Nomenclature of aldehydes

The positions of substituents on the chain may be indicated by the letters a, P, y, 8 in aldehydes beginning with the carbon atom closest to the aldehyde group. 

Because of the carbonyl group z=oj, aldehydes are polar molecules. 

Formaldehyde is a gas at room temperature. The C2 to C, j aldehydes are liquids and aldehydes higher than Cn are solids at room temperature. 

The carbonyl oxygen atom allows molecules of aldehydes to form strong hydrogen bonds with water molecules. As a result, low molar mass aldehydes show appreciable solubilities in water. As the molar mass increases, polarity decreases because of the effect of the hydrocarbon groups, hence the solubility in water also decreases. 

Low molar mass aldehydes dissolve in water due to hydrogen bonding. Hydrogen bonds are formed between the oxygen atom of the aldehyde and the hydrogen atom of water and also between the hydrogen atom of the aldehyde and the oxygen atom of water. 

---

Navarro-Avino, J. P, Prasad, R., Miralles, V. J., Benito, R. M., Serrano, R. (1999) A proposal for nomenclature of aldehyde dehydrogenases in Saccharomyces cerevisiae and characterization of the stress-inducible ALD2 and ALD5 genes. Yeast, 15, 829-842. 

IUPAC Nomenclature of Aldehydes Section ll.2A (a) decanal (b) 4-methylpentanal (c) 5-ethyl-3-methylheptanal ... 

Nomenclature of Aldehydes and Ketones.—The aldehydes are usually named from the acids into which they pass on oxidation, thus CH3.CHO is acetic aldehyde or acetaldehyde, as it is converted by oxidizing agents into acetic acid. In another system of nomenclature the name of an aldehyde is formed by adding the syllable al to the name of the hydrocarbon which contains the same number of carbon atoms as the aldehyde. According to this system acetaldehyde is called ethanal. 

Let s take a moment to review the nomenclature of aldehydes and ketones, before we look at their reactions. The suffix for the aldehyde group, CHO, is -al, and the carbonyl carbon atom is always numbered as C-1. The suffix for ketones is -one, and the chain is numbered so that the carbonyl group has the lowest number. So 14.1 is 5-chloro-4-ethyl-2-methyheptanal, and 14.2 is 4-chloro-6,8-dimethyl-3-nonanone. Remember that aldehydes and ketones are described as oxo substituents when there is an acid derivative in the molecule and that the acid derivative will take precedence in the numbering scheme. 

---