Define saytzeff's rule. give example
Answers
What Are Elimination Reactions?
On a last minute trip to the beach, you pick up a cooler at the grocery store. Made of fluffy, white Styrofoam, it's sure to keep your drinks cool for the day. You bag your groceries in convenient plastic bags and head out. Have you ever wondered how these modern miracles are made? Styrofoam, plastic, and many other common materials are made from alkenes.
Alkenes are hydrocarbon chains with at least one double bond. Chemists synthesize all sorts of different alkenes for different purposes, such as insulation, packaging, manufacturing and fuel. To do this, they use a chemical reaction called an elimination reaction. In this reaction, a hydrocarbon chain has two substituents leave the molecule and the electrons are converted into a double bond between carbon atoms.
Zaitsev's Rule
During elimination reactions, often there is more than one place that a double bond can be formed around the leaving group. Let's look at an example. Say you treat 2,2-bromo-methyl-pentane with a strong acid, which will result in an elimination reaction. Clearly the bromide ion will leave, but will the double bond form between the methyl group and the main chain carbon, or within the main chain carbons themselves?
When this reaction is carried out, the overwhelming product is 2,2 methyl-pentene. The double bond forms between the carbons in the main chain, not the methyl groups. Other reactions produce similar results.
Let's say you combined 1,1 chloro-methyl-benzene with a strong base and heat to carry out an elimination reaction. Will the double bond form within the ring or with the methyl group? Again, most of the product will have a double bond within the ring.
As it turns out, elimination reactions tend to produce products where the double bond creates the most highly substituted alkene. But, like all things in chemistry, this isn't just for looks. There's a good reason why alkenes with more substituents are the greater product.
More highly substituted alkenes tend to be more thermodynamically stable compared to less substituted alkenes. This process was observed and reported by a Russian scientist, Alexander Zaitsev, in the 19th century. Today, we refer to this as Zaitsev's rule, which states that the more highly substituted alkene is the more likely product of an elimination reaction. Thus tetra substituted alkenes are more stable compared to tri-substituted, compared to di-substituted, compared to mono-substituted alkenes
