- Do the following Complete the following table for recording data/observations
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Question
- Do the following
Complete the following table for recording data/observations (10 pts): Part I: Sv1 Reaction: Alkyl halides treated with AgNO3 in ethanol: Name of | Draw substrate structure and label each as Leaving Precipitate substrate (l®, 2, 3, sp2) group | Write Y for Yes, N for No Cl | Immediate: 1-chlorobutane 5 minutes: with heat Cl |Immediate: Cl 5 minutes: 2-chlorobutane Cl | Immediate: Y 2-Chloro-2- 5 minutes: methylpropane with heat Cl Immediate: 3-Chlor°propene 5 minutes: With heat: Y Immediate: Br 5 minutes: With heat Y Immediate: Cl 5 minutes: Chlorobenzene sp2 5 minutes: no reaction PartlliSs2Reaction: Alkyl halides treated with Nal in acetone: Name of Draw substrate structure and label each as Leaving Precipitate substrate ( 1®, 27, 30, sp") group | Write Y for Yes, N for No Immediate: 1-chlorobutane 5 minutes: Immediate: 2-chlorobutane Cl 5 minutes: with heat Y immediate: 2-Chloro-2 Cl 15 minutes: methylpropane With heat: Y Immediate: Y 3-Chlor°propene Cl 5 minutes: Immediate 2-Brom°butane Br 15 minutes: with heat: Y Immediate: Chlorobenzene sp2 CI 15minutes: With heat: Y Copyright ASU Tempe -Dr. Bhushaa,K. Page 2014Explanation / Answer
1. In SN1 reaction carbocation is formed and it is stabilized by +R or +I effect of the nearby groups. Also, it is solvated by solvent ions. Thus in polar solvent SN1 reaction is feavoured. To make nucleophile attack at carbocation it needs to overcome the energy barrier of solvated carbocation. Which is not the case in SN2 reaction. SN2 reaction goes through one transition state and this transition state is not solvated. Hence, SN1 reaction requires more heating as compared to SN2.
2. AgNO3 (in EtOH) gives pramotes ionization of C-Br bond. And hence it gives SN1 product with alkyl halide. Thus, reactivity sequence would be:
1) 3º-alkyl halides, > 2) 2º-alkyl halides, > 3) 1º-alkyl halides
3. As discussed in above example, AgNO3 forms bond with halogen from alkyl halide. Thus the factros such as inductive effect and resonance effect which supports this polarization and then formation of carbo cation will support the rate of reaction to increase. In
3º-alkyl halides there are 3 alkyl groups which has + I effect on carbocation and it pramotes the polarization of C-Br bond by pushing the electron density towards the carbon of C-X. This effect dicreases in 2º-alkyl halides, and then 1º-alkyl halides. Thus the rate of reaction will be fastest in 3º-alkyl halides, then in 2º-alkyl halides, and slowest in 1º-alkyl halides.
4. Alkyl halides with NaI in acetone reacts in SN2 pathway. Thus, reactivity rates in alkyl halides are :
1) 1º-alkyl halides, > 2) 2º-alkyl halides, > 3) 3º-alkyl halides
1º-alkyl halides is the fastest because there is no much steric hinderance for I- to attack from back side of C-x bond in 1º-alkyl halides. Whereas, in 3º-alkyl halides there is a steric hinderance for I- to attack from back side of C-x bond.
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