Base notes

Figure 4.12 Standard bulk meter layout for a brick-built chamber (230 mm brickwork on a concrete base). Notes (1) the flowmeter should be either on straight or bypass to suit specific site (i.e. to keep meter off road). (2) Chamber cover should be approximately 685 mm x 510 mm...

The following list divides types of unsafe acts into those that are skill-hased, perceptual, and decision or knowledge-based. (Note that this division is different from the skills-rules-model knowledge-based model described earlier.) Examples are given of each type of error that may result in an unsafe act.( )... 

The alkane propane has pATa 50, yet the presence of the double bond in propene means the methyl protons in this alkene have pATa 43 this value is similar to that of ethylene (pATa 44), where increased acidity was rationalized through sp hybridization effects. 1,3-Pentadiene is yet more acidic, having pATa 33 for the methyl protons. In each case, increased acidity in the unsaturated compounds may be ascribed to delocalization of charge in the conjugate base. Note that we use the term allyl for the propenyl group. 

This means that a reverse Claisen reaction can occur if a P-ketoester is treated with base. This is most likely to occur if we attempt to hydrolyse the P-ketoester to give a P-ketoacid using aqueous base. Note that the alcoholic base used for the Claisen reaction does not affect the ester group. 

At every stage of the development process, the results of a reaction or process stage will be analysed in one of two ways. The reaction mixture itself will be sampled and analysed to yield information such as extent/completion of reaction, reaction yield or reaction purity. Alternatively, the reaction product will be isolated and dried before sampling and analysis. Typical analytical information in this case would include both chemical and physical characterisation, plus quantitative data to ensure conformance with some pre-defined specification or to provide batch data on which a suitable specification will ultimately be based. Note that however quickly the analytical data are provided, there is a disconnect from the reaction, which means that reaction control is impossible and that... 

Peruse Table 16-1 for a list of common acids and bases, noting that all the acids in the list contain a hydrogen at the beginnings of their formulas and that most of the bases contain a hydroxide. The Arrhenius definition of acids and bases is straightforward and works for many common acids and bases, but it s limited by its narrow definition of bases. 

Nerolidol is used as a base note in many delicate flowery odor complexes. It is also an intermediate in the production of vitamins E and Ki. 

The extracts and absolutes are used in perfumery for nuances and as a fixative to give compositions a dry, sweet base note, e.g, in fougere and chypre perfumes. Occasionally occuring allergenic responses to oakmoss and treemoss products are... 

A. O-Diphenylphosphinylhydi oxylamine. A 5ilO-mL, round-bottomed flask, equipped with a reflux condenser, drying tube, an efficient mechanical stirrer, a dropping funnel and a nitrogen-inlet tube, 1s charged with 300 mL of anhydrous methylene chloride, 16.5 g (0.5 mol) of hydroxylamine base (Note 1), and 1,0 g of dry sodium bicarbonate. While the suspension 1s stirred vigorously at -30°C (bath temperature), a solution of 52.06 g (0.22 mol) of diphenylphosphinyl chloride (Note 2) in 70 mL of anhydrous methylene chloride... 

In this, as in many other cases in aqueous solution, OH" plays the role of the base. Note that for compounds such as 1,1,2,2-tetrachloroethane and pentachloroethane, the base catalyzed reaction is important at quite low pH values (/NB = 4.5, i.e., pH at which the neutral and base catalyzed reaction are equally important, see Table 13.7 and Section 13.3). In fact, for polyhalogenated alkanes a small7NB value (e.g., <7) is indicative of an E2 reaction, or, in special cases, of an E1CB reaction see below. Some other examples of compounds reacting by an E2-mechanism include 1,1,2-trichloro-ethane, 1,1,2-tribromoethane, and l,2-dibromo-3-chloroethane (see Table 13.7). A high /NB value (e.g., >10) does not, however, necessarily exclude ( elimination, because this reaction may also occur with water as base, or by an alternative to the SN1 mechanism (i.e., an El mechanism, see below). 

Arrows indicate the phosphodiester bonds cleaved by each restriction endonuclease, Asterisks indicate bases that are methylated by the corresponding methylase (where known), N denotes any base. Note that the name of each enzyme consists of a three-letter abbreviation (in italics) of the bacterial species from which it is derived, sometimes followed by a strain designation and Roman numerals to distinguish different restriction endonucleases isolated from the same bacterial species, Thus BamHI is the first (I) restriction endonuclease characterized from Bacillus amyloliquefaciens, strain H. 

Fig. 7. Comparison of the pH-dependence of cholinesterase inhibition by eserine with the titration curve of the base. (Note, that inhibition does not disappear when the percentage of cationic form in solution approaches zero. This may be interpreted in two ways (a) either the free base as such possesses a certain inhibitory power or (6) the dissociation constant, measured in aqueous solution, is not identical with...

Additional base notes Diphenyl oxide Cassione Frambinone Musk T Ambrettolide... 

Examining the structure of a perfume in more detail, we may conveniently consider the main components under three separate headings the perfumery accord the relation between top, middle, and base notes and the balance between simplicity and complexity. 

