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Why don't aryl halides undergo nucleophilic substitution reactions?
Wiki User
∙ 10y ago
because the bond between the halogen and the carbon in the benzene ring (aryl halide) or a carbon participating in a double bond (vinylic halide) is much too strong--stronger than that of an alkyl halide--to be broken by a nucleophile (Sn2). Also the electrons of the double bond or benzene ring repel the approach of a nucleophile from the backside. They do not undergo Sn1 reactions because the carbocation intermediate they would produce is unstable and does not readily form.
Wiki User
∙ 14y ago
Wiki User
∙ 14y agoYou cannot do Sn1 or Sn2 on an sp2 center. The reaction only works with sp3 centers. It has to do with the way the LUMO on the electrophile is positioned. A LUMO on an sp3 center is a sigma* antibonding orbital - easily attacked by the lone pair on a nucleophile (which is sigma-like). The LUMO on an sp2 center is a pi* antibonding orbital, which cannot be attacked by a sigma-like orbital.
Wiki User
∙ 10y agoThere is a more rigorous molecular orbital theory argument that can be made why an aryl halide will not do a nucleophilic substitution, but if you just look at the transition state of either the halide leaving (as in SN1) or the nucleophile initiating a backside attack (as in SN2), you can see that both involve unfavorable bond geometry and/or high steric hindrance.
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Why vinyl halide do not undergo nucleophilic substitution?
Lone pair of electron on the halogen atom overlaps with the adjacent pi bond electrons and get delocalised.Therefore halogen atom can't be removed easily. -V.Nandhakumar
Is it possible for an alkyl halide to undergo sn1 and also sn2 reactions?
Yes an alkyl halide can undergo both Sn1 and Sn2 reactions - it just depends on what kind of alkyl halide it is. Methyl halides such as CH3Br/CH3Cl/CH3I, etc. are most suitable for Sn2 reactions because they are less sterically hindered by R-groups (they are not "bulky"). This allows for easy attack by the nucleophile. Primary alkyl halides (RCH2X) are also most suitable for Sn2 because of the same reason above Secondary alkyl halides can undergo both Sn1 and Sn2 reactions, this depends on other factors such as solvent and leaving group and nucleophile. If the solvent is polar aprotic, the reaction will go Sn2, if polar protic - Sn1. Tertiary alkyl halides (alkyl halides with 4 r-groups) do not go Sn2 because they are bulky and the R-groups stabilize the carbocation by hyperconjugation and inductive effect.
What is the test for carbon carbon double bond?
Stick the substance in question into a bromine (or any other halogen) water bath.If a reaction occurs, then there the reagent is an Alkene.This is because the of nucleophilic substitution will happen between the Alkene and Halogen; usually referred to as Halogenation.Alkanes don't undergo Halogenation.
Does methanol react with sulphuric acid?
Alcohols can be protonated by strong acids such as sulfuric acid. This is the reaction scheme (I'm simply representing sulfuric acid as a proton source). CH3OH + H+ ---> CH3OH2+ This protonated methanol species, the methyl oxonium ion, is now a pretty decent electrophile and can undergo a nucleophilic substitution.
Why does sodium and potassium undergo similar reactions with water?
They undergo similar reactions because they are both in the same group on the periodic table.
Why alkyl halides undergoSN reactions or elimination reactins in priority?
Alkyl halides undergo both nucleophilic substituions reactions and Elimination reractions depending upon the conditions...In the presence they undergo Elimination Reactions , while in the presence of nucleophile they undergo SN reactions...By: Farman ullah ,Azim kala, masha mansoor, lakki marwat, kpk,Pakistan+92321-9632344
Why benzene undergo electrophilic substitution reaction easily and nucleophilic substution reaction with difficulty easily and?
the electron in benzene are delocalised making d ring to be elctron rich,thereby undergoing electrophilic substitution.benzene cannot undergo nucleophillic substitution,it can only undergo if it is substituted with an electron withdrawing group
Why tertiary alkyl halides do not undergo wurtz reaction?
The Wurtz reaction is not suitable for tertiary alkyl halides due to side reaction involving elimintaion reactions.
What type of reaction is exhibited by alkenes?
Alkynes undergo many addition reactions such as: catalytic hydrogenation, addition by electrophilic reagents, hydration with tautomerism, hydroboration reactions, and oxidations. They also undergo nucleophilic addition reactions & reduction. Finally alkynes are the strongest bronsted acids made from only hydrocarbons.
Why vinyl halide do not undergo nucleophilic substitution?
Lone pair of electron on the halogen atom overlaps with the adjacent pi bond electrons and get delocalised.Therefore halogen atom can't be removed easily. -V.Nandhakumar
Is it possible for an alkyl halide to undergo sn1 and also sn2 reactions?
Yes an alkyl halide can undergo both Sn1 and Sn2 reactions - it just depends on what kind of alkyl halide it is. Methyl halides such as CH3Br/CH3Cl/CH3I, etc. are most suitable for Sn2 reactions because they are less sterically hindered by R-groups (they are not "bulky"). This allows for easy attack by the nucleophile. Primary alkyl halides (RCH2X) are also most suitable for Sn2 because of the same reason above Secondary alkyl halides can undergo both Sn1 and Sn2 reactions, this depends on other factors such as solvent and leaving group and nucleophile. If the solvent is polar aprotic, the reaction will go Sn2, if polar protic - Sn1. Tertiary alkyl halides (alkyl halides with 4 r-groups) do not go Sn2 because they are bulky and the R-groups stabilize the carbocation by hyperconjugation and inductive effect.
What reaction does aromatics undergo?
Substitution
What is the test for carbon carbon double bond?
Stick the substance in question into a bromine (or any other halogen) water bath.If a reaction occurs, then there the reagent is an Alkene.This is because the of nucleophilic substitution will happen between the Alkene and Halogen; usually referred to as Halogenation.Alkanes don't undergo Halogenation.
Comment Pyridine undergo nucleophilic and electrophilic substitution reaction?
Pyridine will add to carbon 3 in electrophilic reactions, such as Bromine addition. However in a nucleophilic reaction, such as seen in the Chichibabin reaction, carbon #2 and #4 are substituted such as if NH2 - attacked. Draw out the resonance forms and you will see this, or consult any Organic text under heterocyclic Chemistry.In a C3 attack, the electrophile will destabilize the C2 and C4 position, to a great extent since N lacks an octet in one of these resonance forms.In a nucleophilic addition, addition at C2 or C4 allows the negative charge to be shared by Nitrogen thus is preferred to the C3 attack. Hope that helps. Dr Jim Romano CEO Romano Scientific CEO Orgoman.com Class of 1991 NYU
Does methanol react with sulphuric acid?
Alcohols can be protonated by strong acids such as sulfuric acid. This is the reaction scheme (I'm simply representing sulfuric acid as a proton source). CH3OH + H+ ---> CH3OH2+ This protonated methanol species, the methyl oxonium ion, is now a pretty decent electrophile and can undergo a nucleophilic substitution.
Do elements tend to undergo chemical reactions that decrease stability?
Elements tend to undergo chemical reactions that increase stability.
Aryl halide do not undergo SN reaction?
Do not undergo SN1 reactions.
