Fragrant compounds

Chemistry of fragrant compounds (lactones and other 0-heterocycles) 98T7633. 

Myristicin, CjjHjgOg, is 4-allyl-6-methoxy-l. 2-methylenedioxybenzene. It is found in oil of nutmeg and in parsley oil. It is a fragrant compound having the following characters —... 

SELF-TEST 8.14B When 200. mg of linalool, a fragrant compound found in cinnamon oil from Sri Lanka, was added to 100. g of camphor, it lowered the freezing point of camphor by 0.51°C. What is the molar mass of linalool ... 

Trees and shrubs contain a group of fragrant compounds called terpenes. The simplest terpene is isoprene. All other terpenes are built around carbon skeletons constructed from one or more isoprene units. Plants emit terpenes into the atmosphere, as anyone who has walked in a pine or eucalyptus forest will have noticed. The possible effect of terpenes on the concentration of ozone in the troposphere has been the subject of much debate and has led to careful measurements of rates of reaction with ozone. 

The telomer of nitromethane with four moles of butadiene 62 has a chain of 17 carbons, and this compound is a very suitable starting material with right carbon numbers and necessary functionalities for the synthesis of civetone (133), a naturally occurring fragrant compound. The telomer was converted into civetonedicarboxylic acid (132) by the following sequence of reactions ... 

The intensity of a fragrant compound i can be expressed in terms of its odor value, OVj, which is defined as ... 

Essential oils are organic compounds derived from flowers, seeds, leaves, roots, resins, and citrus fruits. The structures of many fragrant compounds have been studied, and processes for making these valuable compounds in a laboratory have been developed. There are now approximately 5000 synthetically produced chemicals that are available to a perfumer. These chemicals include vanillin, rose oxides, and the damascenes, or rose ketones. 

Allylic amines are difficult to cleave, but they can be cleaved by using a cationic Pd complex and DPPB as a ligand. As an example, N, /V-dicthylgcranylamine (348) is converted 349, and its regioselective dehydropalladation affords the myrcene-type conjugated diene 350, and the reaction is applied to commercial production of the fragrant compound 351, called kovanol [166]. 1,4-Elimination of allylic amines is also possible as their amine salts using AcOH as a solvent [167],... 

This delocalized ring structure is called aromatic. Structures possessing this feature are frequently associated with substances with distinct aromas and the concept of aromaticity derives from this fact. While in colloquial terms aromatic is commonly applied to describe strongly fragrant compounds, in chemical technical terminology it refers purely to the possession of this type... 

Originally the word aromatic was applied to pleasant-smelling substances. The word now describes benzene, its derivatives, and certain other compounds that exhibit similar chemical properties. Some have very foul odors because of substituents on the benzene ring. On the other hand, many fragrant compounds do not contain benzene rings. 

Steam distillation is the main commercial extraction procedure for the production of essential oils from almost any type of plant material. Solvent extraction is also used commercially and yields a resinoid, concrete or absolute according to the solvents and techniques used (see Chapter 4). Both steam distillation and solvent extraction are used on a laboratory scale to produce oils and extracts for analysis. Other methods of extraction, such as supercritical fluid extraction (SFE), which uses supercritical CO2 as the extraction solvent, are now being developed and used on both commercial and laboratory scales. The extracts produced by SFE may contain different materials from the steam-distilled oil because of the solvating power of C02 and the lower extraction temperature, which reduces thermal degradation. The C02 extract may therefore have an odour closer to that of the original material and may contain different fragrant compounds. The choice of extraction procedure depends on the nature and amount of material available, and the qualities desired in the extract. Solvent extraction is better suited to small sample amounts or volatile materi-... 

The term aromatic acknowledges the fact that many fragrant compounds contain benzene rings, whilst the term aliphatic is derived from the Greek word for fat or oil. 

