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The p-xylene is then separated out in a series of distillation, adsorption or crystallization and reaction processes from the m-xylene, o-xylene, and ethylbenzene. Its melting point is the highest among this series of isomers, but simple crystallization does not allow easy purification due to the formation of eutectic mixtures.
for p-Xylene/carbon tetrachloride [6] P = 760 mm Hg BP Temp. °C % by mole carbon tetrachloride liquid ... Spectrum NIST: Major absorption bands 793.94 cm −1: NMR;
p-Xylene is the principal precursor to terephthalic acid and dimethyl terephthalate, both monomers used in the production of polyethylene terephthalate (PET) plastic bottles and polyester clothing. 98% of p-xylene production, and half of all xylenes produced is consumed in this manner. [10] [14] o-Xylene is an important precursor to phthalic ...
Figure 2 shows the distinct VUV spectra of m-, p-, and o-xylene. These compounds can be differentiated despite their only difference being the position of two methyl groups around a benzene ring. The spectral differences of these isomers enable their co-elution to be resolved through spectral deconvolution.
o-Xylene (ortho-xylene) is an aromatic hydrocarbon with the formula C 6 H 4 (CH 3) 2, with two methyl substituents bonded to adjacent carbon atoms of a benzene ring (the ortho configuration). It is a constitutional isomer of m-xylene and p-xylene, the mixture being called xylene or xylenes. o-Xylene is a colourless slightly oily flammable ...
α,α'-dimethoxy-p-xylene. A similar synthesis for parylene N uses the precursor α,α'-dimethoxy-p-xylene. [28] The methoxy group H 3 CO − is the leaving group; while it condenses in the deposition chamber, it does not interfere with the deposition of the polymer. [23] This precursor is much less expensive than [2.2]para-cyclophane.
Alkylbenzene isomers can be differentiated by observing the position of alkyl substituents on the benzene ring using chemical ionization-proton exchange mass spectrometry. Conventional GC-MS yields limited results because the isomers have identical molecular weight and substituents.
Despite the observed chemistry of para-xylylene (i.e. its rapid polymerization to poly-p-xylylene), which suggests the compound exists as a diradical, physical evidence unanimously concludes that the lowest electronic state of p-xylylene is a closed shell singlet. Additionally, several computational methods confirm this assignment. [13]