Odour similarity

Quinoline is a colourless liquid, having b.p. 236 and d, 1 095. It has an odour similar to, but fainter than, that of pyridine unlike pyridine, it is almost insoluble in water. 

Ethyl salicylate (prepared by the same method) has an odour similar to that of methyl salicylate but less intense it is therefore usually impracticable to attempt to distinguish methanol and ethanol by this test alone. 

Acetaldehyde, CH3CHO, b.p. 21°, is generally used in aqueous solution, which has also a characteristic odour paraldehyde, (CH3CHO)3, is a liquid polymer, b.p. 124°, slightly soluble in water, odour similar to that of acetaldehyde, but less intense. Chloral, CCI3CHO, a liquid, is almost invariably encountered as the stable solid hydrate , CCl3CH(OH)2, m.p. 57 . Both have a characteristic odour the hydrate is readily soluble in water. 

The solvent has a sweetish odour similar to chloroform detectable at about 30 ppm. It is primarily a depressant of tlie central nervous system (CNS). Significant impairment of performance in behavioural tests and some CNS effects have occuiTed at 1000 ppm but not at 300 ppm prenarcotic symptoms have occuired at mean levels of 200 ppm to 300 ppm. 

The colonrle.KS oil bad a peculiar odour, similar to that cf common heracleiiui oil. 

Homolinalyl Acetate.—This body has the constitution CjjHjgOOCCHj, and is prepared by the action of homolinalol-sodium on acetyl chloride, or by tbe action of acetic anhydride on homolinalol. It is an oil with a marked bergamot odour, similar to that of linalyl acetate, but not identical with it. It boils at 111° to 117° at 15 mm. 

Halothane was introduced into clinical practice in 1956. It was not the first fluorinated anaesthetic— fluoroxene (Fluoromar) holds that distinction—but it was the first to achieve widespread acceptability. Halothane is a fluorinated alkane 1-bromo, 1-chloro -2,2,2-trifluoroethane (Figure 3.2). It has a characteristic odour, similar to chloroform, and requires a stabiliser, thymol (0.01%), to prevent degradation by light. Halothane has a blood/gas partition coefficient of 2.4 able 3.2) but its lack of irritant qualities makes possible the use of relatively high inspired concentrations (2-4%). For that reason, inhalation induction is characteristically smooth and rapid. Compared to sevoflurane, and possibly isoflurane, recovery from halothane anaesthesia is delayed. 

This section reviews the molecular shape descriptors developed by Amoore, Allinger, Simon et al. and Testa and Purcell. The illustrative examples discussed refer to the odour similarity and cardiotoxic aglycones. One has stressed the methods based on the reference structure because, correctly formulated, these methods seem to offer promising perspectives to model the steric effects in biological systems. Finally, a short discussion of possible connections between steric and other substituent constants (relevant in the context of multicollinearity in QSAR) is included. 

Recently, Motoc et al. have studied9 the correlational ability of Amoore s parameter, the stability and predictive value of the resulted equations (the odour similarity, Y, and the corresponding AN values were taken from ref.10)). The model ... 

Y, stand for the odour similarity i = 1-ethereal, 2-camphoraceous, 3-musky, 4-floral, 5-minty)... 

The correlations which emerge are modest. They may be justified by the imprecision of experimental data (these data may be poor because odour similarity is obtained as average from a jury of 29 persons), or/and by the ad-hoc criterion used to perform the geometrical congruence. 

Carvone (94) occurs as (+)-carvone, (-)-carvone or racemic carvone. (S)-(+)-Carvone is the main component of caraway oil (ca 60%) and dill oil and has a herbaceous odour reminiscent of caraway and dill seeds. (R)-(-)-Carvone occurs in spearmint oil at a concentration of 70-80% and has a herbaceous odour similar to spearmint [26]. (S)-(+)-Carvone (94) was used as substrate for bioconversions by selected microorganisms five... 

Bergstrom, G. and Lofqvist, J. (1968). Odour similarities between the slave-keeping ants... 

Examples of essential oil compounds showing these different odours include d-limonene, which has a dull citrus odour while /-limonene has a turpentine odour similarly, d-linalool has a floral, woody (lavender-like) odour, while /-linalool has a floral (petitgrain-like) odour. 

