ORGO Ch. 2 Isomer

Question 1

What is a conformational isomer?

Answer 1

same molecules that differ around the single bond

Question 2

What is gauche staggered conformation?

Answer 2

methyl groups are 60 degrees apart

Question 3

What is eclipse conformation?

Answer 3

methyl groups are 120 degrees apart

Question 4

Which is the least genetically favorable conformation?

Answer 4

totally eclipsed - 2 largest groups are on the same plane on the same side

Question 5

Which is the most genetically favorable conformation?

Answer 5

anti staggered - 2 largest groups are on the same plane but on opposite sides

Question 6

What are the 3 factors that create ring strain?

Answer 6

angle strain, torsional strain, and nonbonded strain/steric

Question 7

What causes angle ring strain?

Answer 7

when bonded angels are stretched or compressed

Question 8

What causes torsional ring strain?

Answer 8

results when cyclic molecules must assume eclipse of gauche conformation

Question 9

What causes nonbonded ring strain?

Answer 9

results when nonadjacent atoms or groups compete for the same space

Question 10

What are the 3 envelope conformations of cyclohexane?

Answer 10

chain, boat, or skew-boat

Question 11

What is the most stable conformation of cyclohexane?

Answer 11

chair conformation

Question 12

What are the 2 configurational isomers?

Answer 12

diastereomers and enantiomers

Question 13

What is the diff b/w diastereomers and enantiomers?

Answer 13

enantiomers are non-superimposable mirror images with opposite stereochemistry at every chiral carbon, diastereomers are not mirrored images of each other with different chemical and physical properties

Question 14

What happens in racemic mixtures?

Answer 14

+ and - enantiomers are presented in equal concentration, thus the rotations cancel each other out, and there is no optical activity observed

Question 15

What is the diff b/w cis and trans isomers?

Answer 15

cis - 2 substituents are on the same side of the immovable bond
trans - 2 substituents are on opposite sides of the immovable bond

Question 16

What are the criteria for a molecule to have optical activity?

Answer 16

they must have a chiral center, and lack a plane of symmetry

Question 17

What is a mesocompound?

Answer 17

a molecule with chiral centers that has an internal plane of symmetry

Question 18

How is priority in E and Z determined?

Answer 18

priority is assigned based on the atom bonded to the double bond; the higher the atomic number, the higher the priority

Question 19

What is the diff b/w E and Z forms?

Answer 19

The alkene is named Z if the 2 highest priority substituents on each carbon are on the same side of the double bond, and E if they are on opposite sides

Question 20

What is the diff b/w R and S forms?

Answer 20

R = clockwise - right turn from highest to lowest priority
S = counterclockwise - left turn from highest to lowest priority molecule

Question 21

In Fischer’s projections, what is the direction of the lowest priority group?

Answer 21

the lowest priority groups project in to the page

Question 22

What is anti-staggered conformation?

Answer 22

methyl groups are 180 degrees apart

Question 23

What position creates less strain in a cyclohexane molecule?

Answer 23

equatorial