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This is followed by a second condensation to form HMG-CoA (3-hydroxy-3- methyl-glutaryl-CoA). Reduction of HMG-CoA yields (R)- mevalonate . These first 3 enzymatic steps are called the upper mevalonate pathway.
A carbocation is an ion with a positively charged carbon atom. ... is indeed a stable carbocationic system, for example in the form of trityl hexafluorophosphate.
The alcohol is protonated, the H 2 O group formed leaves, forming a carbocation, and the nucleophile Cl − (which is present in excess) readily attacks the carbocation, forming the chloroalkane. Tertiary alcohols react immediately with Lucas reagent as evidenced by turbidity owing to the low solubility of the organic chloride in the aqueous ...
In the first step, the leaving group departs, forming a carbocation (C +). In the second step, the nucleophilic reagent (Nuc:) attaches to the carbocation and forms a covalent sigma bond. If the substrate has a chiral carbon, this mechanism can result in either inversion of the stereochemistry or retention of configuration. Usually, both occur ...
Whereas the carbon–helium-ion bond breaks spontaneously and immediately to yield a carbocation, bonds of other elements to helium are more stable. For example, molecular tritium T 2 or tritium-hydrogen HT. On decay, these form a stable helium hydride ion [HeH] + (respectively [3 HeT] + or [3 HeH] +), which is stable enough to persist. This ...
In this case, tertiary carbocation will react faster than a secondary which will react much faster than a primary. It is also due to this carbocation intermediate that the product does not have to have inversion. The nucleophile can attack from the top or the bottom and therefore create a racemic product.
Decarboxylation. Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO 2).Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain.
a carbocation by heterolysis in a nucleophilic rearrangement or anionotropic rearrangement; a carbanion in an electrophilic rearrangement or cationotropic rearrangement; a free radical by homolysis; a nitrene. The driving force for the actual migration of a substituent in step two of the rearrangement is the formation of a more stable intermediate.