What is an deactivator in chemistry?

Last Update: May 30, 2022

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Deactivator (deactivating group): In electrophilic aromatic substitution, an aromatic ring substituent that decreases nucleophilicity and arenium ion

arenium ion
Illustrated Glossary of Organic Chemistry - Arenium ion. Arenium ion: A carbocation formed by electrophilic attack on an aromatic ring. A reactive intermediate in electrophilic aromatic substitution. Formation of an arenium ion by electrophilic attack on benzene.
http://www.chem.ucla.edu › harding › IGOC › arenium_ion
stability (relative to a hydrogen atom), thereby causing the reaction to be slower than the same reaction on benzene itself.

What is activator and deactivator?

Generally speaking, electron donators / activators have a lone pair of electrons or an electron density that “pushes” into the benzene. Electron withdrawers / deactivators have a positive charge on the substituent or a very electronegative atom attached to it, which “pulls” electrons out of the benzene.

What does it mean to be meta directing?

Meta director: In electrophilic aromatic substitution, a substituent that favors electrophilic attack meta to the substituent. Most meta directors are also deactivators.

What is meta directing deactivator?

Deactivators are meta-directing because of the placement of the + charge in the resonance forms of the sigma complex. The meta position becomes more stable because having two + charges next to each other is particularly unstable, as seen in the resonance forms for the ortho and para positions.

Why is meta directing group deactivator?

Halogens are very electronegative. This means that inductively they are electron withdrawing. However, because of their ability to donate a lone pair of electrons in resonance forms, they are activators and ortho/para directing. ... Electron withdrawing groups are meta directors and they are deactivators.

Electrophilic Aromatic Substitution

41 related questions found

Which of the following is meta directing?

Examples of meta– directors include nitriles, carbonyl compounds (such as aldehydes, ketones, and esters), sulfones, electron-deficient alkyl groups, nitro groups, and alkylammoniums. Specific example: nitration of trifluoromethylbenzene gives the meta product in about 90% yield.

What is the most deactivating group?

Hint: The deactivating group is known as the electron-withdrawing group, so the group which can attract electrons towards itself is known as a deactivating group. The group that has the most electronegative atoms will be the most deactivating group.

Is a deactivating group?

If electrophilic aromatic substitution of a monosubstituted benzene is slower than that of benzene under identical conditions, the substituent in the monosubstituted benzene is called a deactivating group. All deactivating groups are electron-withdrawing groups. ...

Is OCH3 activating or deactivating?

Any group with decreases the rate (relative to H) is called adeactivating group. Common activating groups (not a complete list): Alkyl, NH2, NR2, OH, OCH3, SR. Common deactivating groups (not a complete list): NO2, CF3, CN, halogens, COOH, SO3H.

What is meta effect?

The meta effect refers to the community reaction to certain posts here on Meta, in particular posts that point to another post on Stack Overflow. This tends to be a negative effect - people who come to complain/ask about posts on Stack Overflow on Meta are essentially inviting scrutiny and review of these posts.

Is NHCOCH3 Ortho para?

The acetamido group (-NHCOCH3) is an ortho-para directing group in electrophilic aromatic...

What position is meta?

Meta position in organic chemistry is the one in which there are two same functional groups tied to a ring of benzene in position 1 and 3. The abbreviation m- is used, for example, m-Hydroquinone is 1,3-dihydroxybenzene.

What is activator in benzene?

Ring activators are groups that increase the electron density on the benzene ring and thereby make the ring more susceptible to electrophilic aromatic substitution reactions.

Is activating or deactivating group?

If a group increases the stability thereby increases overall reactivity of the electrophilic substitution reaction, then it can be termed as activating group. Similarly if a group reduces the stability of intermediate thereby reduces the reactivity, then it can be termed as deactivating group.

Why is NO2 a deactivating group?

Electron withdrawing groups (EWG) with π bonds to electronegative atoms (e.g. - C=O, -NO2) adjacent to the π system deactivate the aromatic ring by decreasing the electron density on the ring through a resonance withdrawing effect. The resonance only decreases the electron density at the ortho- and para- positions.

Why is oh more activating than OCH3?

OCH3 group is more electron withdrawing (i.e, shows more -I effect) than the OH group. Explanation: The reason is that, there are two lone pairs of oxygen. ... However, in case of OH, the H atom is comparatively much much smaller than O, so here no Steric repulsion takes place.

Is Oh electron donating or withdrawing?

OH is an electron donating group.

Is no2 Ortho para directing?

Since NO2 is an electron withdrawing group, a glance at the resonance structures shows that the positive charge becomes concentrated at the ortho-para positions. Thus these positions are deactivated towards electrophilic aromatic substitution. Hence, NO2 is a meta-director, as we all learned in organic chemistry.

Is BR electron donating or withdrawing?

Bromobenzene is introduced to a carbocation. Bromobenzene will likely react, but at a slower rate than unsubstituted benzene, because the bromine is inductively withdrawing. The bromine is also not resonance donating/activating, but can stabilize the intermediate product through resonance donation.

Is OCH3 ortho para directing?

The aldehyde group is electron-withdrawing and meta-directing. Okay, this one isn't so clear. Both –OCH3 and –Ph are activating, ortho-/para-directing groups.

Is BR ortho para or meta?

Some common ortho para directing groups are –Cl, -Br, -I, -OH, -NH2, -CH3, -C2H5. The group which directs the second incoming group to the meta position, is called a meta-director. For example, alkylation of nitro benzene gives m-alkylnitro benzene as major product.

Is meta a directing group?

1: Thus, the methyl group is an ortho, para directing group. ... Ortho, para directing groups are electron-donating groups; meta directing groups are electron-withdrawing groups. The halide ions, which are electron-withdrawing but ortho, para directing, are the exception.