CHEM301 F09 CA9B

CHEM301 F09 CA9B - CHEM301, Fall 2010 Dr. Ruder 1 Class...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Dr. Ruder 1 Class Activity 9B Substitution Nucleophilic Unimolecular, SN1 Two-step nucleophilic substitution. Model 1 : Two-Step Nucleophilic Substitution (SN1) In a two step substitution reaction (SN1) mechanism, the first step is slow and is the rate determining step, while the second step is fast. Br H 3 C H 3 C H 3 C CH 3 O CH 3 CH 3 CH 3 CH 3 H 3 C CH 3 + Br HOCH 3 H CH 3 O CH 3 CH 3 CH 3 H + SLOW FAST intermediate carbocation SN1 (two-step) mechanism Step 1 Step 2 Step 3 deprotonation Questions 1. For the reaction shown in Model 1 above: (a). What bonds are formed/broken in the first step of the SN1 reaction? (b). What bonds are formed/broken in the second step of the SN1 reaction? (c). Label the nucleophile (Nu-) and the electrophile (E+) and circle the leaving group. (d). Draw curved arrows to show electron movement. (e). Step 3 in Model 1 (deprotonation) involves loss of the proton that was part of the incoming group, to return the oxygen to a neutral charge. Draw curved arrows to illustrate this proton loss. 2. The mechanism for an SN1 reaction occurs in two steps as shown in Model 1: (a). Why do you expect the first step to be slow and the second step to be fast? (b). Which step would be the rate determining step? (c). How many reactants are involved in the rate determining step? (d). Based on your answer to 2c above, explain why the SN1 reaction is unimolecular. (e). The rate equation for an SN1 reaction is Rate = k[CH 3 Br]. Explain how the rate equation supports a unimolecular reaction. 3. Focus on the carbocation intermediate formed in the SN1 mechanism. (a). What is the hybridization of the carbon with the charge? (b). What is the shape of the carbocation structure (tetrahedral, trigonal planar etc)? (c).
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/30/2011 for the course CHEM 301 taught by Professor Sahli during the Spring '07 term at VCU.

Page1 / 5

CHEM301 F09 CA9B - CHEM301, Fall 2010 Dr. Ruder 1 Class...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online