The morphology and biaxial texture of vacuum evaporated CaF(2) films on amorphous substrates as a function of vapour incident angle, substrate temperature and film thickness were investigated by scanning electron microscopy, x-ray pole figure and reflection high energy electron diffraction surface pole figure analyses. Results show that an anomalous [220] out-of-plane texture was preferred in CaF(2) films deposited on Si substrates at < 200 °C with normal vapour incidence. With an increase of the vapour incident angle, the out-of-plane orientation changed from [220] to [111] at a substrate temperature of 100 °C. In films deposited with normal vapour incidence, the out-of-plane orientation changed from [220] at 100 °C to [111] at 400 °C. In films deposited with an oblique vapour incidence at 100 °C, the texture changed from random at small thickness (5 nm) to biaxial at larger thickness (20 nm or more). Using first principles density functional theory calculation, it was shown that [220] texture formation is a consequence of energetically favourable adsorption of CaF(2) molecules onto the CaF(2)(110) facet.
An investigation has been made of the reactions of p-nitrophenoxide ion in methanol with equimolar quantities (0.01-0.02M) of the six monochlorodiaza-benzenes, viz. 3- and 4-chloropyridazine (1,2- diazabenzene); 2-, 4-, and 5-chloro-pyrimidines (1,3-diazabenzene); and 2-chloropyrazine (1,4-diazabenzene) in the presence of a tenfold excess (0.1-0.2M) of p-nitrophenol. Results have been compared with earlier results from the pyridine series, and reactivity shown to be in reasonable agreement with that predicted from kinetic data for the pyridine series assuming independent activation by each nitrogen. There is evidence for mild acid catalysis by the p-nitrophenol added to prevent concurrent methanolysis. It is estimated that this leads to an increase in Hammett substituent constant (σ-) values of only 0.2 units or less. The reactivity order is 2- > 4-chloro-N-methylpyridinium > 2- > 4- chloro-pyrimidine > 4-chloropyridazine≈3-chloropyridazine≈2- chloropyrazine>3-chloro-N-methylpyridinium≈5-chloropyrimidine, and this corresponds with the theoretical order as modified by mild acid catalysis, more effective in the order ortho-> meta- > para- to the point of substitution, and including the inverted order, 2- > 4- chloropyrimidine, whereas the usual reactivity order with anionic reagents is 4- > 2-chloropyrimidine.
The syntheses of 2-(2?,4?-dihydroxy-6?-methylbenzoyl)-3,6- dihydroxybenzoic acid (4) and its methyl ethers are described. Treatment of 6-hydroxy-2-(2?-hydroxy-4?-methoxy-6?-methylbenzoyl)-3- methoxybenzoic acid (8) with alcoholic potassium hydroxide gave 2- hydroxy-6-methoxy-8-methyl-9-oxoxanthene-1-carboxylic acid (9). Comparison of the p.m.r. spectra of these structurally related 2- benzoylbenzoic acids revealed that the chemical shifts of the aryl methyl and the ring protons are significantly influenced by the existence of intramolecular hydrogen bonding.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.