structure of alkenes Flashcards
what is the general formula of carbon and hydrogen?
general formula is CnH2n - for non-cyclic alkenes
what is hybridisation ?
It is the combination of S and P orbitals overlapping whilst giving a rise to a new orbital
what is the trend of alkanes boiling points and melting point ? (physical )
The more carbon atoms there are the greater the intermolecular forces where lots of energy is required to separate the molecules
The melting point increases as the carbon chains get longer so there will be more electrons in the molecule - greater intermolecular forces is need to break the molecules
why is alkanes soluble in water ?
Alkanes are non polar so they are immiscible in water
they are soluble in most organic solvents
why are alkanes fairly reactive ?
They are fairly reactive and they have strong non polar single covalent bonds
why are alkanes fairly reactive ?
They are fairly reactive and they have strong non polar single covalent bonds
what is the complete and incomplete combustion equation of alkane
complete - CH4(g) + 2O2(g) ——> CO2(g) + 2H2O(l)
incomplete - CH4(g) + 1½O2(g) ——> CO(g) + 2H2O(l)
The greater number of carbon atoms, the more energy produced and the greater the amount of oxygen needed for complete combustion.
what is the definition of heterolytic fission ?
When a covalent bond is broken the shared paired of electrons is taken by the atoms
what are the properties of breaking covalent bonds ?
If several bonds are present the weakest bond is usually broken first
Energy to break bonds can come from of energy sources such as heat / light
Reaction between methane and chlorine
what are the general properties of free radicals ?
reactive species such as atoms or groups possess an unpaired electron
their reactivity is due to to pairing up the single electron
formed by homolytic fission (homolysis) of covalent bonds
formed during the reaction between chlorine and methane
formed during thermal cracking and reactions taking place in ozone layer
what is the chlorination of methane
Reagants - chlorine and methane
Conditions UV light or sunlight and heat
Mixtures- free radicals are very reactive as they are trying to pair their electron with sufficient chlorine, every hydrogen will eventually be replaced.
Mechanism - Mechanisms shows what chemists think is going on in the reaction, whereas an equation tells you the ratio of products and reactants.
Chain reaction - Chlorination of methane proceeds free radical substituation because methane is attacked by free radicals resulting in hydrogen atoms being substituted by chlorine atoms.
what happens during the process of initiation ?
During initiation, the weakest bond is broken first (halogen) as it requires less energy.
