Search results
Results from the WOW.Com Content Network
For nitration, for example, fluorine directs strongly to the para position because the ortho position is inductively deactivated (86% para, 13% ortho, 0.6% meta). On the other hand, iodine directs to ortho and para positions comparably (54% para and 45% ortho, 1.3% meta). [12]
The methoxy group is an ortho/para directing group, which means that electrophilic substitution preferentially occurs at these three sites. The enhanced nucleophilicity of anisole vs. benzene reflects the influence of the methoxy group, which renders the ring more electron-rich.
Directed ortho metalation (DoM) is an adaptation of electrophilic aromatic substitution in which electrophiles attach themselves exclusively to the ortho-position of a direct metalation group or DMG through the intermediary of an aryllithium compound. [1] The DMG interacts with lithium through a hetero atom.
In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula R−O−CH 3 . On a benzene ring , the Hammett equation classifies a methoxy substituent at the para position as an electron-donating group , but as an electron-withdrawing group if at the meta position.
Groups with unshared pairs of electrons, such as the amino group of aniline, are strongly activating (some time deactivating also in case of halides) and ortho/para-directing by resonance. Such activating groups donate those unshared electrons to the pi system, creating a negative charge on the ortho and para positions. These positions are thus ...
It is compatible with a spectrum of substituted anilide as well as different bisaryliodonium salts. However, the meta-selectivity is lost when highly ortho/para-directing methoxy group substitutes one of the meta-hydrogen of the anilide, which marks the limitation of this method. highly ortho and para directing m-OMe overrides the meta-selectivity
The ortho effect also occurs when a meta-directing group is positioned in a meta arrangement relative to an ortho–para-directing group, a new substituent introduced into the molecule tends to preferentially occupy the ortho position relative to the meta-directing group rather than the para position.
For meta-directing groups (electron withdrawing group or EWG), σ meta and σ para are more positive than σ’. (The superscript, c, in table denotes data from Hammett, 1940. [11] [page needed]) For ortho-para directing groups (electron donating group or EDG), σ’ more positive than σ meta and σ para.