Geraniol smell

C10H13O. B.p. 225-226"C. A terpenic alcohol and a constituent of neroli, petit-grain and bergamot, and of many other essential oils. Nerol has a blander smell than its isomer, geraniol, and is more valuable as a constituent of perfumes. 

Esters derived from the weakly smelling benzyl alcohol are much less closely related to each other than those derived from more powerful alcohols such as linalool, geraniol, paracresol, or even phenylethyl alcohol. The higher esters of benzyl alcohol, in particular, seem to owe little to the character of the alcohol. 

Monoterpenes are important constituents of essential oils. These complex mixtures of compounds, as well as individual monoterpenes are used in medicine (F 2) and industry (F 4). Commercially important monoterpenes are, for instance, menthol, camphor, carvone, thymol, fenchone, and oc-pinene. Monoterpenes flavor foodstuffs and beverages (F 1). Citral, for example, is an important constituent of the smell of lemon. Thymol is involved in the flavor of mandarin oranges. Other monoterpenes, e.g., limonene and geraniol, are constituents of flower scents and attract plant pollinators (E 5.5.1). High monoterpene concentrations in plants will repel most potential predators, but my attract some animals (E 5.5.3). Animals use citronellal, citral, and oc- and jS-pinene als feeding deterrents (E 5.1) and geraniol, geranyl esters, myrcene, and terpinolene as pheromones (E 4). Some monoterpenes, e.g., 1,8-cineole and camphor, are also involved in plant-plant interactions (E 5.3). 

If we walk into a blooming rose garden, however, we immediately notice something different when we inhale—a pleasant smell. What causes it The molecules in the rose garden are not much different than those in ordinary air-20% oxygen and 80% nitrogen. However, there is a small difference-about 1 molecule in every 100 million is geraniol or 2-phenylethanol, the molecules responsible for the smell of roses. 

When people smell a rose, they inhale molecules of a compound called geraniol. These molecules trigger nerve signals that our brain interprets as a sweet smell. 

Hydrolysis of geranyl diphosphate gives geraniol, a pleasant-smelling monoterpene found in rose oil. 

The primary aromatic substances in beer are derived from raw materials (barley or hops) that confer the beer s typical odour and taste. Bitter acids of hops have a bitter taste (see Section 8.3.5.1.3), but hop cones also contain 0.3-1% m/m of terpenoids (60-80% of hop essential oil), which have a considerable influence on the smell of beer. The main components of aromatic hop oils are sesquiterpenic hydrocarbons in which a-humulene, P-caryophyllene and famesene dominate. The major monoter-penic hydrocarbon is myrcene. For example, the essential oil content of fine aromatic varieties, such as Saaz, is 0.8% m/m, of which 23% is myrcene, 20.5% a-humulene, 14% famesene 6% and P-caryophyUene. Significant components of the hop aroma in beer are mainly isomeric terpenoid monoepoxides resulting from autoxidation and diepoxides of a-humulene and fS-caryophyUene, but also other terpenoids. Important components of hops odour are also various alcohols (such as geraniol and hnalool), esters (ethyl 2-methylpropanoate, methyl 2-methylbutanoate, propyl 2-methylbutanoate and esters of terpenic alcohols, such as geranyl isobutanoate), hydrocarbons, aldehydes and ketones formed by oxidation of fatty acids, such as (3E,5Z)-undeca-l,3,5-triene, (Z)-hex-3-enal, nonanal, (Z)-octa-l,5-dien-3-one, their epoxides, such as ( )-4,5-epoxydec-2-enal and sulfur compounds. Other important components of hops are so-called polyphenols (condensed tannins) that influence the beer s taste and have antioxidant effects. Less important compounds are waxes and other hpids. Hop products, such as powder, pellets and extracts (by extraction with carbon... 

One important point on smell is that just as with taste molecules of different structures, often totally different molecules, have the same or different smell. An example of rose odor in reference (1.) sites the work of Wright (12) where rosetone, phenylethanol, geraniol and pelargol are compounds with very different structures but the same smell. He also attributes camphor smell to camphor, chloroethane and ethyl-tert-butyl ether (12). Other research of this type would be odorant molecules of similar structure with a different olfactory response. In 1929 Braun (13) studied a series of ketones where the carbonyl moved from carbon two through carbon six of an eleven carbon ketone. 

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