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Lecture 4

Lecture 4. In chain form, 6 gauche butane interactions ( units). In boat form, 4 gauche butane interactions (units) + 2 eclipsed butane interactions (units) + Bowsprit – Flagpole interaction. E boat -  E chain

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Lecture 4

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  1. Lecture 4

  2. In chain form, 6 gauche butane interactions ( units) In boat form, 4 gauche butane interactions (units) + 2 eclipsed butane interactions (units) + Bowsprit – Flagpole interaction. • E boat -  E chain == ( 2 eclipsed butane – 2 gauche butane) + B.F. Interaction == 2 * 4.0 - 2* 0.9 + B.F. Interaction == 6.2 + B.F. Interaction

  3. Drawing the preferred conformations of cyclohexane derivatives : Cis – 4-t-butyl cyclohexan-1-ol Trans – 4-t-butyl cyclohexan-1-ol Steps : (1) for cis both groups should be a or b for trans one group is a and the other b (2) Now draw the cyclohexane chair : (3) Place the bigger group in the equatorial position. (4) Place the other group axial or equatorial according to cis or trans

  4. Cis and Trans 1,2 – Dimethylcyclohexane : A is the flipped form of B and vice versa. C is the mirror image of B C is same as A A & B are of same energy, so they are present as 50 : 50 mixture and are interconvertible through a low energy barrier. Thus, cis 1,2 – dimethylcyclohexane exists as a nonresolvable dl – pair.

  5. Trans 1,2- dimethylcyclohexane A & C are different. Qn : Draw the preferred conformations of cis and trans 1,3 – dimethyl cyclohexane. Comment on it optical activity.

  6. Qn: Write down the preferred conformations of cis and trans 4-t-butyl-cyclohexan-1-ol. Which compound will undergo faster oxidation to the corresponding ketone with chromic acid? Qn: Assign R/S configuration to the following molecule. Qn. Convert the following Newman Projection into Fischer Projection Formula and then assign R/S.

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