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Problem_set_v_answer - CHEM 302 Organic Chemistry I Problem Set V Chapter 5 Answers 1 The heats of combustion for 2-methylheptane

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CHEM 302 Organic Chemistry I Problem Set V Chapter 5 Answers 1) The heats of combustion for 2-methylheptane, 2,2-dimethylhexane, and 2,2,3,3- tetramethylbutane are 1306.3, 1304.6, and 1303.0 kcal/mole respectively. Construct an energy diagram showing the relative stabilities of these molecules. Basically, this is just a question to help you see how energetics work. For all the given compounds, the molecular formula is: C 8 H 18 , so we have a homologous series of compounds. Therefore, for all of them, the products are the same (same number of moles and everything) so any energy differences have to arise from differences in starting material stability. Here is the balanced equation (although you don’t need it!): C 8 H 18 + 25 / 2 O 2 8CO 2 + 9H 2 O Given all this, here is the diagram as I see it: 2-methylheptane 2,2,-dimethylhexane 2,2,3,3-tetramethylbutane E n e rg y 2) Look down the C(4)-C(3) bond (see figure below) and draw the Newman projection of the chair conformation of methylcyclohexane, where the methyl group is equatorial. H 3 C Well, here we are:
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H H H H 3 C H H 2 C H H H C H 2 Here we can see why the equatorial is more stable—the alkyl groups are anti as opposed to gauche. 3) Draw the most stable chair conformation of the following: a) Real give-away. There is only one chair conformation to consider. As the methyl groups are trans and 1,3, one must be axial and one must be equatorial. Therefore, here is our structure: H 3 C CH 3 H
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This note was uploaded on 04/09/2010 for the course CHEM 302 taught by Professor Myers during the Fall '09 term at Simons Rock.

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Problem_set_v_answer - CHEM 302 Organic Chemistry I Problem Set V Chapter 5 Answers 1 The heats of combustion for 2-methylheptane

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