C monomethyl

Upon methylation of /) -dehydroindolizidine (55), dialkylated compounds 115 and 116 are formed in addition to C-monomethylated product 114. Compound 115 is accessible also by methylation of 8-methyl-zJ -dehydro-quinolizidine (//i). 

The reactivity of lactams towards bases and acids is greatly affected by substituents. For example, in the polymerization of C-monomethyl- --caprolactams in the presence of water, the rate decreases with the methyl... 

Let us start with the three isomeric C-monomethylated species (the toluidines or methyl-benzenamines) and accept the recent experimental measurements and analysis17. This source points out the contradictory and incomplete measurements for these species and uses the expression in disarray to describe the literature. From thermoneutral equation 2, we would predict enthalpies of formation of —12, —5 and 55 kJ mol-1 for all three solid, liquid and gaseous toluidines, in reasonable agreement with the experimental values. We note that the o-isomer is slightly more stable than its m- and p-isomers. In comparison, the spread of enthalpy of formation values for the isoelectronic and isosteric xylenes is but 1 kJ mol 1 and for the so-related methylphenols3 (cresols) is but 7 kJ mol 1. As an additional check for thermochemical accuracy, consider the formal methylation reaction 4. For Ar = Ph, the enthalpies of reaction are —36.6 (lq) and —32.2 (g) kJ mol 1. For Ar = C6H4NH2, the ortho, meta and para gas-phase enthalpies of reaction are the... 

On Fig. 5 the selectivities towards O- and C-monomethylated products are plotted as functions of the amount of benzoic acid adsorbed per unit surface area, [m ], of the catalyst (characteristic of surface basicity). The O/C alkylation ratio is seen to go down when basicity increased. 0-alkylation is reduced with a concomitant increase in C-alkylation, but the ring methylation stays preferentially ortho-selective. It was possible to change the selectivity towards 3-methyl catechol about 10 times, from 0.06 to 0.65, by varying the acid/base character of the catalyst surface without observing any significant change in the selectivity towards 4-methyl catechol. 

Equation (c) Monomethyl aniline i.e., a secondaiy aiyl amine, rmdergoes benzoylation to produce N-methyl phenyl benzamide or benzoyl monomethylaniline plus one mole of HCl. 

Figure 6.12 Chromatography and mass spectrometry of plant waxes. (1) Thin-layer chromatogram of broccoli leaf wax and gas-liquid chromatogram of the hydrocarbon fraction isolated from this wax. (2) Partial gas-liquid chromatogram of the alkane fraction from the surface lipids of tobacco leaves. (3) Partial gas-liquid chromatograms of the hydrocarbons from N. muscorum illustrating resolution of 8- (a), 7- (b) and 6- (c) monomethyl heptadecanes on a 750ft capillary column. (A)-(C) Partial mass spectra taken at points indicated in (2) illustrating identification of n- and branched alkanes. Reproduced with permission from Kolattukudy (1980).

Poly(vinylpyrrolidone-c -monomethyl itaconate) Chromatography Tetrahydrofuran SEC, ultrastyragel 2692... 

Tertiary amines containing one alkyl and two aryl groups, such as mono-I ncthyldiphenyhiniir.e, Cl l3(C, l l.diX , arc rarely encountered and arc unimportant. They usually react with nitrous acid with the insertion of a nitroso group into only one of the two available para positions monomethyl-diphenylamine thus gives monomethyl-mono - pnitroso-diphenylamine. Cl hj(C.ill .)N C l 1 jXO, or V-nicthyl-p-nitrosodiphcnylaniine. 

Davies and Warren have investigated the nitration of naphthalene, ace-naphthene and eight dimethylnaphthalenes in acetic anhydride at o °C. Rates relative to naphthalene were determined by the competition method, and the nitro-isomers formed were separated by chromatographic and identified by spectrophotometric means. The results, which are summarised in the table, were discussed in terms of various steric effects, and the applicability of the additivity rule was examined. For the latter purpose use was made of the data of Alcorn and Wells (table 10.2) relating to the nitration of monomethyl-naphthalenes at 25 °C. The additivity rule was found to have only limited utility, and it was suggested that the discrepancies might be due in part to the... 

The normal boiling point of 2-methylthiazole is 17 0= 128.488 0.005°C. The purity of various thiazoles was determined cryometrically by Handley et al. (292), who measured the precise melting point of thiazole and its monomethyl derivatives. Meyer et al. (293, 294) extended this study and, from the experimental diagrams of crystallization (temperature/degree of crystallization), obtained the true temperatures of crystallization and molar enthalpies of fusion of ideally pure thiazoles (Table 1-43). 

In normal practice, inhibitors such as hydroquinone (HQ) [123-31 -9] or the monomethyl ether of hydroquinone (MEHQ) [150-76-5] are added to acrylic monomers to stabilize them during shipment and storage. Uninhibited acrylic monomers should be used prompdy or stored at 10°C or below for no longer than a few weeks. Improperly iahibited monomers have the potential for violent polymerizations. HQ and MEHQ require the presence of oxygen to be effective inhibitors therefore, these monomers should be stored in contact with air and not under inert atmosphere. Because of the low concentration of inhibitors present in most commercial grades of acrylic monomers (generally less than 100 ppm), removal before use is not normally required. However, procedures for removal of inhibitors are available (67). 

Various ways of overcoming the PTA oxidation problem have been incorporated into commercial processes. The predominant solution is the use of high concentrations of manganese and cobalt ions (2,248—254), optionally with various cocatalysts (204,255,256), in the presence of an organic or inorganic bromide promoter in acetic acid solvent. Operational temperatures are rather high (ca 200°C). A lesser but significant alternative involves isolation of intermediate PTA, conversion to methyl/)-toluate, and recycle to the reactor. The ester is oxidized to monomethyl terephthalate, which is subsequentiy converted to DMT and purified by distillation (248,257—264). 

