chapter 14- alkenes Flashcards
(26 cards)
what is the general formula of an alkene
Cn H2n
what is the shape angle of ethene
121 degrees
why is their restricted rotation with a carbon-carbon double bond
because the p-orbitals on each carbon overlap to form an orbital with a cloud of electron density above and below a single bond called a π orbital
what are the different types of isomers alkenes can form
positional isomers
geometrical isomers
what are position isomers
isomers with the double bond in different positions
what are geometric isomers
isomers with the same structural formula but bonds are arranged differently in space
what intermolecular forces do alkenes have
Van Der Waals forces
are alkenes or alkanes more reactive and why
alkenes are more reactive as they have a lower bond enthalpy
what does the combustion of alkenes produce
carbon dioxide and water
what is the positive inductive effect
the tendency of some atoms o groups of atoms to release electrons via a covalent bond to stabilize the positive charge of the intermediate carbocation
what is the most stable carbocation
the carbocation with the most alkyl groups
what does the reaction of alkenes and halogenoalkanes produce
dihalogenoalkanes
what is the test for a carbon-carbon double bond
bromine water test
orange/brown to colourless if present
what does an alkene (ethene) with concentrated sulfuric acid make
ethyl hydrogensulfate
what happens when you add water to the product of an alkene and concentrated sulfuric acid
alcohol is formed, and sulfuric acid is reformed
how does the reaction of an alkene and water take place
carried out with steam, at a suitable temperature and pressure, using an acid catalyst such as phosphoric acid
what is the symbol equation for the reaction of an alkene with water
CH2=CH2(g) + H2O(g) →CH3 CH2 OH(g)
what are polymers
large molecules built up of small molecules called monomers
what are addition polymers
they are built up from a monomer or monomers with a carbon-carbon double done
what are plasticisers
small molecules that get between the polymer chains forcing them apart and allowing them to slide across eachother, which modifies the property of the polymer
are polymers biodegradable
no, due to the long chain saturated alkane backbone which has strong and non-polar C-C and C-H bonds which are unreactive
what is high density poly(ethene) and how is it made
- made at temps and pressure just above room conditions
- uses a Ziegler-Natta catalyst
- results in a polymer with much less chain branching
- chains pack together well increasing the density of the plastic
- increasing the melting point
what is high density poly(ethene) and how is it made
- made by polymerising ethene at high temps and pressure
- done by a free radical mechanism
- produces a polymer with a certain amount of chain branching
- chains do not pack together relatively well decreasing the density of the plastic
- the product is flexible and stretches well
steps in mechanical recycling
- separate the different types of plastics
- plastics are washed then ground up into small pellets
- these are melted and remolded
