Alkenes
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What is the general formula for alkanes
Cn H2n
What type of hydrocarbons are alkenes
Unsaturated hydrocarbons because they captain at least one double covalent bond between the carbon atoms
Alkenes will generally have less what?
Hydrogens
Why are C=C bonds unsaturated
Because they make more bonds with extra atoms in addition reactions
How many pairs of electrons are found in C=C and what does this result to?
• Two pairs of electrons • High electron density • Makes alkenes reactive
What type of alkene would have 2 Hs less than the equivalent open-chain alkene
Cyclic alkenes
What type of addition reaction happens with alkenes?
Electrophilic addition reactions
How do electrophilic addition reactions happen?
The double bonds open up and atoms are added to the carbon atoms
Why do electrophilic addition reactions happen?
The double bond has got plenty of electrons and is easily attacked by electrophiles
What are electrophiles
Electron pair acceptors
What charge do electrophiles carry and why?
Positive charge because they are short of electrons
What is used to test for in saturation
Bromine water
Describe the test for unsaturation
• Shake an alkene with orange bromine water • The solution quickly decolourises • Colourless dibromoalkane • Via electrophilic addition
Name two compounds Alkenes undergo Electrophilic addition with
• Hydrogen halides • Sulphuric acid
What is formed when alkenes react with hydrogen bromide?
Halogenoalkanes
Adding hydrogen halides to unsymmetrical alkenes form what two products
A stable (major product) and an unstable Carbocation (minor product)
What is the difference between a stable product and an unstable product
A stable product will have more alkyl groups so it will be produced more
What are the three type of carbocations?
Primary, secondary and tertiary
Draw the mechanism for the reaction of propene with hydrogen bromide
Check physical flashcards for answers
What conditions are required to react alkenes with sulphuric acid and what product is formed?
• Cold concentrated sulphuric acid • Alkyl hydrogen sulphates
How are alkyl hydrogen sulfates formed into alcohols?
• Add cold water and warm the product • It hydrolyses to form an alcohol • The sulfuric acid is not used up, so it acts as a catalyst
Draw the mechanism for the reaction of ethene with sulfuric and cold water to form an alkyl hydrogen sulfate and an alcohol
Check physical flashcards for answers
What is carbocation
An organic ion containing a positively charge carbon atom
What is the iupac name of the major product of the reaction between 2-ethylbut-1-new and hydrogen bromide
3-bromo-3-methylpentane