Chapter 13
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Are alkenes saturated or unsaturated hydrocarbonds?
unsturated
What is the general formula of alkenes?
CₙH₂ₙ
What is a π-bond?
sideways overlap of 2 p-orbitals
What are stereoisomers?
same structural formula but different arrangement of atoms in space
Where does E/Z isomerism occur?
compounds with a C=C bond
What is cis-trans isomerism?
1) C=C bond 2) each carbon in double bond must be attached to 2 different groups - 1 must be hydrogen
Why are alkenes more reactive than alkanes?
because of the presence of the π-bond
What is hydrogenation of alkenes?
when an alkene is mixed with hydrogen + passed over nickel catalyst at 423K
What type of reaction is hydrogenation of alkenes?
addition
What is halogenation of alkenes?
when an alkene is mixed with chlorine/bromine at room temperature
What type of reaction is halogenation of alkenes?
addition
How do you test for unsaturation?
1) add bromine water (orange) drop-wise to alkene 2) bromine adds across double bond 3) orange colour disappears
What type of reaction is the reaction of alkenes with hydrogen halides?
addition
What is the reaction of alkenes with hydrogen halides?
when alkenes react with gaseous hydrogen halides at room temperature to form haloalkanes
What is the hydration of alkenes?
when alkenes react with steam in the presence of a phosphoric acid catalyst to form an alcohol
What type of reaction is the hydration of alkenes?
addition
What is an electrophile?
an atom/group of atoms that is attracted to an electron-rich centre + accepts an electron pair
What is a carbocation?
contains a positively charged carbon atom
What is the stability of carbocations linked to?
electron-donating ability of alkyl groups - the more alkyl groups attached to positively-charged carbon atom, the more the charge is spread out, making the ion more stable
What are polymers?
large molecules formed from thousands of repeat units of smaller units called monomers
What type of polymerisation do unsaturated alkene molecules undergo?
addition
Why is the disposal and recycling of PVC hazardous?
1) high chlorine content 2) range of additives present
What is feedstock recycling?
the chemical + thermal processes that reclaim monomers/gases/oil from waste polymers