The replacement of synthetic conventional compounds by natural ingredients; whether in medicine, food, or cosmetics; has been increasingly requested by consumers, especially since the last decade. Terpenes in general and monoterpenes in particular are secondary metabolites in plants, and they may be a promising natural alternative. Monoterpenes, the main constituents of plants’ essential oils, are odorous compounds that play a significant ecological role in plant evolution. They are primarily utilized by the flavour and fragrance industries due to their characteristic aroma. In addition, a series of representatives belonging to this substance class are antimicrobial, anti-inflammatory, antiseptic, and anticancer agents; or elicit other therapeutic effects. Thereby, acyclic monoterpene alcohols, mainly linalool, geraniol, nerol, and citronellol, are primarily in the focus of scientific research. Besides their aromatic character and their role in aromatherapy, they induce a series of pharmacological and physiological effects. In view of the latter, their metabolic pathways have been previously investigated in both plants and animals. Linalool and geraniol, for example, are metabolized giving 8-hydroxy and 8-carboxy derivatives; i.e. undergoing oxidation at C-8. However, these metabolites have not been tested in terms of odour or other physiological activities. Furthermore, no studies are at hand elucidating which structural features of these substances are responsible for specific odour qualities and potencies of these monoterpenes. In the frame of this doctoral thesis, a comparison between chemical structure and odour character of selected monoterpenes relating to linalool, geraniol, nerol, and β- citronellol has been conducted, complemented by investigations on their acetate derivatives and previously identified oxygenated metabolites. To achieve this aim, a series of oxygenated derivatives, bearing an aldehyde, an alcohol, or an acid functional group at C-8, were synthesized from the aforementioned terpene alcohols and acetates yielding 24 compounds, yielding a comprehensive substance library for future elucidation of the substances’ presence in nature and evaluation of their further potential physiological properties. Within this study, however, the focus lies on a comprehensive characterization of the compounds’ olfactory properties. Accordingly, all compounds were tested in relation to their odour qualities and relative odour thresholds (OTs) in air, as well as potential inter-individual variations in sensory perception for each single substance. Overall, the results show that v almost all investigated parent monoterpene alcohols and their acetates exhibited closely related odour characters; ranging between citrus-like, fresh, fruity, floral-sweet, and fatty. Amongst others, linalool was demonstrated to be the most potent monoterpene of the group of investigated compounds, eliciting an OT of 3.2 ng/Lair. According to this study, the presence of an OH group at C-3 in the linalool basic structure is the main contributor to its characteristic odour quality and high potency. On the other hand, the occurrence of this OH at C-1 in geraniol, nerol, and citronellol does not alter their odour quality but increases their odour threshold levels, with values of 40, 60 and 10 ng/Lair, respectively. Esterification of this OH-group to the respective acetate barely affected the odour quality, but provoked a decline in odour potency. Substitution at C-8 of either the parent monoterpeneols or their acetates by another OH-group retained the smell of the parent compounds but led to a dramatic decrease in the potency. However, the smell potency was only retained when replacing the alcoholic group at C-8 by an aldehyde or an acid group. It is worth mentioning that among the acetate derivatives 8-oxolinalyl acetate elicits similar smell impressions as linalool, thus exhibiting a citrus-like, fresh odour with an OT of 5.9 ng/Lair. Apart from that, further oxidation of C-8 of linalool, geraniol, citronellol, and citronellyl acetate to their corresponding acids led to a total odour loss.