Aromatics Originally meaning fragrant compounds, aromatics are now defined as Benzenes and those compounds which resemble benzene in their chemical behaviour . Simple aromatics contain only one aromatic ring and may be either mono-, di- or tri-substituted, for example, one, two or three hydrogen atoms in benzene can be substituted to form methyl benzene (toluene), dimethyl benzene (xylene) and trimethyl benzene respectively as in Figure 6.2. Aromatic... 

Organic chemistry has two main divisions. One division deals with ali-phatic (fatty) compounds, the first compounds you encountered in Organic Chemistry I. Methane is a typical example of this type of compound. The second division includes the aromatic (fragrant) compounds, of which benzene is a typical example. 

The synthesis of tocopherol and related compounds has been reviewed. The conformations of coumarins which have anticoagulant action on blood have been studied crystallographically. A valuable review of the occurrence and distribution of the 462 flavonoids that had been found in plants up to the time of its writing was published in 1981. The use of 4-phenyl-l,3-dioxan as an intermediate in the synthesis of fragrant compounds has been surveyed. Chlorinated dibenzodioxins are important compounds, and the first part of a timely review of the thermal formation of these compounds has appeared. All chemists who are active in the benzopyrone field will be saddened to know of the death of Professor K. Venkataraman his life and work is summarized in an appreciation. ... 

Many extracts are based chemically on the benzene ring, a class of often fragrant compounds which have come to be called aromatics as a consequence. They include benzaldehyde, which smells like almonds, and vanillin, the basis of vanilla. Camphor oil (8008-51-3) is the essential oil removed from the camphor tree. It contains camphor, as well as many other compounds. Camphor may also be extracted from other natural sources, but usually in smaller quantities. Vegetable extracts usually contain terpenes (CjoHig), a class of flammable hydrocarbons based on the isoprene unit (C5H8). 

When allylic alcohols are used as an alkene component in HR, elimination occurs from an oxygen-bearing carbon, and aldehydes or ketones are obtained, rather than jS-arylated allylic alcohols [68,69]. The reaction of methallyl alcohol (113) with a halobenzene is a good synthetic method for dihydro-2-methylcinnamaldehyde, an important fragrant compound 114. The allylic alcohol 115 is not formed. An intramolecular version of the aldehyde formation was applied to the preparation of the key intermediate 117 from 116 in the total synthesis of saponaceolide [70]. 

Chemists also learned that the term aromatic was not always accurate. Many compounds that belong to the class because of chemical properties and structures are not at all fragrant. Conversely, there are many fragrant compounds that do not have aromatic compound properties or structures. Today, the old class name is used but with a different meaning. Aromatic compounds are those that contain the characteristic benzene ring or... 

Acyclic diterpenes are not common. Most known acyclic diterpenes are derived from hydrolysis of GGPP and relatively simple modifications (Figs. 22.3 and 22.4). The fragrant compound geranylgeraniol (3) is accumulated in the wood of Cedrela toona (Meliaceae) (Croteau and Johnson, 1985). The monounsaturated diterpene, phytol (4), is a com-... 

Myrcene, a fragrant compound found in bayberry wax, has the formula C oHie and is known not to contain any triple bonds. 

Linalool, a fragrant compound that can be isolated from a variety of plants, is 3,7-dimethyl-l,6-octadien-3 ol. Linalool is used in making perfumes, and it can be synthesized in the following way ... 

PROBLEM 19.85 Reaction of salicylaldehyde (1) and acetic anhydride in the presence of sodium acetate gives compound 2, a fragrant compound occurring in sweet clover. 

Most perfumes are a 10-25% solution of the fragrant compounds in alcohol. Colognes are usually diluted versions with only 0.5-2% fragrant compounds. 

Several typical examples of naturally occurring fragrant compounds, that is, synthesized by plants and flowers and other living organisms, are shown in Fig. 12.1. Geraniol-nerol and citronellol (and their derivatives) are responsible for the rosy floral scents. Linalool causes the floral scent of lavender and bergamot. Linalyl acetate gives fruity odor. Methyl ionone is found in iris-violet. Menthol may be familiar to you the odor of mint comes from it. Pine scent is caused by terpineol, bomeol, and their derivatives. 

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