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Althought epoxides do not contain a good...

Althought epoxides do not contain a good leaving group, they contains a strained three membered ring with polar bonds. Nucleophilic attack opens the strained three membered ring making it favorable process even with the poor leaving group.

This reaction occurs readily with strong nucleophilic , and with acids like HZ, where Z is nucleophilic atom.

Find out the correct product of the reaction

A

B

C

D

Text Solution

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The correct Answer is:
B
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Attack by a strong nucleophile such as CH_(3)O^(Theta) (Methoxide ion ) on an epoxide occurs at the least hindered carbon similar to an S_(N)2 reaction Attack by a weak nucleophile such as MeOH . Can occur only when the epoxide has been protonated so that a better leaving group is formed under acidic condition weak nucleophile attacks more substituted carbon to give final product . What would be the major product of the given transformation ?

For a typical nucleophilic aromatic subsitution reaction to take place. (1) Nucleophilic atom should be of oxygen, nitrogen or sulphur. (2) Leaving group should be halide . (3) There should be strong electron withdarwing at ortho and para position to leaving group. Find out correct product of following reaction :

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  • Althought epoxides do not contain a good leaving group, they contains a strained three membered ring with polar bonds. Nucleophilic attack opens the strained three membered ring making it favorable process even with the poor leaving group. This reaction occurs readily with strong nucleophilic , and with acids like HZ, where Z is nucleophilic atom. Find out major product of reaction:

    A
    B
    C
    D
    None of these

  • Althought epoxides do not contain a good leaving group, they contains a strained three membered ring with polar bonds. Nucleophilic attack opens the strained three membered ring making it favorable process even with the poor leaving group. This reaction occurs readily with strong nucleophilic , and with acids like HZ, where Z is nucleophilic atom. What would be the major product of reaction?

    A
    B
    C
    D

  • For a typical nucleophilic aromatic substitution reaction to take place . 1. Nucleophilic atom should be of oxygen nitrogen or sulphur. 2. Leaving groups should be halide. 3. There should be strong electron withdrawing at ortho and para position to leaving group. Find out correct product of following reaction

    A
    B
    C
    D

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    Ring-opening reactions of epoxides can proceed by either S_(N)2 or S_(N)1 mechanisms, depending on the nature of the epoxide and on the reaction conditions. If the epoxide is asymmetric, the structure of the product will very according to which mechanisms dominates. When an symmetric epoxide undergoes solvolysis in basic methanol, ring-opening occurs by and S_(N)2 mechanisms, and the less subsitution carbon is the site of nucleophilic attack. Conversely, when solvolysis occurs in acidic methanol, the reaction occurs by a mechanisms with substantial S_(N)1 character, and the more substituted carbon is the site of attack. These are both good examples of regioselective reactions, examine the basic, S_(N)2 case first. The leaving group is an alkoxide anion, because there i s not acid avaialble to protonate the oxygen prior to ring opening. An alkoxide is a poor leaving group, and thus the ring is unlikely to open without a'push' from the nucleophile. Like in other S_(N)2 reactions, nucleophilic attack takes place from the backside, resulting in inversion t the electrophilic carbon. The best way to depict the acid-catalyzed epoxide ring-opening reaction is as a hybrid, or cross, between an S_(N)2 and S_(N)1 mechanism. First, the oxygen is protonated, creating a good leaving group. Then the carbon-oxygen bond begins to break and positive charge begins to build up on the more substituted carbon. answer the following based on the above : The product formed after nucleophilic attack and mild hydrolysis is

    Ring-opening reactions of epoxides can proceed by either S_(N)2 or S_(N)1 mechanisms, depending on the nature of the epoxide and on the reaction conditions. If the epoxide is asymmetric, the structure of the product will very according to which mechanisms dominates. When an symmetric epoxide undergoes solvolysis in basic methanol, ring-opening occurs by and S_(N)2 mechanisms, and the less subsitution carbon is the site of nucleophilic attack. Conversely, when solvolysis occurs in acidic methanol, the reaction occurs by a mechanisms with substantial S_(N)1 character, and the more substituted carbon is the site of attack. These are both good examples of regioselective reactions, examine the basic, S_(N)2 case first. The leaving group is an alkoxide anion, because there i s not acid avaialble to protonate the oxygen prior to ring opening. An alkoxide is a poor leaving group, and thus the ring is unlikely to open without a'push' from the nucleophile. Like in other S_(N)2 reactions, nucleophilic attack takes place from the backside, resulting in inversion t the electrophilic carbon. The best way to depict the acid-catalyzed epoxide ring-opening reaction is as a hybrid, or cross, between an S_(N)2 and S_(N)1 mechanism. First, the oxygen is protonated, creating a good leaving group. Then the carbon-oxygen bond begins to break and positive charge begins to build up on the more substituted carbon. answer the following based on the above :

    Aromatic hydrocarbons are highly unsaturated molecules but behave like saturated hydrocarbons. Those which contain a benzene ring are called benzenoids but those which contain some highly unsaturated ring other than benzene are called non-benzenoids. Their aromatic character can be ascertained through Hückel rule. Aromatic hydrocarbons are, however, more reactive than alkanes but are less reactive than alkenes and alkynes. The lower reactivity of arenes is because of the extra stability associated with these molecules due to delocalization of -electrons. Their stability is measured in terms of resonance energy which can be estimated from either heat of combustion or heat of hydrogenation data. They normally undergo electrophilic substitution reactions. In presence of a Lewis acid catalyst, nuclear halogenation occurs but in absence of Lewis acid catalyst and in presence of light, halogens add to the benzene ring. If an aromatic hydrocarbon contains an alkyl side chain, then in presence of heat/light side chain halogenation occurs in preference to addition of halogens to the benzene ring. The reactivity of aromatic hydrocarbons towards electrophilic substitution reactions depends upon the electron density in the benzene ring. Electron-donating groups favour while electron-withdrawing groups retard these reactions. Orientation of electrophilic substitution reactions is governed by the nature of the substituent already present in the ring. Although aromatic hydrocarbons are resistant to oxidising agents (KMnO_4, K_2Cr_2O_7 , etc.) they do undergo ozonolysis. In the reaction of C_6H_5Y , the major product ( gt 60%) is m-isomer , so the group Y is

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