Overall conversion related yield

In reaction scheme 1, the selectivity of has the same value as the overall conversion related yield in equation (2.27). In the case of reaction scheme 2, however, these two parameters are different, i.e. ... 

Absolute potential at the electrode surface Overall conversion related yield Absolute potential of the bulk solution phase Absolute potential at the plane of closest approach of cations Potential field strength Rotation rate... 

The conversion of alcohols directly into the structurally related hydrocarbons by ionic hydrogenation can provide a means of synthesis for compounds that would be extremely difficult or impossible to obtain by other methods. A good example is the synthesis of 2-terr-butyladamantane (12, R = Me). This interesting, highly strained compound may be synthesized in moderate overall yield by a conventional multiple-step route.149 Alternatively, it is obtained in 90% isolated yield upon treatment of a dichloromethane solution of the readily available 2-/c/7-bulyI -2-adamantanoI (11, R = Me)150 and one equivalent of either tri-n-hexylsilane151152 or triethylsilane153 with trifluoroacetic acid at room temperature (Eq. 16). 

The diastereomerically related keto esters 53 and 55, activated for removal of the chiral auxiliary, were obtained from 5 and 9. The requisite nitrogen atom was introduced by an azide displacement of chloride and at an opportune stage of the synthesis an intramolecular aminolysis of the carboxylic ester provided the enantiomerically related keto lactams 54 and 56. Although shorter routes to these popular synthetic targets have been reported in recent years, the conversion of 9 to (—)-iso-nitramine (ten steps, 50% overall yield) clearly illustrates the efficiency of the asymmetric Birch reduction-alkylation strategy for construction of the azaspiroundecane ring system. 

The 1,4-addition of alkyl cyanocupratcs to epoxides to form cyclic a,ft-unsalurated ketones provides a stereoselective method for conversion of dehydro-. cpiandrosteronc into cholesterol (4) and other related steroids. Thus the keto epoxide 2 (obtained from dehydroepiandrosterone in 55% overall yield in three steps) reacts with lithium isohcxylcyanocupratc to give the adduct 3, which can be converted to cholesterol (4) in several known steps.27... 

It was pointed out earlier that Equations 11 and 12 do not apply at feed conversion outside the range of commercial operating conditions. In this regime, feed conversion must be calculated from the rate constant integrated via Equation 10. It remains to complete the overall model by developing a correlation to relate pyrolysis yields to process operating parameters and feed conversion. 

A complex system is one in which more than one reaction occurs. This can lead to ijiultiple products, some of which are more desirable than others from a practical standpoint. For example, in the air oxidation of ethylene the desired product is ethylene oxide, but complete oxidation to carbon -dioxide and—water—alse-0eeu-FS--The-im-perta-nt-per-for-ma-nee-factor-is-i he production rate of ethylene oxide and its purity in the reaction products, rather than the total amount of ethylene reacted. To characterize this performance two parameters are used yield and selectivity. The yield of a specific product is defined as the fraction of reactant converted to that product. The point selectivity is the ratio of the rate of production of one product to the rate for another product. With multiple products there is a separate selectivity based on each pair of products. The overall, or integrated, selectivity is the ratio of the amount of one product produced to the amount of another. Selectivity and yield are related to each other through the total conversion, i.e., the total fraction of reactant converted to all products. 

More complex systems such as 449, which is structurally related to a class of powerful muscarinic agonists, are easily constructed using this methodology as well [139] (Scheme 63). The conversion 441 448 proceeds in 59% overall yield, and gives 448 as a 6 1 mixture of isomers. SnC -promoted rearrangement produces the highly functionalized tetrahydrofuran 449 with > 96% ee. 

---