Alkanes Flashcards
what are alkanes?
-naturally occurring hydrocarbons formed from crude oil
what are alkanes formed by?
The conversion of animal and vegetable matter, which existed under pressure for millions of years
why are alkanes saturated compounds?
since they contain single c-c and c-h covalent bonds only
what is the shape of an Alkane?
-Each carbon bond makes four bonds
-Around each atom, there are 4 bonding pairs of electrons which repel.
-Thus each carbon atom is at the centre of a tetrahedral structure, with either carbon or hydrogen atoms at the apices of the tetrahedron
What are the bond angles of alkanes?
109°
What are all bonds between carbon atoms or between a carbon and hydrogen atom?
-Sigma bonds
what are all sigma bonds able to do?
freely rotate
what are sigma bonds formed by?
Sigma bonds are formed by the direct overlap of orbitals directly between the bonding atoms
what does alkanes being saturated hydrocarbons mean?
They have no double or triple bonds
What are the three distinctive types of alkanes?
-straight chained alkanes
-branched chained alkanes
-ring or cycloalkanes
What is an example of a straight chained alkane?
Butane
What is an example of a branched chained alkane?
2-methylpropane
What is an example of a ring or cyclo alkane?
cyclobutane
What type of forces are between the many (successive) molecules of an alkanes?
Induced dipole dipole interactions
What happens to boiling point as the length of the carbon chain increases?
-Boiling point increases
-Larger molecules have greater surface contact and therefore greater induced dipole-dipole interactions
-more energy is required to overcome the greater induced dipole-dipole forces and separate the molecules so the boiling point is higher