Module 4 Flashcards
whats a hydrocarbon
a compound containing carbon and hydrogen only
saturated hydrocarbon
has single bonds only
unsaturated hydrocarbon
contains double or triple bonds
homologous definition
a family of compounds with similar properties whose successive members differ by the addition of a CH2 group
whats a functional group
the part of the organic molecule that is largely responsible for the molecules chemical properties
aliphatic definition
carbon atoms are joined to each other in unbranched or branched chains or non aromatic rings
alicyclic definition
carbon atoms are joined to each other in ring structure with or without branches
aromatic definition
some or all of the carbon atoms are found in a benzene ring
alkynes
contain a triple bond
empirical formula
is the simplest whole number ratio of the atoms of each element present in a compound
general formula
the simplest algebraic formula for any member of a homologous series
molecular formula
shows the number and type of atoms of each element present in a molecule
structural isomerism
compounds with the same molecular formula but different structural formulae
homolytic fission
each of the bonded atoms takes one of the shared pair of electrons from the bond
radical definition
an atoms or group of atoms with an unpaired electrons
heterolytic fission
when a covalent bond breaks one of the atoms takes both the electrons from the bond
curly arrows
show the movement of a pair of electrons
the bonding in alkanes
only contain single bonds (saturated)
sigma bonds
shape of alkanes
tetrahedral arrangement around each carbon atoms with a bond angle of 109.5
boiling points in alkanes
as the chain length increases so does the boiling point as london forces act between molecules that are in close surface contact so as chain length increases the molecules have a larger surface area with more surfaace contact between molecules , so london forces will be greater
affects of branching on boiling point of alkanes
branched isomers have lower boiling points as there will be fewer surface contact between molecules of the branched alkanes giving fewer london forces
reactivity of alkanes
do not react with most common reagents because:
c-c and c-h sigma bonds are strong
c-c bonds are non-polar
c-h electronegativity is similar so baso non polar
alkanes + halogens mechanism name
free radical substitution
conditions for free radical sub
uv light
what happens in initiation
covalent bond in a halogen molecule is broken by homolytic fission and 2 radicals are formed
what happens in propogation
usually 2 steps where a halogen radical is reacting with an CH4 (as an example) to form CH3 and a hydrogen halide, this CH3 radical then reacts with eg br2 to from CH3Br and a br radical to react again with CH4
what happens in termination
2 radicals collide forming a molecule with all electrons paired
limitations of radical sub
further substitution
substitution at different positions in a carbon chain
structure of alkenes
unsaturated hydrocarbons
pi bond which locks the 2 carbon atoms in position and prevents rotation
whats a pi bond
the sideways overlap of 2 p orbitals above and below the carbon atoms
conditions for E/Z isomerism
c=c
different groups attached to each carbon atom of the double bond
Z isomerism
both priority groups are on the same side of the double bond
E isomerism
the priority groups are on different side of the double bond
priority groups in isomerism
the higher the atomic number the higher the priority
cis/trans isomer
one of the attached groups on each carbon atom of the double bond must be the same
cis isomer
baso same as z isomer , both groups on the same side
trans isomer
baso same as a E isomer , groups on opposite side of the double bond
reactivity of alkene
more reactive than alkanes because of the presence of the pi bond which as an electron dense area and so alkenes undergo addition reactions quite easily
hydrogenation of alkenes
h2 and a nickel catalyst at 423k
halogenation of alkenes
at rtp with a halogen
testing for unsaturation
add bromine water to solution , if theres a double bond the solution turns colourless
