8.2 Alkenes in Nature and in Industry

What are alkenes also called?

Olefins

What structural forms can alkenes appear in?

Acyclic, cyclic, bicyclic, or polycyclic

What are acyclic alkenes?

Alkenes that do not contain a ring.

Why are alkenes abundant in nature?

Many natural molecules contain carbon–carbon double bonds.

Where are double bonds commonly found in biological molecules?

In pheromones

What are pheromones?

Chemicals organisms use to trigger behavioral responses in members of the same species.

What is the function of alarm pheromones?

To signal danger.

What is the function of sex pheromones?

To attract the opposite sex for mating

What are terpenes?

Naturally occurring alkenes built from 5-carbon units

Why is the number of carbons in a terpene divisible by 5?

Because they are assembled from 5-carbon building blocks

Where are terpenes commonly found?

Essential oils of plants, including cannabis.

What properties do many terpenes have?

Anti-inflammatory, antibacterial, and pain-relieving effects

Examples of terpenes

Beta-carotene and beta-farnesene

Why are alkenes important in industry?

They are key precursors for many chemical products.

What are the two most important industrial alkenes?

Ethylene and propylene.

How are ethylene and propylene produced?

By cracking petroleum.

How much ethylene is produced yearly?

Over 200 billion pounds

How much propylene is produced yearly?

About 70 billion pounds.

What major materials come from industrial alkenes like ethylene and propylene?

Polymers such as polyethylene, polypropylene, and PVC.

What does (CH₂CHCl)ₙ represent in PVC?

The repeating unit of the polymer, with n being a very large number.