Lesson 3 (cyclic cpds, aromatics, & benzene rings)

Question 1

what is the smallest ring shape?

Answer 1

cyclopentane (aka a triangle of carbons), formula: C3H6

Question 2

what prefix is used on parent chains for cyclic compounds?

Answer 2

Cyclo. Ex) cyclohexane

Question 3

What are the 3 types of cyclic compounds?

Answer 3

Cycloalkanes, cycloalkenes, and cycloalkynes

Question 4

What is the restriction on cycloalkynes?

Answer 4

Cycloalkynes do not form unless the ring has more than 10 carbons. (due to the triple bonds sp hybridization and need to stay 180 degrees apart)

Question 5

What is the formula of a benzene ring?

Answer 5

C6H6

Question 6

The formula for a beneze ring is C6H6. What does this suggest?

Describe bonds, what they should be, what they actually are

Answer 6

Theoretically, there should be 3 shorter double bonds and 3 longer bonds. Yet all 6 are the same length. (overall shorter than a single, but longer than a double) Since all C’s are the same distance, each p orbital touch and form one big pi bond called the pi system.

Question 7

What is an aromatic cpd? What characteristics does one need to have for it to be classified as such?

Answer 7

Compounds/molecues with a pi system and delocalized e- are told to be aromaticity. Any compound that has a benzene ring is an aromatic

Question 8

What are the 2 ways benzene can be named?

Give an example

Answer 8

Benzene as a branch: occurs when a higher priority group is present or of the carbon chain is very complex. In this case it’s called phenyl [feen-al]
Benzene as a parent: benzene=parent chain Ex) 1-ethyl-2-flourobenzene