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In general, the larger a substituent's A-value, the larger the steric effect of that substituent. A methyl group has an A-value of 1.74 while tert-butyl group has an A-value of ~5. Because the A-value of tert-butyl is higher, tert-butyl has a larger steric effect than methyl. This difference in steric effects can be used to help predict ...
From comparing the E s values for methyl, ethyl, isopropyl, and tert-butyl, it is seen that the value increases with increasing steric bulk. However, because context will have an effect on steric interactions [7] some E s values can be larger or smaller than expected. For example, the value for phenyl is much larger than that for tert-butyl.
The tert-butoxide is a strong, non-nucleophilic base in organic chemistry. It readily abstracts acidic protons from substrates, but its steric bulk inhibits the group from participating in nucleophilic substitution, such as in a Williamson ether synthesis or an S N 2 reaction. tert-Butyl alcohol reacts with hydrogen chloride to form tert-butyl ...
The effect of the tert-butyl group on the progress of a chemical reaction is called the Thorpe–Ingold effect illustrated in the Diels-Alder reaction below. Compared to a hydrogen substituent, the tert-butyl substituent accelerates the reaction rate by a factor of 240. [2] tert-Butyl effect. The tert-butyl effect is an example of steric hindrance.
The steric effect of tri-(tert-butyl)amine makes electrophilic reactions, like forming the tetraalkyl ammonium cation, difficult. It is difficult for electrophiles to get close enough to allow attack by the lone pair of the nitrogen (nitrogen is shown in blue)
When multiple substituents are comparably activating, steric hindrance dominates regioselectivity. Substituents add ortho to the methyl group in para-(tert-butyl)toluene; In particular, the position between two substituents, each meta to the other, reacts last. New substituents add para to either substituent in meta-chlorotoluene
The amount on steric strain in similar molecules is dependent on the size of the interacting groups; bulky tert-butyl groups take up much more space than methyl groups and often experience greater steric interactions.
An example of a reaction taking place with an S N 1 reaction mechanism is the hydrolysis of tert-butyl bromide forming tert-butanol: This S N 1 reaction takes place in three steps: Formation of a tert-butyl carbocation by separation of a leaving group (a bromide anion) from the carbon atom: this step is slow. [5] Recombination of carbocation ...