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An SN1 reaction is an unimolecular substitution reaction (hence the name SN1). This means it's a substitution reaction in which the rate of the reaction is only dependent on the concentration of the substrate, as opposed to SN2. In an SN1 reaction, the leaving group of the substrate departs first, leaving a carbocation on the substrate. Then, the nucleophile donates an electron pair to the carbocation and forms a bond. In an SN1 reaction, the carbon molecule bonded to the leaving group must therefore be a tertiary substituted carbon. This is because when the leaving group departs from the molecule, only a tertiary substituted carbon is stable enough as a cation.
Keep in mind that an SN1 reaction leads to two isomer products. If the tertiary carbon is a chiral senter, the two products of the SN1 reaction have an R and S configuration, respectively. The mixture of these isomers is racemic, and the isomers have identical physical properties.
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∙ 7y ago
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∙ 13y agoAn SN1 reaction will occur if:
- The substrate can form a relatively stable carbocation (typically from a tertiary carbon)
- The nucleophile is relatively weak
- A polar protic solvent is used.
An SN2 reaction will occur if:
- The substrate is with a relatively unhindered leaving group (typically from a methyl, primary, or secondary alkyl halide)
- The nucleophile is strong (usually negatively charged) and is of high concentration
- The solvent used is polar and aprotic.
Wiki User
∙ 14y agoSn1 and Sn2 are basically two mechanisms of a reaction taking place.
Sn1 happens in two steps and depends only on ONE of the reactant's concentration while
Sn2 happens in one step and depends on BOTH of the reactant's concentrations...
Sn1 goes by carbocation mechanism while in Sn2 there is a transition state..
For more here are the links :-
http://en.wikipedia.org/wiki/Sn1
http://en.wikipedia.org/wiki/Sn2
Wiki User
∙ 10y agoSN1 is a substitution reaction in organic chemistry. One of the many reactions of SN1 is a reaction taking place with an SN1 reaction mechanism is the hydrolysis of dertbutyl bromide with water forming tert-butanol.
Wiki User
∙ 12y agoSn1 is a unimolecular substitution reaction and is first order. it is a disassociation reaction and depend on one spices concentration. it is favor in poler solvent.
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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 kind of reaction -SN1 or SN2 or E1 or E2- is expected for secondary haloalkanes with sterically hindered strong bases?
the mostly undergo SN1 or E1.. but ratio of E1 is higher...
Are SN1 or SN2 reactions faster?
Depends. SN1 will be faster if: ~Reagent is weak base. ~C connected to the Leaving Group is tertiary (sometimes secondary) ie the leaving group must be a better leaving group. the leaving ability is inversely proportional to the basisity of the compound (its basic character ~The solvent used is polar protic (water and alcohols, etc.) SN2 will be faster if: ~Reagent is a strong base. ~C connected to the LG is primary or a methyl group (sometimes secondary) ~The solvent used is polar aprotic (DMF, DMSO, etc.) ~SN2 reactions need space to inter into the molecule and to push the leaving group thats why the molecule must not be bulky.
Why SN1 and SN2 are dependent on the identity of leaving group?
because these mechanisms works on substitution by one nucleophile from other , as their names. Easier leaving group will faster the reaction.
Why don't aryl halides undergo nucleophilic substitution reactions?
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.
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 role of solvent in nucleophilic substitution reactions?
in sn1 reactions polar solvents are used.why b coz, polar solvent stabilise the intermediate which is formed in the reaction.but in sn2 reactions non polar solvents are used.in this reaction intermediate is not formed.
Predict the two most likely mechanisms which occur when 2-iodohexane is heated in ethanol?
SN2 and SN1
What kind of reaction -SN1 or SN2 or E1 or E2- is expected for secondary haloalkanes with sterically hindered strong bases?
the mostly undergo SN1 or E1.. but ratio of E1 is higher...
What is difference between SN1 and SN2 reaction?
An SN1 reaction will occur if:The substrate can form a relatively stable carbocation (typically from a tertiary carbon)The nucleophile is relatively weakA polar protic solvent is used.An SN2 reaction will occur if:The substrate is with a relatively unhindered leaving group (typically from a methyl, primary, or secondary alkyl halide)The nucleophile is strong (usually negatively charged) and is of high concentrationThe solvent used is polar and aprotic.
Are SN1 or SN2 reactions faster?
Depends. SN1 will be faster if: ~Reagent is weak base. ~C connected to the Leaving Group is tertiary (sometimes secondary) ie the leaving group must be a better leaving group. the leaving ability is inversely proportional to the basisity of the compound (its basic character ~The solvent used is polar protic (water and alcohols, etc.) SN2 will be faster if: ~Reagent is a strong base. ~C connected to the LG is primary or a methyl group (sometimes secondary) ~The solvent used is polar aprotic (DMF, DMSO, etc.) ~SN2 reactions need space to inter into the molecule and to push the leaving group thats why the molecule must not be bulky.
What is the difference between an E1 and a Sn1 reaction?
in sn1 reaction the electrophile leaves the substrate forming a carboncation.afterwards the nucleophile while attack the carboncation and usually recimes may be formed in sn1 reaction depending on whether the carboncation experienced a front of backside attack. in sn2 reaction the departing and attacking proccess occurs at the same time. these is pule rampai from the university of johannesburg
Why SN1 and SN2 are dependent on the identity of leaving group?
because these mechanisms works on substitution by one nucleophile from other , as their names. Easier leaving group will faster the reaction.
Why don't aryl halides undergo nucleophilic substitution reactions?
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.
Why protic slovents favours SN2 reaction and aprotic solventsfavours SN1 reactions?
you have it backwards. SN2: you want a polar APROTIC solvent. Protons are bad because they would solvate (surround) and stabilize the nucleophile, making it less reactive. SN1: you want a polar PROTIC solvent. Protons are good because they will solvate (surround) and stabilize the leaving group as it leaves. This lowers the energy of the transition state and makes the reaction go faster. a final teaching point: recognize that your question essentially is about what makes the reaction go faster, which is a question of KINETICS, NOT THERMODYNAMICS (if you want to be good at orgo, this concept is VERY IMPORTANT). You will make the reaction go faster by stabilizing the transition state of the rate limiting step. The transition state of the rate limiting step in an SN1 reaction is the leaving group leaving (the nucleophile is NOT involved, therefore, it does not matter that it is solvated). That of an SN2 reaction is the nucleophile attacking the carbon center as the leaving group is leaving (the nucleophile IS involved, so it must not be solvated).
Which is more chemically active chloride or Fluoride?
Fluorine gas, the element, is more reactive than the elemental gas chlorine. The ions fluoride and chloride the reactivity depends on the solvents and the reaction mechanism. sn1 vs. sn2.
Account for the behavior of bromobenzene toward I?
A halide ion (I-, Br-, or Cl-) is the most common leaving group of Sn2 reactions
