Conformational Analysis and Stereoelectronic Effects

Question 1

Draw the different intermediates which take place during ring flip.

Answer 1

Question 2

Why does cyclohexane never pass through true boat?

Answer 2

Very sterically hindered.

Question 3

Why are 1,3 diaxial repulsions stronger than any repulsion caused by equatorial positions?

Answer 3

Question 4

What is the orbital explanation for the anomeric effect?

Answer 4

Question 5

Of cis/trans decalin, which can ring flip?

Draw ring flips in each case

Answer 5

cis can RF

trans cannot

Question 6

Draw the explanation for E2 reactions using orbital interactions

Answer 6

Note that APP conformation required

Question 7

Draw the explanation for Sn2 reactions using orbital interactions

Answer 7

Question 8

Explain the anomeric effect using orbital interactions.

Answer 8

Question 9

Explain baldwins rules of ring closure classifications

Answer 9

N- exo/endo - dig/trig/tet

N - size of ring formation

exo/endo - bond broken outside or einside ring

dig/trig/tet - geometry

Question 10

What are baldwins rules of ring formation for n-exo classifications?

Answer 10

As a rule of thumb all exo rxns favored

Exceptions: 3-exo-dig and 4-exo-dig

If you look at examples you’ll see that strain in such a reaction is huge

Question 11

What are baldwins rules of ring formation for n-endo classifications?

Answer 11

As a general rule of thumb all endo reactions are disvafored

Exceptions: all dig reactions

6-endo-trig and 7-endo-trig

Question 12

Explain the reaction where a ketone is formed

Answer 12

Question 13

Explain the reaction containing a c-c bond shift

Answer 13