Hydrolysis of Dimethyl Terephthalate. Hoechst Celanese and Eormosa Chemical Eibers Corp. produce a polymer-grade terephthahc acid by hydrolysis of high purity dimethyl terephthalate. Hbls-Troisdorf AG hcenses a process with this step (70). Hydrolysis occurs at 260—280°C and 4500—5500 kPa (45—55 atm) in a hydrolysis reactor without catalysis. The overhead methanol and water vapor is separated and the methanol is returned to the dimethyl terephthalate section for reuse. The reactor hquid is crystallized, cycloned, washed, and further cooled. Einahy, the slurry is centrifuged and dried. The product has less than 25 ppm of 4-formylbenzoic acid and very low levels of other impurities. There may be several hundred parts per million of monomethyl terephthalate, which is incompletely hydrolyzed dimethyl terephthalate. 

Temperatures in excess of 140°C are required to complete the reaction and pressurized equipment is used for alcohols boiling below this temperature provision must be made for venting ammonia without loss of alcohol. The reaction is straightforward and, ia the case of the monomethyl ether of ethylene glycol [109-86-4] can be carried out at atmospheric pressure usiag stoichiometric quantities of urea and alcohol (45). Methylolation with aqueous formaldehyde is carried out at 70—90°C under alkaline conditions. The excess formaldehyde needed for complete dimethylolation remains ia the resia and prevents more extensive usage because of formaldehyde odor problems ia the mill. 

Sulfates having alkyl groups from methyl to pentyl have been examined. With methyl as an example, the hydrolysis rate of dimethyl sulfate iacreases with the concentration of the sulfate. Typical rates ia neutral water are first order and are 1.66 x lO " at 25°C and 6.14 x lO " at 35°C (46,47). Rates with alkaH or acid depend on conditions (42,48). Rates for the monomethyl sulfate [512-42-5] are much slower, and are nearly second order ia base. Values of the rate constant ia dilute solution are 6.5 X 10 L/(mol-s) at 100°C and 4.64 X 10 L/(mol-s) at 138°C (44). At 138°C, first-order solvolysis is ca 2% of the total. Hydrolysis of the monoester is markedly promoted by increasing acid strength and it is first order. The rate at 80°C is 3.65 x lO " ... 

Seb cic Acid. Sebacic acid [111-20-6] C QH gO, is an important intermediate in the manufacture of polyamide resins (see Polyamides). It has an estimated demand worldwide of approximately 20,000 t/yr. The alkaline hydrolysis of castor oil (qv), which historically has shown some wide fluctuations in price, is the conventional method of preparation. Because of these price fluctuations, there have been years of considerable interest in an electrochemical route to sebacic acid based on adipic acid [124-04-9] (qv) as the starting material. The electrochemical step involves the Kolbn-type or Brown-Walker reaction where anodic coupling of the monomethyl ester of adipic acid forms dimethyl sebacate [106-79-6]. The three steps in the reaction sequence from adipic acid to sebacic acid are as follows ... 

Phenylpteridine and its 4- and 7-monomethyl, 4,7- and 6,7-dimethyl and 4,6,7-trimethyl derivatives (69JCS(C)1408), as well as the coijresponding 4-phenylpteridine series and its 2- and 7-methyl, 2,7- and 6,7-dimethyl and 2,6,7-trimethyl derivatives (69JCS(C)1883), exist as neutral molecules in aqueous solution, essentially as unhydrated species. In acid solution 2- and 4-phenylpteridine and its 4- and 2-methyl derivatives favour the 5,6,7,8-dihydrated cation state, while 7-mono- or 6,7-disubstitution shifts the equilibrium mixture towards the 3,4-monohydrates. 

It is noteworthy that only in the case of dehydroquinolizidine derivatives does monomethylation produce the N-alkylated product. The formation of dialkylated products can be explained by a disproportionation reaction of the monoalkylated immonium salt caused by either the basicity of the starting enamine or some base added to the reaction mixture (most often potassium carbonate) and subsequent alkylation of the monoalkylated enamine. Reinecke and Kray 113) try to explain the different behavior of zJ -dehydroquinolizidine and zJ -dehydroquinolizidine derivatives by the difference in energies of N- and C-alkylation transition states because of the presence of I strain. 

The 2-phenyl-2-ethyl-pentane-1,5-diacid-mononitrile-(1) of melting point 72° to 76°C, used as starting material in this process, can be produced for example from o-phenyl-butyric acid nitrile by condensation with acrylic acid methyl ester and subsequent hydrolysis of the thus-obtained 2-phenyl-2-ethyl-pentane-1,5-diacid-monomethyl ester-mononltrile-(l) of boiling point 176° to 185°C under 12 mm pressure. 

A two-step methanolysis-hydrolysis process37 has been developed which involves reaction of PET with superheated methanol vapors at 240-260°C and atmospheric pressure to produce dimethyl terephthalate, monomethyl terephthalate, ethylene glycol, and oligomeric products in the first step. The methanolysis products are fractionally distilled and the remaining residue (oligomers) is subjected to hydrolysis after being fed into the hydrolysis reactor operating at a temperature of ca. 270°C. The TPA precipitates from the aqueous phase while impurities are left behind in the mother liquor. Methanolysis-hydrolysis leads to decreases in the time required for the depolymerization process compared to neutral hydrolysis for example, a neutral hydrolysis process that requires 45 min to produce the monomers is reduced... 

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