Alkanes Flashcards
General formula for alkanes
CnH2n+2
characteristicsof alkanes
- group of saturated hydrocarbons
- all alkanes are sp3 hybridized
- boiling point and melting poin increases as the number of C atoms become larger
- isomers with most branched chains have the lowest boiling point
- alkanes are less dense than water
- alkanes are insoluble in waer
why does branching lower boiling point
branching lowers the surface area of molecules making them more spherical and preventing close contact among the molecules
hence the strength of intermolecular forces decrease
why does boiling and melting point increase with increasing carbon atoms
as the molecules become bigger and the number of carbon atoms increases there will be much more contact points over which attractions can occur
many weak attractions will make a strong force
undecane vs dodecane isomer
un- C11H24
do- C12H26
reactivity of alkanes
they are very unreactive due to being non-polar since the C and H have similar electronegativity, and lack of mulyiple bonds
3 types of alkane reactions
- free radical substitution
- combustion
- cracking
what is cracking
reaction which converts large alkane molecules into smaller alkanes and alkenes
reason for cracking
smaller alkanes make better fuels since it is easier to burn
alkenes are used as monomers to form addition polymers
methods of cracking
- thermolytic cracking
- catalytic cracking
how is thermolytic cracking done
done by heating alkane up to 800 deg Celsius
how is catalytic cracking done
done by heating he alkane up to 650 deg Celsius in the presence of an Al2O3 catalyst
what is combustion of alkanes
when an alkane is burnt, CO2 and H2O are produced, as well as, energy
general reaction equation for combustion
1 CxHy + (x + y/4) O2 —> y/2 H2O + x CO2 + energy
what is free radical substitution
photochemical reactions that take place only in the presence of sunlight or ultraviolet light
