Alcohols, nomenclature higher

The nomenclature of starch components has become highly confused through the indiscriminate use of such terms as a and /3-amylose, amylose and amylopectin, amyloamylose and erythroamylose, etc. It does not seem advisable to apply any of these older terms to the new and unique fractions obtained by selective precipitation methods. It is therefore proposed that the term A-fraction be applied to that portion of the starch which is preferentially precipitated by various alcohols or by higher fatty acids, and which exhibits a high affinity for iodine. Correspondingly, the residual non-precipitated portion of the starch, which possesses low iodine affinity, is termed the B-fraction. These designations apply to laboratory-prepared samples, and do not carry any a priori connotations of purity, homogeneity, or structure. 

In Section 8.1, we saw that a carbonyl group has a higher nomenclature priority than an alcohol or an amine group. However, all carbonyl compounds do not have the same priority. The nomenclature priorities of the various carbonyl groups are shown in Table 18.1. 

The experimental observations may, therefore, be rationalized by assuming that the 72-DNDBCH-6-one will have a higher initial rate of reduction. As a result, incomplete reduction of RS-DNDBCH-6-one would be expected to yield a mixture of DNDBCH-6-ol enriched in R enantiomer. The unreacted DNDBCH-6-one should be enriched in S enantiomer. Therefore, (—)-alcohol and (—)-ketone may be assigned the R configuration (for a discussion of the application of R and S configurational nomenclature to biphenyls, see Cahn et al, 1956). The (-f)-alco-... 

As with ketones, the carbonyl of an aldehyde has a higher priority than the C=C of an alkene, the C C of an alkyne, or the OH of an alcohol. Note that the aldehyde unit is drawn using a shorthand version, -CHO. When the aldehyde unit (-CHO) is attached to a ring, a major modification in the name is required. Aldehyde 71, for example, is not named cyclohexanal. This name makes no sense because an aldehyde must have the CHO carbon labeled as Cl. Instead, the term carboxal-dehyde is used and 71 is named cyclohexanecarboxaldehyde. This nomenclature rule should be used for all molecules where the CHO unit is attached to a ring. 

The nomenclature of the higher sugars and of the corresponding alcohols (glycitols) and acids has undergone considerable modification. When synthesized from the hexoses by the cyanohydrin synthesis of Kiliani, two hep-toses are derived from each hexose. Emil Fischer adopted the convention of naming the first isomer that was isolated as the a-heptonic acid and the... 

---