Chemistry - The Alkenes and the Alkynes

What are the family of alkenes ?

Unsaturated hydrocarbons

What is an unsaturated compound ?

A compound that contains at least one double or triple bond between the atoms in the molecule

What do all alkenes contain ?

A carbon-carbon double bond

What is the general formula for alkenes ?

C_nH_2n

What are structural isomers ?

Molecules that have the same molecular formula, but different expanded molecular formula

Why are alkenes more reactive than alkanes ?

They have a double bond which is a region of high electron density

This electron rich double bond allows alkenes to polarise other molecules and attract electrophiles

What are the family of alkynes ?

Unsaturated hydrocarbons

What do all alkynes contain ?

A carbon-carbon triple bond

What is the general formula for alkynes ?

C_nH_2n-2

Why are alkynes very reactive ?

They have a triple bond which is a region of high electron density

This electron rich triple bond allows alkynes to polarise other molecules and attract electrophiles

What type of reaction to alkynes tend to undergo ?

Addition reactions, where two or more molecules combine to form a single product

What type of reaction to alkenes tend to undergo ?

Addition reactions, where two or more molecules combine to form a single product

What is geometric isomerism ?

Occurs when two compounds have the same molecular formula but different spatial arrangements in their atoms

Why can’t alkanes form geo-isomers ?

Their single bonds have 360 degrees rotation

What is cis isomerism ?

two identical or similar atoms or groups are attached to the same side of a molecule

What is trans isomerism ?

two identical or similar atoms or groups are attached to opposite sides of a molecule

How do structural and geometric isomers differ from each other ?

Structural isomers differ in the way the atoms are connected to each other, but geometric isomers differ in the way those atoms are arranged in space

What are the physical properties of ethene ?

It is a colourless, flammable gas with a slightly sweet smell

Ethene burns with a luminous yellow, slightly smoky flame

It is non-polar, so it is soluble in cyclohexane but not in water