Perfume Polarity

It would be very convenient if it were possible to calculate activity coefficients for any molecule in any given environment. Unfortunately, few situations occur in which this is possible, and rarely do such situations appertain to real products. Thus, for example, we may estimate the activity coefficients of many alkanes and simple derivatives at infinite dilution in water, but the corresponding values for the same materials in a specific shower gel are not readily calculable from first principles. However, a large number of parameters are available in the literature and have been used to answer questions related to physical behaviour. 

As a general guideline, the affinity between a molecule and its microenvironment will usually be higher when the molecule is surrounded by 

The pharmaceutical industry has for many years developed mathematical models to explain the biological activity of drugs these are termed as quantitative structure-activity relationships (QSARs). These techniques may also be applied to the situations described herein, although more correctly we are often more interested in QPARs, where the P stands for property (which may refer to macroscopic properties such as density, melting point or viscosity, or to molecular or sub-molecular 

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Although the behavior of the base perfume, and thus the odor value (OV) of each component, can be known, the OV in the new mixture will change because the OV depends largely on the solvent and the remaining aromatic components present in the perfume mixture. This is due to molecular size and in great extent to physical interactions at the molecular level, such as polarity forces (i.e. ion-dipole, dipole-dipole, hydrogen bonding forces, and others), in other words to the structure. 

It is useful to note that the retention times of materials determined by gas chromatography, using a carbowax-type polar column, give a fair indication of their relative volatilities within a compound. However, most perfumers develop their own way of thinking about volatility based on their personal experience and method of work. Too much of a scientific approach can be misleading, and the student perfumer will, in the words of Carles, "soon attain unexpected proficiency by forgetting any technical information he may have, and by establishing his classification for himself."... 

The nature of the perfume material. Molecules with a large molecular diameter diffuse far less rea< than smaller ones, and polar materials (with relatively high water solubility) less readily than nonpoh ones (compare Table 13.8). 

In perfumery practice solubility problems occur only at the extremes of the solvent range. At the high polarity end of the scale, the systems contain high proportions of water such as low-degree alcoholic skin lotions or after shaves, or foam baths and dishwashing liquids (surfactant-water blends) with very low surfactant levels. In the latter, salt is often added to increase viscosity. This addition further increases the polarity of the water and aggravates perfume solubility problems. 

Since perfume compositions normally are blends of perfume materials that differ widely in their polarity (even single essential oils represent such blends), the different components of a perfume are held back to differing degrees when the perfume is dissolved in a solvent. The patterns of differential holding vary greatly between different solvent systems. As a result, if a given perfume composition is dissolved in two different systems, the odor above the two will be distinctly different (Jellinek 1959). 

Association, due to polarization and hydrogen bonding, is of special significance to perfumers when it comes to the fixation of perfumes, and in the formulation of perfumes for such products as fabric detergents and conditioners where substantivity is a major requirement. The polar characteristics of perfumery materials are also of importance for their separation by gas chromatography when using certain types of column. 

We may conclude from the above that values of log P appear to give some guidance to the tendency of perfume ingredients to move from aqueous systems to (presumably) less polar surfaces (skin, hair, etc.). 

Ci2H10O, Mr 170.21, 6pi.7kPa 171-173 °C, df 1.171, ng° 1.6752, has been identified in some essential oils. It smells like orange blossom and is a colorless crystalline solid (mp 56 °C). It is usually prepared by Friedel-Crafts acetylation of naphthalene (with acetyl chloride, acetic anhydride, etc.) in the presence of aluminum chloride. In polar solvents (e.g., nitrobenzene), the percentage of the simultaneously formed a isomer is lower. Methyl P-naphthyl ketone is used in eau de cologne, soap perfumes, and detergents. It is a good fixative. 

The last ingredient, although seemingly innocuous, can cause major problems for the perfumer. In Chapter 7, the perfumer discussed the effect that the polarity, or relative water solubility of the perfumery... 

Uses Silylation reagent intermediate for silicone fluids chain terminating agent imparts water repellency as reagent for temporary protection of reactive sites in mfg. of betalactum antibiotics org. synthesis of carbohydrates, nucleosides, dyes, perfumes, agrochems. solubilizer in polar/nonpolar soivs. 

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