These three chloro-derivatives are obtained as colourless liquids which become faintly green on exposure to daylight. They have odours similar to that of dichloroethyl sulphide, but have no vesicant properties, while their melting points are much lower. 

Carbonyl dibromide is a dense, colourless, mobile liquid, fuming in moist air due to hydrolysis, with an odour similar to that of phosgene [2126]. Its relative molecular mass is 187.8184. It is much less stable to dissociation than phosgene even distillation at atmospheric pressure results In a slight yellow colouration due to liberated bromine. 

Under normal conditions of temperature and pressure, COCIF is a gas. It is colourless in both the gaseous and condensed states, and has an odour similar to, but distinguishable from, phosgene. It is non-flammable. 

COBrF is described [1751] as having an odour similar to that of phosgene, and... 

Only a few of the physical properties of COBrF have been measured. Carbonyl bromide fluoride (relative molecular mass 126.91) is a colourless gas, with an odour similar to, but distinguishable from, phosgene [1195]. The melting point at atmospheric pressure of COBrF has been reported as -120 2 C [1196a], and the boiling point as -20.6 "C [1196a]. Its critical temperature occurs at +124 C, and its critical pressure is ca. 6.18 MPa [656a,1751]. 

As odour similarity ratings, where the odour quality of one odour type is rated against that of a standard. For example, if a scale of 0 to 10 is used, a compound which is identical in odour to the standard is given a score of 10 and one which is completely different a score of 0. 

The last was used by Boelens and Punter (1978) to quantify the odour quality of 16 muguet-smelling materials. These data were then used to derive equation (3), which related the odour similarity (OS) to molecular weight (MW) and the Kier connectivity index (A ). The concept of molecular connectivity was introduced by Randic (1975) and further elaborated by Kier and Hall (1976). It involves the calculation of numerical indices which describe the topology of a molecule. The Kier... 

Boelens has also used this approach to derive QSAR equations for musk, jasmine, fruit and bitter almond odorants (Boelens, 1976 Boelens and Punter, 1978 Boelens et al., 1983). In the case of bitter almond and musk, he concluded that hydrophobic and steric parameters were important. For the jasmine materials, he found that molecular connectivity indices were useful parameters. Molecular connectivity indices were also used by their inventors, Kier et al. (1977), to analyse anosmia to fatty acids and the odour similarities of ethereal, floral and benzaldehyde-like odorants. Dearden (1994) also developed a QSAR equation relating the odour similarity of bitter almond odorants to two connectivity indices. Greenberg (1979) found that the odour intensity of a series of homologous compounds was correlated to their hydrophobic properties and not to steric or polar properties, while Rossiter (1996b) found that the fruitiness of aliphatic esters was related to steric hindrance of the ester group and either molecular length or log P. 

Undecenoates are mixtures of similar fatty acids with antifungal activity. Preparations should be protected from light as this denatures them. They have a peculiar odour (similar to sweat) that is difficult to mask. Preparations of undecenoates are available as over-the-counter medicines, for example Mycota. 

I Thiolane is a colourless, water-insoluble liquid of bp 121°C. It has a distinctive odour similar to town gas. In combination with other compounds, it is responsible for the typical odour of... 

Dichloro ethane 50 Colourless oily liquid having odour similar to chloroform bp 83°C. Slightly water soluble and flammable. Causes irritation of respiratory tract, weakness, anxiety, headache and convulsions. To be handled in a well-ventilated area. 

A phenolic odour, similar to that of antiseptic soap indicates the presence of Bakelite (Parry, 1996). A fishy odour is often produced by warming melamine-or urea-formaldehydes. Unfortunately, description of odour is very subjective and it is difficult for testers to agree (Table 5.2). Although the odour of warm... 

Methanol, or as it is termed in full methyl alcohol, with the chemical formula CH3OH is the first of the long series of alcohols. Its molecular weight is 32.04 and it is a neutral, colourless liquid in pure condition having an odour similar to that of ethyl alcohol. Methanol dissolves well with other alcohols, esters, ketones as well as with aromatic hydrocarbons and water. It can be less well mixed with fats and oils. It dissolves a number of organic substances including numerous salts. The most important physical data for methanol are assembled in Tables 3.1 to 3.5. Further data on the physical properties of methanol can be taken from the literature under [3.3-to 3.10]. 

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