Chem 12B Objective 5: Understand electrophilic addition reactions of conjugated dienes
In the electrophilic addition of hbr to conjugate dyeing we saw that two products are forming a one-two product and one for plaque so let’s see how temperature affects the product distribution low temperature produces more of the one-two product high temperature produced more than one for product to allylic carbocation intermediates are formed so at low temperature
The more stable carbo cation intermediate forms and that will produce the less stable product and at high temperature the less stable allylic carbocation forms but that will produce the more stable product isoprene reacts with hbr four possible intermediates and products or some so stop the video and determine the temperature at which each product forms so remember
The more stable the intermediates formed at low temperature the less tables formed at high temperature so for the first one that’s giving a low and this will be high and for the other two here are the answers so let’s work backwards to make this allylic bromide which conjugate dying would you start with so stop the video and consider whether you start with a
Or b let’s take a look at the next slide to find out from the previous slide you predicted the products of each reaction at high and low temperature so you can use towards reacting a or b but you use high temperature so if you like lavender you like linda rule now lin rule is an allylic alcohol so stop the video and identify the starting material you would use
To make this compound so you’ll want to start with the conjugate of tiny and react with the hbr and then once you get the alok bromide convert that to the linked alcohol now what you want to use high temperature low temperature conditions stop the video and think about my that force in a second and the answer is well oh temperature draw the allylic carbo cation
Intermediates to convince yourself electrophilic addition of a house until kanji italian tends to form the one for product rather than one to product so this suggests that the bologna mind intermediate has some carbo cation character this is good organic chemistry skills practice so add these dying reactions to our organic reaction map so stop the video and identify
The reaction type and we asked conditions for each reaction so here are the answers so remember to identify these structural features and that will help you determine the reaction type and the reaction conditions
Transcribed from video
Organic Chemistry II: Effect of Temperature on conjugated diene addition reactions By ccchemteach.com
