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Tetramethyl orthosilicate (TMOS) is the chemical compound with the formula Si(OCH 3) 4.This molecule consists of four methoxy groups bonded to a silicon atom. The basic properties are similar to the more popular tetraethyl orthosilicate, which is usually preferred because the product of hydrolysis, ethanol, is less toxic than methanol.
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In nature, methoxy groups are found on nucleosides that have been subjected to 2′-O-methylation, for example in variations of the 5′-cap structure known as cap-1 and cap-2. They are also common substituents in O -methylated flavonoids , whose formation is catalyzed by O-methyltransferases that act on phenols , such as catechol- O -methyl ...
The +M effect, also known as the positive mesomeric effect, occurs when the substituent is an electron donating group. The group must have one of two things: a lone pair of electrons, or a negative charge. In the +M effect, the pi electrons are transferred from the group towards the conjugate system, increasing the density of the system.
Random variables are usually written in upper case Roman letters, such as or and so on. Random variables, in this context, usually refer to something in words, such as "the height of a subject" for a continuous variable, or "the number of cars in the school car park" for a discrete variable, or "the colour of the next bicycle" for a categorical variable.
Confounding, in statistics, an extraneous variable in a statistical model that correlates (directly or inversely) with both the dependent variable and the independent variable; Hidden transformation, in computer science, a way to transform a generic constraint satisfaction problem into a binary one by introducing new hidden variables
Different ways of representing a methyl group (highlighted in blue). In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula CH 3 (whereas normal methane has the formula CH 4).
Ortho effect is an organic chemistry phenomenon where the presence of a chemical group at the at ortho position or the 1 and 2 position of a phenyl ring, relative to the carboxylic compound changes the chemical properties of the compound.