Isomers

Question 1

What is a constitutional isomer?

Answer 1

• Different nature/sequence of bonds.

Question 2

What is an isomer?

Answer 2

• Isomers are molecules with the same molecular formula, but differnt structures

Question 3

• Define the term stereoisomer and name the types of stereoisomers.

Answer 3

• A stereoisomer is an isomer which has the same nature/sequence of bonds (connectivity) but different orientations of their atoms in space.
• There are two types
  
  • Configurational
  • Conformational

Question 4

What is a configurational isomer?

Answer 4

• A configurational isomer is one where interconversion requires breaking and remaking bonds
• They cannot be interconverted by rotation about a single bond
• Not normally separable at room temperature

Question 5

What is a conformational isomer?

Answer 5

• Isomers which differ by a rotation about a single C-C bond.
• not normally separable at room temperature.

Question 6

What are Enantiomers?

Answer 6

• Enantiomers are a pair of configurational stereoisomers that are non-superimposable mirror images of each other.

Question 7

What types of bond is a double bond made of?

Answer 7

• A double bond is made of both sigma and pi bonds
• Pi-bonds result from p-orbital overlap and are directional

Question 8

What is a diastereomer (diastereoisomer)?

Name the types

Answer 8

• A pair of configurational stereoisomers that aren’t mirror images of each other.
• both ends of the c=c bonds must have 2 different groups
• There are Z and E stereoisomers

Question 9

What is a Z diastereisomer?

Answer 9

• It’s a diastereisomer where the high priority groups are on the same side of the C=C bond
• (on Zee zame zide)

Question 10

What is an E diastereoisomer

Answer 10

• It’s a diastereoisomer where the high priority groups are on the opposite side of the C=C bond

Question 11

What is the difference between cis and trans?

Answer 11

• A cis isomer is a stereoisomer (Z) in which two groups lie on the same side of a reference plane
• A trans isomer is a stereoisomer (E) in which two groups lie on different sides of a reference plane

Question 12

What are the 2 methods used to represent a conformational isomer?

Answer 12

• Sawhorse representation
• Newman’s representation

Question 13

What is the sawhorse representation?

Answer 13

• It is a represenation of the conformational isomer

Question 14

What are the two types of Newman’s representation?
Which has the most energy?

Answer 14

• There is the staggered and eclipsed
• The Eclipsed has the most energy

Question 15

What are the rules to label diastereisomers?

Answer 15

1. Assign priority to each group on each C=C
   
   • The higher the atomic number of the group attached, the higher the priority.
   • If atoms are identical, work along the chain until the first point of difference, then go by atomic number
2. If high priority groups are on the same side of the C=C bond, then it is a Z diastereisomer (on zee zame zide)
3. If priority groups are on opposite sides of the C=C bond, then it is a E diasterisomer