alkenes

Covalent bond

Forms when two atoms share a pair of electrons and thr atomic orbitals from two atoms overlap

Sigma bonds

-the overlapping of two orbitals

-single bonds are always sigma bonds- easier to form as maximise overlap

-higher level of attraction between nuclei and shared electrons- strong bond

-free to rotate

Pi bonds

Half filled lorbitals can bend inwards and overlap sideways

-unable to rotate freely

-weaker than sigma bonds as the electrons are further away from the nucleus

Why are alkenes more reactive than alkanes

-the pi bond is weaker than the sigma bond and is broken first

-this also means that double bonds are stronger than single bonds but not double the strength

Elecrophile

A species which is attracted to a religion of high electron density

How does alkene form alkane

Reacts with hydrogen in the presents of nickel catalyst

Alkene to produce alcohol

React with stram in the presence of an acid (H3PO4) catalyst and heat

Alkene to form diol

Water and potassium managate (KMnO4)

Pale purple solution to colourless

Oxidises double bond

Heterolytic fission

The breaking of a covalent bond where one atom takes both shared electrons forming a negatively charged ion and a positively charged ion

Benefits of polymers

-readily available cheap alternative to metal glass paper and cardboard materials in everyday use

-low reactivity- useful for food packaging but non biodegradable

-manufactured large scale in diff shapes

-lightweight

recycling

-converting polymer waste into other materials

-reduces amount of waste going to landfill sites and reduce use of finite resources like crude oil

-time consuming- sorted and then processed

-some polymers can cause problems when recycled- e.g PVC contains a large amount pf toxic chlorine to be released- can be overcome by dissolving polymer and precipitating out the recycled material

Incineration

-some netroleum gas or natural gas derived polymers are still difficult to recycle

-an incinerator takes polymer waste and converts it to heat energy to heat homes and factories or to generate electricity

-the carbon in polymers can be released as carbon dioxide and other toxic waste is released like hydrogen chloride

Feedstock recycling

-waste polymers are broken down into gases, mainly hydrogen and carbon monoxide

-used as raw materials in the production of new polymers and other chemical reactions

-works with unsourced amd unwashed polymers

Sustainability

-use chemicals that are safe and environmentally friendly

-reduce number of chemicals

-use renewable feedstock chemicals

-reduce energy requirements

-improve atom economy

-consider lifespan of polymer

Life cycle analysis

-evaluate a products total env impact

-from raw material extraction to manufacturing to use and transport and disposal

Limiting problems of polymer disposal by removing toxic waste

-the waste gases from incinerator are reacted with a base or carbonate which reacts with acidic HCL gas, neutralising it

E.g CaO + 2HCl —> CaCl2 + H2o

Biodegradable Polymers

-can be broken down overtime using microorganisms, forms co2 water and organic compounds

-polyester and polyamide condensation polymers are biodegradable- hydrolysis

-made from plant material so land to grow the plants is needed

-breakdown in env so the hydrogen and carbon products cannot be directly used