AAMC Sample Test C/P Section Questions *spoilers*

[redraincoat13]

Hey for anyone who already took the sample test, could you please explain C/P #39 and #56 please?

#38 - says mevalonic acid (on the right of the equation) will equilibrate with another structure

can someone explain why mevalonic acid will form a six membered ring with only three oxygens rather than the 4 ester ring with all 4 oxygens? How does the alcohol attack to get rid of one of the O's. And if it does, how can it be in equilibrium with mevalonic acid?

#56 - this is just a math problem but 30 W in 3 mins, calculate work. P =W/t, so W = Pt = 30*3*60 = 540J. Answer says 5400J. Did I miss something or is this a mistake?

Thanks everyone!!!

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[baggins825]

For #39, the 6 membered ring is much more favored because it has much less steric hinderance compared to the 4 membered ring. The mechanism appears to be through a dehydration reaction which involves the removal of H2O

For # 56, you miscalculated 30*3*60 is 5400, not 540.

 

[redraincoat13]

thanks! so in equilibrium with doesn't mean a resonance form but rather another reaction's product?