What would be the three organic products when 2-pentanol reacts with H2SO4 under heat?
Sunday, June 1st, 2008 at
10:06 pm
There are three possible products:
1. Most abundant organic product?
2. Least abundant organic product?
3. Second most abundant organic product?
Someone please help me, and also let me know where to start and how to get this? Thanks
Another similar question:
What would be the major AND minor organic product when 2,6-dimethyl-4-heptanol reacts with H2SO4 with heat?
Tagged with: 2pentanol • H2SO4 • heat • Organic • Products • reacts • three • under • Would
Filed under: Organic Food news
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Alcohols usually dehydrate according to the E1 mechanism.
H+ adds to the hydroxyl group, giving the -[H2O]+ group, which then leaves giving a carbocation with a positive charge in the 2-position. We will assume that no rearrangement takes place, because if it does, then we will get more than 3 products.
A H+ now has to be lost from an adjacent carbon in order to complete the reaction by forming a double bond. If it is lost from the 1-carbon, we will get 1-pentene. If it is lost from the 3-carbon, we will get 2-pentene, but it could be either (E)-2-pentene or (Z)-2-pentene. To determine which, notice that the predominant product forms from the most stable transition state (the carbocation). Free rotation about the 2,3-bond allows the substituents on either side to adopt the most stable anti conformation. Loss of H+ then allows the (E)-isomer to form, so this predominates over the (Z)-isomer, which has to be formed from a less stable conformation of the carbocation. Finally, Zaitsev’s rule predicts that 2-pentene predominates over 1-pentene, since the former has the more highly substituted double bond. The answers are
1. (E)-2-pentene
2. 1-pentene
3. (Z)-2-pentene