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A hydrohalogenation reaction is the electrophilic addition of hydrogen halides like hydrogen chloride or hydrogen bromide to alkenes to yield the corresponding haloalkanes. [ 1 ] [ 2 ] [ 3 ] If the two carbon atoms at the double bond are linked to a different number of hydrogen atoms, the halogen is found preferentially at the carbon with fewer ...
The geologic time scale is a way of representing deep time based on events that have occurred throughout Earth's history, a time span of about 4.54 ± 0.05 Ga (4.54 billion years). [3] It chronologically organises strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or ...
The Gelasian was introduced in the geologic timescale in 1998. [6] It is named after the Sicilian city of Gela in the south of the island. In 2009 it was moved from the Pliocene to the Pleistocene so that the geologic time scale would be more consistent with the key changes in Earth's climate, oceans, and biota that occurred 2.58 million years ago.
Halogenation. In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide -containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. [1] This kind of conversion is in fact so common that a comprehensive overview is ...
haloform-reaction. RSC ontology ID. RXNO:0000689. In chemistry, the haloform reaction (also referred to as the Lieben haloform reaction) is a chemical reaction in which a haloform (CHX3, where X is a halogen) is produced by the exhaustive halogenation of an acetyl group (R−C (=O)CH3, where R can be either a hydrogen atom, an alkyl or an aryl ...
The dates for each age can vary by region. On the geologic time scale, the Holocene epoch starts at the end of the last glacial period of the current ice age (c. 10,000 BC) and continues to the present. The beginning of the Mesolithic is usually considered to correspond to the beginning of the Holocene epoch
Workers are breaching the final dams on a key section of the Klamath River on Wednesday, clearing the way for salmon to swim freely through a major watershed near the California-Oregon border for ...
Electrophilic halogenation. In organic chemistry, an electrophilic aromatic halogenation is a type of electrophilic aromatic substitution. This organic reaction is typical of aromatic compounds and a very useful method for adding substituents to an aromatic system. A few types of aromatic compounds, such as phenol, will react without a catalyst ...