Chemical Structure / July 25, 2018 / Reina Huffman
This is a measure of the three-dimensional fusion of carbon black particles to form aggregates, which may contain a large number of particles. The shape and degree of branching of the aggregates is referred to as structure. Highly structured carbon blacks provide higher viscosity, greater electrical conductivity and easier dispersion for specialty carbon blacks. Measures of aggregate structure may be obtained from shape distributions from EM analysis, oil absorption (OAN) or void volume analysis.
It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula (C6H5)2. It is notable as a starting material for the production of polychlorinated biphenyls (PCBs), which were once widely used as dielectric fluids and heat transfer agents. Biphenyl is also an intermediate for the production of a host of other organic compounds such as emulsifiers, optical brighteners, crop protection products, and plastics. Biphenyl is insoluble in water, but soluble in typical organic solvents.
Pure avobenzone is a whitish to yellowish crystalline powder with a weak odor, dissolving in isopropanol, decyl oleate, capric acidcaprylic acid triglycerides and other oils. Avobenzone is a dibenzoylmethane derivative. Avobenzone exists in the ground state as a mixture of the enol and keto forms, favoring the chelated enol. This enol form is stabilized by intramolecular hydrogen-bonding within the β-diketone. Its ability to absorb ultraviolet light over a wider range of wavelengths than many other sunscreen agents has led to its use in many commercial preparations marketed as "broad spectrum" sunscreens. Avobenzone has an absorption maximum of 357 nm.
Benzidine is prepared in a two step process from nitrobenzene. First, the nitrobenzene is converted to 1,2-diphenylhydrazine, usually using iron powder as the reducing agent. Treatment of this hydrazine with mineral acids induces a rearrangement reaction to 4,4'-benzidine. Smaller amounts of other isomers are also formed. The benzidine rearrangement, which proceeds intramolecularly, is a classic mechanistic puzzle in organic chemistry.
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