Favored Conformations of Carbonyl Compounds: A Structural Study of n‐Octanal

Abstract

We report on the molecular structures of the two most abundant conformers of n-octanal observed by molecular beam Fourier transform microwave spectroscopy. Next to limonene, which is the main component of citrus-oil, octanal and other n-alkyl aldehydes strongly enhance the typical fresh smell of lemon-oil. Due to the high flexibility of its n-alkyl chain and the high number of possible conformers, different semi-empirical methods (AM1, PM3, MMFF94) were used to sample the conformational space of octanal before performing more sophisticated quantum chemical calculations at the MP2 level of theory. This technique has previously been shown to be an ideal tool to characterize relevant odorant structures in fragrance chemistry. The structure of octanal and structurally related molecules is discussed in the context of the most abundant chain conformations and the potential use of the microwave validated structures for further studies in biological media.

Internal Rotation of the Acetyl Methyl Group in Methyl Alkyl Ketones: The Microwave Spectrum of Octan‐2‐one

“…"Chemical intuition" would suggest a preference for the C s structure. However, similar bent configurations have been observed for a number of molecules where an alkyl chain is attached to a carbonyl group such as n-aldehydes [40][41][42][43] and esters like ethyl valerate. [44] In a study on methyl butyrate, Hernandez-Castillo et al determined a population ratio of 59/41 for the (g � ,a) conformer (C 1 conformer equivalent) vs. the (a,a) conformer (C s conformer equivalent).…”

“…“Chemical intuition” would suggest a preference for the C s structure. However, similar bent configurations have been observed for a number of molecules where an alkyl chain is attached to a carbonyl group such as n ‐aldehydes and esters like ethyl valerate . In a study on methyl butyrate, Hernandez‐Castillo et al.…”

α‐Dioxygenases (α‐DOXs): Promising Biocatalysts for the Environmentally Friendly Production of Aroma Compounds

“…[1a] Consequently, various aliphatic aldehydes are formulated in the mixture of many renowned perfumes. [3] Unsaturated aldehydes like (E)-2-hexenal and (Z)-11-hexadecanal are produced by insects and are good candidates for pheromone synthesis. [4] In addition, methyl-branched aldehydes (e. g., 12-methyltridecanal) are used as food supplements, adding a meaty flavor.…”

“…Aliphatic fatty aldehydes (FALs), typically derived from fatty acids (FAs), possess structural diversity depending on the carbon chain length and the existence/number/position of double bonds or other substituents, which translates into different physicochemical properties [2] . FALs have a high commercial value as fragrances and flavor agents with a market‐value of 35 billion USD [3] . The medium‐chained octanal, nonanal, and decanal are noted as green‐floral and citrus flavors, and considered as suitable scents in perfumes [1a] .…”

Process for the Preparation of Fatty Aldehydes from Renewable Resources

“…Dodecanoate is a component found in high concentrations in plants such as Laurus nobilis (Laurel), while dodecylaldehyd is a flavoring agent and fragrance used in industrial products such as perfumes – a prominent example being Chanel No.5 , . The introduced process consists of three main steps that are shown in Fig.…”