Search results
Results from the WOW.Com Content Network
The methoxide anion, for example, is both a strong base and nucleophile because it is a methyl nucleophile, and is thus very much unhindered. tert -Butoxide , on the other hand, is a strong base, but a poor nucleophile, because of its three methyl groups hindering its approach to the carbon.
The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br under basic conditions, where the attacking nucleophile is hydroxyl (OH −) and the leaving group is bromide (Br −).
As the name suggests, a non-nucleophilic base is a sterically hindered organic base that is a poor nucleophile.Normal bases are also nucleophiles, but often chemists seek the proton-removing ability of a base without any other functions.
The Edwards equation in organic chemistry is a two-parameter equation for correlating nucleophilic reactivity, as defined by relative rate constants, with the basicity of the nucleophile (relative to protons) and its polarizability. This equation was first developed by John O. Edwards in 1954 [1] and later revised based on additional work in ...
However, this problem can be avoided if one of the compounds does not contain an α-hydrogen, rendering it non-enolizable. In an aldol condensation between an aldehyde and a ketone, the ketone acts as the nucleophile, as its carbonyl carbon does not possess high electrophilic character due to the +I effect and steric hindrance. Usually, the ...
Some examples of nucleophiles include doubly stabilized carbon nucleophiles such as beta-ketoesters, malonates, and beta-cyanoesters. The resulting product contains a highly useful 1,5-dioxygenated pattern. Non-carbon nucleophiles such as water, alcohols, amines, and enamines can also react with an α,β-unsaturated carbonyl in a 1,4-addition. [10]
the base is a poor nucleophile. Bases with steric bulk, (such as in potassium tert-butoxide), are often poor nucleophiles. For example, when a 3° haloalkane is reacts with an alkoxide, due to strong basic character of the alkoxide and unreactivity of 3° group towards S N 2, only alkene formation
If the nucleophile is a neutral molecule (i.e. a solvent) a third step is required to complete the reaction. When the solvent is water, the intermediate is an oxonium ion. This reaction step is fast. Deprotonation: Removal of a proton on the protonated nucleophile by water acting as a base forming the alcohol and a hydronium ion. This reaction ...