Question

draw and label all relevang conformations.

2. Draw and label all relevant conformations (Newman projections) for 1-chior 2,2,2-tribromoethane. Also, identify the dihedral angle between pertinent substituents. Finally, draw a graph of relative energy vs. dihedral angle for 2,2,2-tribromoethane. (14 points) 3. Draw the most stable conformations for cis-1,4-dimethylcyclohexane and trans-1,4 dimethylcyclohexane and explain which geometric isomer is lower in energy. (12 points) 4. Using the CA-Cs bond axis as a reference, draw and label all relevant conformations (Newman projections) for octane. Also, identify the dihedral angle between the pertinent substituents on C4 and C5. Finally, draw a graph of relative energy vs. dihedral angle for octane. (24 points)

Answer 1

# To answer this que non, let draw the ette - e - By g n dimensionat i me CRM shall look as a In Newmann, this conformation the first write o let us 12. To answer this structure Charco il BY Stact with the projection; we can In Newmann con former : BY H +600 H dinedral angle (da halamat) anti) (ecclipsed) Tv lanti) ( ecclipsed) HHH 1999

If we look we look at the conformers, a, u are identical, I o are identical ; D jy one identical Homes, we Con all consider only the following conformes for dihedral angle to discussion dinedral BY angle a boo v ondu waal interace Now; the stere strain y vanderwaal interaction Thus, the profile is a Energy 0 60 - 120 180 200 300 360 along Dinedral anglelo) between erhedral angleloj bawean calq axis 13. Cis-1-4, dimethyl ey do hexane is trans - Igu, dimethyl ey do hexane is stability However, as can be predicted only if we construct structures in boat form, on 1, bulky methye group is in axial position in at c-u for us. Hence, di axial e interaction thau increase energy. trans- both groups are in equitorial position Thus, it is lower in energy

for octane; the structure in structure as reference, the aring cocco axis саn bе ол ее, а л of the Cz Hq - CH2 - CH₂ - Cz Hz the Newmann projection formulal us; CHA conformations are in 3 H7 @ 1206 o= dihedral angle IH H aHa 200 B C₂ HA 0 - 3000 A = 180° two i A ecclipsed interaction between C₃ Hq groups is greater in energy than staggered interactions, the energies of the conformere are : 1 > > > IV [::DX @ 207 Energy 0 60 120 180 200 300