Common pitfalls
Solution
Key concepts
) is found to be +2.5, does the reaction involve the buildup of positive or negative charge in the transition state? Explain the physical significance of this value. advanced organic chemistry practice problems
The two terminal methyl groups point in opposite relative directions (one "in", one "out") in the required conformation.
It attacks one of the carbons of the strained epoxide ring, opening it. This second standard SN2S sub N end-sub 2 attack causes a second inversion of configuration. : Two successive inversions (
Disconnect the cyclobutane ring into two alkene fragments. Consider how the substitution pattern on the starting materials will dictate the regiochemistry of the [2+2] addition. Problem 5: Sharpless Asymmetric Epoxidation (SAE) The Challenge: Common pitfalls Solution Key concepts ) is found
React benzene with NBS or bromine under light to form bromobenzene (if starting from alkyl benzenes) or perform a Friedel-Crafts alkylation. Alternatively, brominate toluene to get benzyl bromide. Convert benzyl bromide into a Grignard reagent ( PhCH2MgBrcap P h cap C cap H sub 2 cap M g cap B r
: You must evaluate 1,3-diaxial interactions and A-values to determine the lowest-energy chair conformation.
: Each problem is linked to a specific peer-reviewed article. To solve the "bonus" portion of the problem, the student must navigate the literature to find a specific reagent or condition not explicitly mentioned in the text. Example Practice Scenarios It attacks one of the carbons of the
Determine the R/S configuration for all chiral centers in the following molecule: (2R,3S)-2-bromo-3-chlorobutane. Draw the Fischer projection and the sawhorse projection looking down the C2-C3 bond.
Look for bonds near heteroatoms or carbonyls. Use strategic disconnections that lead to known, stable precursors. 2. Practice Problems: Mechanisms and Product Prediction Problem 1: Regioselective Rearrangement