Which of the following phreases are not correvlty associated with `S_(N^(1))` reaction ?
(I) Rearrangement is possible
(II) Rate si affected by polarity of solvent
(III) the strength of the nuclephile is important in determining rate
(IV) the reacityity series is tertiary gt secondary gt promany
(V) proceeds with complete inversion of configguation
Which of the following phreases are not correvlty associated with `S_(N^(1))` reaction ?
(I) Rearrangement is possible
(II) Rate si affected by polarity of solvent
(III) the strength of the nuclephile is important in determining rate
(IV) the reacityity series is tertiary gt secondary gt promany
(V) proceeds with complete inversion of configguation
(I) Rearrangement is possible
(II) Rate si affected by polarity of solvent
(III) the strength of the nuclephile is important in determining rate
(IV) the reacityity series is tertiary gt secondary gt promany
(V) proceeds with complete inversion of configguation
A
3,5
B
5 only
C
2,3,5
D
3 only
Text Solution
Verified by Experts
The correct Answer is:
a
(a) Informative quwestion .
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Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) S_(N)^(1) mechanism is favoured in which of the following solvents:
Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) S_(N)^(1) reaction will be fastest in which of the following solvents?
Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) Polar solvents make the reaction faster as they:
Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) S_(N)^(1) reaction will be fastest in case of:
Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) Nucleophilic substitution will be fastest in case of:
The high reactivity of alkyl halides can be explained in tems of nature of C-X bond which is highly polarised covalent bond due to large difference in the electronegativities of carbon and halogen atom. This polarity is responsible for the nucleophilic substitution reaction of alkyl halides which mostly occur by S_(N^(1)) and S_(N^(2)) mechanisms. S_(N^(1)) reaction is a two step process and in the first step R-X ionises to give carbocation (slow process). In the second step the nucleophilic attacks the carbocation from either side to form the prodcut (fast process) . In S_(N^(1)) reaction there can be reacemization and inversion . S_(N^(1)) reaction is favoured by heavy (bulky) groups on the carbon atom attached to halogens. i.e., R_(3)C-Xgt R_(2)CH-Xgt R_CH_(2)X gt CH_(3)X. " In " S_(N^(2)) reaction the strong nucleophilie OH^(-) attacks from the opposite side of the chlorine atom to give an inyermediate (transition state). which breaks to yield the product (alcohol) and leaving (X^(-)) group. The alcohol has a configuration opposite to that of the bromide and is said to proceed with inversion of configuration. S_(N^(2)) reaction is favoured by small groups on the carbon atom attached to halogen i.e., CH_(3)-X gt R-CH_(2)X gt R_(2) CHX gt R_(3) C-X Which among the following will not give S_(N^(1)) reaction?
The high reactivity of alkyl halides can be explained in tems of nature of C-X bond which is highly polarised covalent bond due to large difference in the electronegativities of carbon and halogen atom. This polarity is responsible for the nucleophilic substitution reaction of alkyl halides which mostly occur by S_(N^(1)) and S_(N^(2)) mechanisms. S_(N^(1)) reaction is a two step process and in the first step R-X ionises to give carbocation (slow process). In the second step the nucleophilic attacks the carbocation from either side to form the prodcut (fast process) . In S_(N^(1)) reaction there can be reacemization and inversion . S_(N^(1)) reaction is favoured by heavy (bulky) groups on the carbon atom attached to halogens. i.e., R_(3)C-Xgt R_(2)CH-Xgt R_CH_(2)X gt CH_(3)X. " In " S_(N^(2)) reaction the strong nucleophilie OH^(-) attacks from the opposite side of the chlorine atom to give an inyermediate (transition state). which breaks to yield the product (alcohol) and leaving (X^(-)) group. The alcohol has a configuration opposite to that of the bromide and is said to proceed with inversion of configuration. S_(N^(2)) reaction is favoured by small groups on the carbon atom attached to halogen i.e., CH_(3)-X gt R-CH_(2)X gt R_(2) CHX gt R_(3) C-X S_(N^(1)) reaction of optically active alkyl halide leads to :
The reaction 2AX(g)+2B_(2)(g)rarr A_(2)(g)+2B_(2)X(g) has been studied kinetically and on the baiss of the rate law following mechanism has been proposed. I. 2A X hArr A_(2)X_(2) " " ("fast and reverse") II. A_(2)X_(2)+B_(2)rarrA_(2)X+B_(2)X III. A_(2)X+B_(2)rarrA_(2)+B_(2)X where all the reaction intermediates are gases under ordinary condition. form the above mechanism in which the steps (elementary) differ conisderably in their rates, the rate law is derived uisng the principle that the slowest step is the rate-determining step (RDS) and the rate of any step varies as the Product of the molar concentrations of each reacting speacting species raised to the power equal to their respective stoichiometric coefficients (law of mass action). If a reacting species is solid or pure liquid, its active mass, i.e., molar concentration is taken to be unity, the standard state. In qrder to find out the final rate law of the reaction, the concentration of any intermediate appearing in the rate law of the RDS is substituted in terms of the concentration of the reactant(s) by means of the law of mass action applied on equilibrium step. Let the equilibrium constant of Step I be 2xx10^(-3) mol^(-1) L and the rate constants for the formation of A_(2)X and A_(2) in Step II and III are 3.0xx10^(-2) mol^(-1) L min^(-1) and 1xx10^(3) mol^(-1) L min^(-1) (all data at 25^(@)C) , then what is the overall rate constant (mol^(-2) L^(2) min^(-1)) of the consumption of B_(2) ?