino compounds, amino alcohols 4. Sulphonic acids 5. Sulphinic acids 6. Salts 1. Acids 2. Phenols 3. Imides 4. Some primary and secondary nitro compounds oximes 5. Mercaptans and thiophenols 6. Sulphonic acids, sulphinic acids, sulphuric acids, and sul-phonamides 7. Some diketones and (3-keto esters 1. Primary amines 2. Secondary aliphatic and aryl-alkyl amines 3. Aliphatic and some aryl-alkyl tertiary amines 4. Hydrazines 1. Unsaturated hydrocarbons 2. Some poly-alkylated aromatic hydrocarbons 3. Alcohols 4. Aldehydes 5. Ketones 6. Esters 7. Anhydrides 8. Ethers and acetals 9. Lactones 10. Acyl halides 1. Saturated aliphatic hydrocarbons Cyclic paraffin hydrocarbons 3. Aromatic hydrocarbons 4. Halogen derivatives of 1, 2 and 3 5. Diaryl ethers 1. Nitro compounds (tertiary) 2. Amides and derivatives of aldehydes and ketones 3. Nitriles 4. Negatively substituted amines 5. Nitroso, azo, hy-drazo, and other intermediate reduction products of nitro com-pounds 6. Sulphones, sul-phonamides of secondary amines, sulphides, sulphates and other Sulphur compounds... 

Bassette and Keeney (1960) ascribed the cereal-type flavor in dry skim milk to a homologous series of saturated aldehydes resulting from lipid oxidation in conjunction with products of the browning reaction. The results of Parks and Patton (1961) suggest that saturated and unsaturated aldehydes at levels near threshold may impart an off-flavor suggestive of staleness in dry whole milk. Wishner and Keeney (1963) concluded from studies on milk exposed to sunlight that C6 to Cn alk-2-enals are important contributors to the oxidized flavor in this product. Parks et al. (1963) concluded, as a result of quantitative carbonyl analysis and flavor studies, that alk-2-4-dienals, especially... 

In Figure 3, a straight-line relationship between a retention index and molecular weight is illustrated for homologous series of n-alcohols, n-aldehydes, n-acetates, and n-hydrocarbons. The compound having molecular weight 130 and retention index 1180 corresponds to n-pentyl acetate. Since the relationship in Figure 3 holds for all types of related compounds, it is obvious that this technique could be widely used in identification of GC peaks. 

The rabbit FruA discriminates the enantiomers of its natural substrate with a 20 1 preference for D-GA3P (12) over its L-antipode [202], Assistance from anionic binding was revealed by a study on a homologous series of carboxylated 2-hydroxyaldehydes which showed optimum enantioselectivity when the distance of the charged group equaled that of 12 (Scheme 15, Fig. 11) [299], The resolution of racemic substrates is not, however, generally useful since the kinetic enantioselectivity for nonionic aldehydes is rather low [202], 3-Azido substituents (69) can lead to an up to 9-fold preference of enantiomers in kinetically controlled experiments [300] while hydroxyl (70 preference for the... 

All the enthalpies of formation for acyclic aliphatic aldehydes and ketones which are discussed in this section are tabulated by Pedley and coworkers16. The number of these carbonyl compounds whose enthalpies of formation have been measured are few compared to the abundant data available for alkenes and so there are fewer decisions to make on which data to include. However, we then lack the means to make the comprehensive analyses we would prefer. The demonstrated linearity34 of the enthalpies of formation of the members of a homologous series vs the number of carbon atoms, nc, in the molecules provides an excellent visual method for determining the quality of the data any enthalpy of formation which deviates significantly from linearity is of questionable reliability. The linear relationship can be expressed as in equation 4 and the results of the regression analyses of this equation for aldehydes and ketones appear in Table 4. 

For homologous series of mono-functional alcohols, esters, aldehydes, ketones, acids, ethers, amides, nitriles and amines, the upper limit of water solubility is found at about the member containing four carbon atoms. The solubil-... 

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. 

Figure 6.5. Homologous series plots (a) linear (b) logarithmic. 1 = alkanes, 2 = cycloalkanes, 3 = esters, 4 = aldehydes, 5 = ketones, 6 = alcohols. Reprinted with permission from J. S. Lewis, H. W. Patton, and W. I. Kaye, Anal. Chem. 1956, 28, 1370. Copyright 1956, American Chemical Society.

Creamy flavors in butter have been associated with 4-cis heptenal produced for autoxidation of isolinoleic acid (Begeman and Koster, 1964). Drier flavor in foam spray-dried milk has been associated with 6-rra x-nonenal, which has a flavor threshold in fresh milk of 0.07 pg/kg (Parks et al., 1969). Bassette and Keeney (1960) implicated a homologous series of autoxidation-derived saturated aldehydes, together with products of Maillard browning, in cereal-type off-flavors in powdered skim milk. Staleness in dry whole milk may be associated with saturated and unsaturated aldehydes (Parks and Patton, 1961). 2,4-Decadienal has been reported to be the principal compound responsible for the off-flavor associated with spontaneously oxidized milk (Parks et al., 1963). Oxidized flavors in sunlight-exposed milk are commonly related to C6 to Cn alk-2-enals... 

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