Alkylated value

The a2-alkyl value is included in the a-alkyl value. The phenolic value is included in the aromatic value. 

Consider the case of 50% isobutane conversion. This is a magic number, for which product from an isobutane cracker is equimolar in olefins and isobutane (except for a minor total selectivity correction). This mixture could be fed directly to an alkylation unit. Total propylene plus isobutylene weight percent selectivity at atmospheric pressure is 65 wt %. The price spread of isobutane at approximately 1.89/bbl to alkylate value olefins at 4.62/bbl or better (these prices are equivalent to 2.20 cents/lb isobutylene and 2.53 cents/lb propylene) suggests that isobutane cracking may be significant in the near future by alleviating olefin demands for alkylate, in effect, releasing more propylene for chemical consumption. 

In a way, PP competes with gasoline production. If the price of gasoline goes high enough, the refinery takes propylene out and places it into production of gasoline for its alkylation value. This alternate use can be more profitable sometimes. 

Thus, the values calculated for effective polarizability at the nitrogen atom for a series of 49 amines carrying only alkyl groups was correlated directly with their proton affinities, a reaction that introduces a positive charge on the nitrogen atom by protonation (Figure 7-7) [40. ... 

Owing to the comparatively negligible difference in the cost of bromine and the equivalent quantity of constat boiling point hydrobromio acid, there is little to be gained—apart from the instructional value—in preparing the hydrobromio acid from bromine in the preparation of alkyl bromides. 

Esters of /i-toluenesulphonic acid, which are of great value as alkylating agents, may be prepared by interaction of p-toluenesulphonyl chloride and the alcdiol in the presence of sodium hydroxide solution or of pyridine, for example ... 

The selectivity of an electrophile, measured by the extent to which it discriminated either between benzene and toluene, or between the meta- and ara-positions in toluene, was considered to be related to its reactivity. Thus, powerful electrophiles, of which the species operating in Friedel-Crafts alkylation reactions were considered to be examples, would be less able to distinguish between compounds and positions than a weakly electrophilic reagent. The ultimate electrophilic species would be entirely insensitive to the differences between compounds and positions, and would bring about reaction in the statistical ratio of the various sites for substitution available to it. The idea has gained wide acceptance that the electrophiles operative in reactions which have low selectivity factors Sf) or reaction constants (p+), are intrinsically more reactive than the effective electrophiles in reactions which have higher values of these parameters. However, there are several aspects of this supposed relationship which merit discussion. 

The formation of the above anions ("enolate type) depend on equilibria between the carbon compounds, the base, and the solvent. To ensure a substantial concentration of the anionic synthons in solution the pA" of both the conjugated acid of the base and of the solvent must be higher than the pAT -value of the carbon compound. Alkali hydroxides in water (p/T, 16), alkoxides in the corresponding alcohols (pAT, 20), sodium amide in liquid ammonia (pATj 35), dimsyl sodium in dimethyl sulfoxide (pAT, = 35), sodium hydride, lithium amides, or lithium alkyls in ether or hydrocarbon solvents (pAT, > 40) are common combinations used in synthesis. Sometimes the bases (e.g. methoxides, amides, lithium alkyls) react as nucleophiles, in other words they do not abstract a proton, but their anion undergoes addition and substitution reactions with the carbon compound. If such is the case, sterically hindered bases are employed. A few examples are given below (H.O. House, 1972 I. Kuwajima, 1976). 

Alkyl halides and sulfonates are the most frequently used alkylating acceptor synthons. The carbonyl group is used as the classical a -synthon. O-Silylated hemithioacetals (T.H. Chan, 1976) and fomic acid orthoesters are examples for less common a -synthons. In most synthetic reactions carbon atoms with a partial positive charge (= positively polarized carbon) are involved. More reactive, "free carbocations as occurring in Friedel-Crafts type alkylations and acylations are of comparably limited synthetic value, because they tend to react non-selectively. 

Quantum chemistry methods allow the prediction of the ultraviolet transitions in good agreement with the experimental values in the case of thiazole and its three methyl derivatives (Table 1-18). A very weak absorption has been indicated at 269.5 nm that could correspond to an n- TT transition given by calculation at 281.5 nm (133). Ultraviolet absorption spectroscopy has been investigated in connection with steric interactions in the A-4-thiazoline-2-thione (74) series (181). It was earlier demonstrated by NMR technique that 4-alkyl-3 isopropyl-A-4-thiazoline-2-thiones exist in solution as equilibrium mixtures of two conformers (75 and 76), the relative populations of which vary with the size of R4 (182) for R4 = rBu the population of rotamer A is 100%, whereas for R4 = Me it is only 28%. Starting from the observed absorption wavelength for... 

The molar refraction deduced for alkyl derivatives, compared to the value obtained by addition, to the experimental molar refraction of thiazole, of the classical (CH2) increment of Eisenlohr Rch 4.618 cm ), show specific exaltations which are typical for each position of the thiazole ring (Table 1-49). 

Potentiometric determinations of the pK of thiazole and essentially its alkyl derivatives are summarized in Table T50. The most reliable values are given by Phan-Tan-Luu et al. (321), who realized a critical study of the classical Henderson method for the determination of pK. ... 

Here again it is possible to find a linear relationship between the log (k/feo) (ko = methyl) values of 2-alkyl- and 2,4-dialkylthiazoles and between the latter value and Tafts Eg parameter (256). The value of 5 for 2,4-dialkylthiazoles is 1.472 with a correlation coefficient of 0.9994. Thus the sensitivity to substituent effects is more marked than in the case of a single substituent in the 2-position. Furthermore, the 4-position is again more sensitive than the 2-position. 

Secondary and pnmary alcohols do not react with HCl at rates fast enough to make the preparation of the conespondmg alkyl chlorides a method of practical value There fore the more reactive hydrogen halide HBr is used even then elevated temperatures are required to increase the rate of reaction... 

Aryl diazonium ions prepared by nitrous acid diazotization of primary arylamines are substantially more stable than alkyl diazonium ions and are of enormous synthetic value Their use m the synthesis of substituted aromatic compounds is described m the following two sections... 

The value of alkyl halides as starting materials for the preparation of a variety of organic functional groups has been stressed many times In our earlier discussions we noted that aryl halides are normally much less reactive than alkyl halides m reactions that involve carbon-halogen bond cleavage In the present chapter you will see that aryl halides can exhibit their own patterns of chemical reactivity and that these reac tions are novel useful and mechanistically interesting... 

Ethers, such as MTBE and methyl / fZ-amyl ether (TAME) are made by a catalytic process from methanol (qv) and the corresponding isomeric olefin. These ethers have excellent octane values and compete on an economic basis with alkylation for inclusion in gasoline. Another ether, ethyl tert-huty ether (ETBE) is made from ethanol (qv) and isobutylene (see Butylenes). The cost and economic driving forces to use ETBE vs MTBE or TAME ate a function of the raw material costs and any tax incentives that may be provided because of the ethanol that is used to produce it. 

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