4.1.2 alkanes Flashcards
what bond do alkanes have and define it
sigma bond-when 2 s-orbitals directly overlap
draw a diagram of the direct overlap between the 2-s orbitals
in booklet
what does how well the S-orbitals overlap determine
how well they overlap determines how strong the bond is
what is the shape around each carbon atom in alkanes
109.5 and tetrahedral
each carbon atom has 4 bonding pairs of electrons which repel each other equally
what happens as chain length increases
-larger surface area
-more surface contact
-more London forces
-requires more energy to overcome
why do alkanes have low reactivity
-the sigma bonds in the C-H and C-C have a large bond enthalpy
-they are non-polar so wont attract any positively or negatively charged particles
why is CO toxic
as it binds to haemoglobin instead of oxygen so less o2 will reach your cells
what is homolytic fission
when a covalent bond breaks by homolytic fission each atom from the bond takes one of the shared pairs of electrons
what are radicals
atoms or a group of atoms with an unpaired electron
how do induce a dipole in an atom
1-electrons are constantly on the move which leads to an uneven spread in electron density
2-this creates a temporary dipole
3-this temporary dipole will repel electrons in a nearby atom inducing a dipole in them
what else increases the melting point of the molecule apart from surface contact
more electrons
write the initiation, propagation and termination steps for
CH4 + Cl2–>CH3Cl + HCl
initiation-cl-cl -> cl +(R) + cl (R)
propagation-CH4 + cl(R) -> CH3(R) +HCl
CH3(R) + Cl2 -> CH3Cl + Cl(R)
write the initiation, propagation and termination steps for
C6H12 + Cl2–> C6H11Cl + HCL
initiation-cl-cl -> cl(R) +cl(R)
propagation-C6H12 + Cl(R) -> C6H11(R) + HCl
C6H11(R) + Cl2 -> C6H11Cl + Cl(R)
what are some limitations of radical substitution
-different radicals may collide to form unexpected products
-substitution at different points along the chain
what is the bond fission in the initation step
homolytic