Perfumery materials differ widely in their volatility, from those that last only a few minutes on a smelling strip to those that are still there after several weeks. It is usual therefore (Poucher 1955 Carles 1961) to divide materials into three groups the base notes which are the most long lasting the middle notes, or modifiers, which are of medium volatility and the top notes which are the most volatile. The balance between these three groups of materials in a formula is of great importance to the way in which the perfume diffuses during its evaporation and to its aesthetic quality. 

Diagrammatically Carles represented the structure of a perfume in the form of a triangle divided horizontally into three sections representing the top, middle, and base notes, with the proportions between them as shown in Figure 9.1. A perfect example of a perfume formulated in this way is L Air du Temps. 

The division into top, middle, and base is of course somewhat arbitrary depending on where we draw the line between the three types of product. There is also considerable difference of opinion between perfumers as to the interpretation of evaporation tests carried out on smelling strips. Helmut Fuhrer (1970), for example, places benzyl salicylate and methyl ionone among the top notes, while Carles (rightly in our opinion) includes them among the base notes. The curious placing of benzyl salicylate by Fuhrer may perhaps be explained by its apparent weakness of odor particularly after any trace impurities have evaporated. Methyl ionone we would place near the top of the base... 

Created in 1948, L Air du Temps is a perfect example of a perfume belonging to what we have described as the middle period of perfumery, formulated around a structure composed of well-defined top, middle, and base notes. Its extraordinary simplicity, relying on natural products to give complexity and richness, not only makes it one of the most distinctive of perfumes but also a natural starting point for many derivative and often much more complex types of formula. 

The base note also contains the important accord between methyl ionone (10%), vetiveryl acetate, sandalwood, musk ketone, and originally musk ambrette. These materials together with the carnation make up the immediately recognizable central character of the perfume. 

As we would expect the perfume is clearly composed around a classical structure of top, middle, and base notes. Apart from all the essential elements of a chypre there is the bold use of strong materials such as citronellal (1%), the aliphatic aldehydes (1%), styrallyl acetate (4%), and styrax in an accord that gives the perfume its enormous individuality. It was also part of Carles s technique to take structural materials such as vetiveryl acetate, methyl ionone, and hydroxycitronellal and dress them up with a number of natural and synthetic ma-... 

A conventional jasmin base again provides the main floral aspect of the perfume. In more modem versions, for example, as in the Eau de Toilette, Lyral is used to replace part or all of the hydroxycitronellal. The styrax note may be reinforced by the use of phenylpropyl alcohol, one of its major constituents. The base note, in many ways similar to that of Ma Griffe, differs in the very much higher level of patchouli (10%). 

The typical chypre base note contains patchouli (6%), methyl ionone (the beta form was used in Aramis), vetiveryl acetate, cedryl acetate, oakmoss, and animalic notes. It is interesting also to find aldehyde Cl 8 being used in a similar way to that of aldehyde C14 in many of the earlier chypres. An important part of the amber character comes from the use of Dynamone, a speciality material derived from cistus, difficult to use, but of great diffusion and persistence. 

Taking the top, middle, and base notes as we have described them so far, we have what can be thought of as a classically formulated perfume, similar in its structural proportions to perfumes such as Madame Rochas. But in addition to this, there has been added, as if by a stroke of perfumery genius, some 20-25% of Hedione, working throughout the perfume, giving life and diffusion to the whole, and a... 

Over the past ten years the tendency toward the creation of monolithic perfumes, rather than those with a classic type of stmcture based on top, middle, and base notes, has seen the emergence of a new style of perfumery technique, which finally came of age with the creation of such perfumes as Tresor (Lancome 1990), Casmir (Chopard 1991), Dune (Dior 1991), and Spellbound (Lauder 1991). This technique has provided the inspiration—no doubt with the aid of information coming from GC analysis—for the launch, in quick succession, of a new generation of perfumes, which amounts to a revolution in the world of creative perfumery. 

The volatility of a perfume material determines its staying power. The more volatile materials are the ones that evaporate more quickly they tend to dominate the top note of a perfume and to be evident, for example, when sniffing at a freshly opened bottle or jar of a perfumed product or when examining the material on a freshly dipped blotter. The least volatile materials are the ones that stay around, even on fabrics after washing with a perfumed detergent they are most noticeable in the base note of a complex perfume. Limonene and benzyl acetate, for example, have high volatility synthetic musks and benzyl salicylate have low volatility. 

The aesthetic requirements of the new application may demand greater or lesser emphasis on the top note or the base note. 

Examples of case 3 are the adaptation of an alcoholic fragrance for use in body lotions, skin creams, or room fragrances. In all three cases both top and base note should be deemphasized in favor of the heart note. In an extended use room fragrance, in particular, the range of volatility of the components should be reduced as much as possible in order to achieve constancy of odor character. 

Apart from the creativity that expresses itself in novel odor accords and effects, there is also the inventiveness that leads to new solutions to such problems as masking the base note of a particularly unpleasant-smelling functional product or achieving outstanding diffusion and lasting power in a low-price soap perfume. The question whether the two—we might call them aesthetic and technical creativity—are different in kind has long divided the perfumery profession. Suffice it to say that technical creativity is, from a commercial point of view, every bit as valuable as the aesthetic kind. 

---