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PhF behaves rather differently from other halobenzene derivatives owing to the pi-donor properties of fluoride. For example, the para position is more activated than benzene toward electrophiles. For this reason, it can be converted to 1-bromo-4-fluorobenzene with relatively high efficiency. [3]
Download as PDF; Printable version; In other projects Wikidata item; Appearance. ... Halobenzene may also refer to any of the monosubstituted halobenzenes: Fluorobenzene;
Neurofibrillary tangles are formed by hyperphosphorylation of a microtubule-associated protein known as tau, causing it to aggregate, or group, in an insoluble form.(These aggregations of hyperphosphorylated tau protein are also referred to as PHF, or "paired helical filaments").
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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.
A few types of aromatic compounds, such as phenol, will react without a catalyst, but for typical benzene derivatives with less reactive substrates, a Lewis acid is required as a catalyst. Typical Lewis acid catalysts include AlCl 3, FeCl 3, FeBr 3 and ZnCl 2. These work by forming a highly electrophilic complex which is attacked by the benzene ...
In 1962 a book by U.S. biologist Rachel Carson (Carson 1962) started a storm of concerns about environmental pollution, first focused on DDT and other pesticides, some of them also halocarbons. These concerns were amplified when in 1966 Danish chemist Soren Jensen reported widespread residues of PCBs among Arctic and sub-Arctic fish and birds ...