11 Nuclear magnetic resonance ethyl acetate

C Nuclear magnetic resonance spectrum, acetaldehyde, 732 acetophenone, 732 anisole, 672 benzaldehyde, 732 benzoic acid, 771 p-bromoacetophenone, 449 2-butanone, 449, 732 crotonic acid. 771 cyclohexanol, 634 cyclohexanone, 732 ethyl benzoate, 477 methyl acetate, 443 methyl propanoate, 450 methyl propyl ether, 672... 

Four kauranes present in the petroleum ether/ethyl acetate fractions of nemoralis were fully characterized by mass spectrometry, nuclear magnetic resonance spectrometry and infrared as (-)-kaur-16-en-19-oic acid, (-)-kauran-16 <-ol, 15sC-hydroxy-(-)-kaur-16-en-19-oic acid and 17-hydroxy-(-)-kaur-15-en-19-oic acid... 

Notes LOD, limit of detection MeOH, methanol EtOH, ethanol ACN, acetonitrile EtAC, ethyl acetate SPE, solid phase extraction HLB (hydrophilic lipophilic balanced) TFA, trifluoroacetic acid GC, gas chromatography TMS, trimethylsilyl MS, mass spectrometry HPLC, high-performance liquid chromatography DAD, diode array detector NMR, nuclear magnetic resonance ESI, electrospray ionization APCI, atmospheric pressure chemical ionization CE, capillary electrophoresis ECD, electrochemical detector CD, conductivity detector TLC, thin layer chromatography PDA, photodiode array detector. 

The assembly of the carbon skeletons of these unusual hydrocarbons was first studied in Carpophilus freemani Dobson, through careful GC-MS and Nuclear Magnetic Resonance (NMR) studies of the incorporation of 2H or 13C-labeled precursors (Petroski et al., 1994). Assembly of the carbon skeleton of the aggregation pheromone of C. freemani, (2 , 4 , 6ii)-5-ethyl-3-methyl-2,4,6-nonatriene, involves initiation with acetate elongation with first propionate (to provide the methyl branch), then butyrate (to provide the ethyl branch) and chain termination with a second butyrate (Figure 6.7). At some point, loss of C02 from one of the butyrate units occurs to yield the appropriate hydrocarbon, but Petroski et al. (1994) were unable to determine which of the butyrate units loses its carboxyl group. Bartelt and Weisleder (1996) studied the biosynthesis of 15 additional methyl- and/or ethyl-branched, tri- and tetraenes in the related... 

The solid catalyst was recovered by filtration on fritted glass and washed with ethyl acetate. The solution was analyzed by gas phase chromatography, and the nature of the final products was confirmed by a complete spectroscopic analysis (infrared, nuclear magnetic resonance, mass spectrometry). 

Many cellulose derivatives form lyotropic liquid crystals in suitable solvents and several thermotropic cellulose derivatives have been reported (1-3) Cellulosic liquid crystalline systems reported prior to early 1982 have been tabulated (1). Since then, some new substituted cellulosic derivatives which form thermotropic cholesteric phases have been prepared (4), and much effort has been devoted to investigating the previously-reported systems. Anisotropic solutions of cellulose acetate and triacetate in tri-fluoroacetic acid have attracted the attention of several groups. Chiroptical properties (5,6), refractive index (7), phase boundaries (8), nuclear magnetic resonance spectra (9,10) and differential scanning calorimetry (11,12) have been reported for this system. However, trifluoroacetic acid causes degradation of cellulosic polymers this calls into question some of the physical measurements on these mesophases, because time is required for the mesophase solutions to achieve their equilibrium order. Mixtures of trifluoroacetic acid with chlorinated solvents have been employed to minimize this problem (13), and anisotropic solutions of cellulose acetate and triacetate in other solvents have been examined (14,15). The mesophase formed by (hydroxypropyl)cellulose (HPC) in water (16) is stable and easy to handle, and has thus attracted further attention (10,11,17-19), as has the thermotropic mesophase of HPC (20). Detailed studies of mesophase formation and chain rigidity for HPC in dimethyl acetamide (21) and for the benzoic acid ester of HPC in acetone and benzene (22) have been published. Anisotropic solutions of methylol cellulose in dimethyl sulfoxide (23) and of cellulose in dimethyl acetamide/ LiCl (24) were reported. Cellulose tricarbanilate in methyl ethyl ketone forms a liquid crystalline solution (25) with optical properties which are quite distinct from those of previously reported cholesteric cellulosic mesophases (26). 

Scheme 43 outlines the reaction of aroylthioureas 56 with 3 in dry ethyl acetate under N2 and chromatographic separation to yield 139. Mechanistically, the formation of 139 was explained by the addition of the sulfur of 57 to the nitrile group in 3 (Scheme 43). Intermediate 137 then undergoes a hydrogen shift to give 138 followed by cychzation to give the stable heterocycles 139 (Scheme 43). Nuclear magnetic resonance spectra excluded the formation of spiroindolothiazines 140, since all the data are consistent with indeno[l,2-

The cyclic structure of the polymers [31] was substantiated by infrared and chemical evidence. The fact that they were soluble (acetone, methyl ethyl ketone, acetic acid, dioxane) confirms their linear character. The polymerizations were also initiated by other radical initiators [peroxides, azobis(iso-butyronitrile)]. Carbinols with aliphatic, cycloaliphatic, and aromatic substituents were polymerized (104,106,109, 111, 113,119-121). Cyclic polymers are also obtained from their acetates and ethers (107, 113). Nuclear magnetic resonance has been employed to study transitions in these polymers (75, 76). Polymers possessing molecular weights of over 1,000,000 resulted in some cases. The kinetics of polymerization (11-14) were studied (111, 112). Copolymerization with vinyl monomers (108, 145) yielded linear, soluble polymers that contained cyclic structures derived from the vinylethynyl carbinol. 

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