Chemistry Assignment - Carbon-carbon Double Bond

1. Carbon-carbon double bond does not rotate freely as carbon-carbon single bond. Why? (3 points) Because the π bond is a rigid plane and can’t rotate. You’d need to break the p orbital interactions on either side of the molecule before rotating it. The pi bond part of the double bond required shoulder-to-shoulder overlap of the unhybridized p orbitals. Rotation of the double bond will weaken, or even break the p-p overlap. 2. Draw the structure of (Z)-2-penten-1-ol. (3 points) 3. Dehydration of 2-methyl-2-pentanol forms one major and one minor organic product. Draw the structures, including hydrogen atoms, of the two organic products of this reaction. (3 points) 4. What product(s) are expected in the ethoxide-promoted β-elimination reaction of 2-bromo-2,3-dimethylbutane? Omit ions, salts, and ethanol from your response. (3 points) Shouldn’t there be another 1? -1 5. Draw the structure of an alkyl halide that could be used to react with KOC(CH3)3 to give 4-methylcyclohexene as the only alkene product. Using curved arrows to explain the mechanism of this reaction. Name this reaction mechanism. (6 points) Dehydrohalogenation of - OC(CH3)3 produces -3 Draw the char conformation of the cis isomer. See Question # 9. Should be E2. 6. Draw the major organic products of the reaction between cis-2methylcyclohexanol and 85% phosphoric acid (H3PO4) at 170 oC. (6 points) 7. Which of the following C6H12 isomers has the highest heat of combustion? ( (3 points) (a) 1-hexene (b) trans-3-hexene (c) cis-3-hexene (d) 2-methyl-2-pentene A, since it is the least substituted and not branched. ) 8. Which of the following carbocations is (are) likely to undergo a rearrangement? (3 points) All 3 will at least attempt to displace the electron deficiency, considering that II and III are secondary carbocations and I is a primary carbocation, but the only one with a more stable rearrangement is II, where one of the methyl groups would move to the electron deficient carbon, causing the carbon which currently has all three methyls, and a quaternary structure, to become a tertiary cation, which is more stable. 9. Which of the following could have the fastest rate of reaction to form 4-tbutylcyclohexene? (3 points) The rates of reaction are as followed from fastest to slowest: D>C > B>A, since Br reacts faster than Cl and the cis conformation is 500x faster than the trans. Anti elimination: beta-H’s are all anti to Br in the cis compound, which none is in the trans isomer. 10. Consider all possible migrations that might occur to the electron-deficient carbon of the carbocation shown below. Use the curved-arrow formalism to show these migrations, and draw the structures of the rearranged carbocations. Consider only those primary rearrangements, those rearrangements directly involving the skeleton and charge location as shown in the structure. (Secondary and following rearrangements would involve a significantly larger number of possible structures.) Which of these primary rearranged carbocation structures would you expect to be the major component of an equilibrium mixture of all of these carbocations? (4points) The top line of structures would be in relatively similar amounts, all of which producing a secondary carbocation, which is more stable than the primary carbocation found in the second line of structures. -2 Hydride shift to create the tertiary carbocation is the main one. 11. Which alcohol is dehydrated fastest in concentrated H2SO4? (3 points) A, since it is a tertiary alcohol and thus forms the most stable cation when leaving which makes it the quickest to eject its hydroxyl group.