4.2 Isomerism

Question 1

What are constitutional isomers?

Answer 1

compounds that have the same molecular formula but have their atoms connected together differently

Question 2

What are conformational isomers?

Answer 2

compounds that have the same molecular formula and the same atomic connectivity but differ from one another by rotation about the sigma bond

Question 3

What are the two orientations for saturated hydrocarbons?

Answer 3

staggered and eclipse

Question 4

Which is more stable: staggered or eclipsed?

Answer 4

staggered

Question 5

Why is staggered more stable than eclipsed?

Answer 5

electron repulsion and steric hindrance

Question 6

What is the anti conformation?

Answer 6

staggered conformation that arises when the two largest groups attached to adjacent carbons are 180 degrees apart

Question 7

What is the gauche conformation?

Answer 7

the two largest groups on adjacent carbon atoms are in a staggered conformation 60 degrees apart

Question 8

What is syn conformation?

Answer 8

eclipsed conformation where the two largest groups on adjacent carbon atoms are directly aligned

Question 9

What are the three conformations for cycloalkanes?

Answer 9

envelope
chair model
boat conformation

Question 10

What are the two distinct hydrogens in a chair conformation?

Answer 10

equatorial
axial

Question 11

Which is more favorable: axial or equatorial hydrogrens?

Answer 11

equatorial

Question 12

What are stereoisomers?

Answer 12

molecules that have the same molecular formula and connectivity but differ from one another only in the spatial arrangement of the atoms

Question 13

What does it mean to be chiral?

Answer 13

any molecule that can be superimposed on its mirror image and has a plane of symmetry

Question 14

What does it mean to be achiral?

Answer 14

any molecule that cannot be superimposed on its mirror image

Question 15

What is R configuration?

Answer 15

path is clockwise

Question 16

What is S configuration?

Answer 16

path is counterclockwise

Question 17

What is a Fisher projection?

Answer 17

simplification of the molecules actual three dimensional structure

Question 18

What are enantiomers?

Answer 18

non-superimposable mirror images

Question 19

What is an optically active compound?

Answer 19

compound that rotates the plane of polarized light

Question 20

What is dextrorotatory?

Answer 20

compound that rotates plane of polarized light clockwise

Question 21

What is levorotatory?

Answer 21

compound the rotates plane of light counterclockwise

Question 22

What is a racemic mixture?

Answer 22

equal mixture of a pair of enantiomers; does not rotate plane of polarize light because enantiomers cancel each other out