Organic Groups Flashcards
What are saturated hydrocarbons?
Alkanes (formed from only hydrogen & carbon with just single bonds)
Are alkanes saturated or unsaturated hydrocarbons?
Alkanes are saturated hydrocarbons
What’s the general formula for alkanes with no ring?
Cn H2n+2
What type of bond do alkenes contain?
Double bond between carbon atoms
What type of bond do alkynes contain?
Triple bond between 2 carbon atoms
What are arenes?
Compounds that contain a benzene ring
What are aliphatic compounds?
Compounds that don’t contain a benzene ring
What are structural isomers?
Molecules with the same molecular formula (same number and type of atoms) but with different structures (atoms connected in a different order) they are different compounds with different properties
What’s the general formula for cycloalkanes
Cn H2n (unless there’s more than 1 ring)
What are small alkane molecules like? ( up to 4C)
Colourless gases
What are medium (5 to 16C) alkanes like?
Colourless liquids
What are large alkanes like?
White waxy solids
Why are alkane molecules non-polar?
C & H have very similar electronegativity values
Why are alkanes good fuels?
They don’t burn until ignited (have very high activation energies) & when they do burn a lot of energy is given out
What is an alkene?
hydrocarbons which contain one or more C=C, they are therefore unsaturated
what does a functional group determine?
how a molecule reacts
what’s the formula for alkenes with one double bond and no rings?
CnH2n
where do the shared pair of electrons of each covalent bond exist?
in a molecular orbital
what are the two main types of molecular orbital?
sigma and pi
how are atoms bonded together in molecules?
covalently
where is the shared pair of electrons in a sigma bond?
directly between the 2 nuclei
what’s the strongest type of covalent bond?
sigma bonds
why are sigma bonds the most common type of covalent bond?
all single bonds are sigma bonds and the first bond of a double or triple bond will also be a sigma bond
draw a double bond (as pi and sigma)
the weird burger thing
what reaction do alkenes undergo?
electrophilic addition reactions
why are C=C prone to attack by electrophiles?
it consists of 2 pairs of electrons so is very electron rich (high electron density & the pi bond sticks out above and below the plane of the molecule)
define electrophilic addition reaction
an addition reaction where 2 molecules react to give just 1 product molecule (by adding together)
what’s the difference between a pi bond and a sigma bond?
a sigma bond is caused by the direct overlap of the p-orbitals of carbon atoms, pi bond are caused by the indirect ‘leaning’ overlap of p-orbitals
which bond breaks when alkenes react?
the pi bond
under which conditions do alkenes react with Br2 (both pure liquid bromine and br water)?
at room temperature and pressure
how can you test for alkenes/unsaturated molecules?
add a few drops of bromine water (orange) and shake well, if the compound is unsaturated, a colour change from orange to colourless is seen
draw the mechanism for electrophilic addition
what is a carbocation?
a compound containing a carbon atom bearing a positive charge
what conditions do you need to react an alkene with hydrogen bromide?
room temperature and pressure
how many products will there be if a unsymmetrical alkene is reacted with hydrogen bromide?
2 (the bromine could be on either side of the carbon double bond)
what are the reagents for a reaction between an alkene and water?
an alkene and water(steam)
must include steam!
what are the conditions to react an alkene an water?
high temperature, high pressure and a phosphoric acid catalyst
what are the conditions needed to react an alkene with hydrogen?
platinum catalyst under room teperature and pressure
or
nickel catalyst with high temperature and pressure
what is a cycloalkane?
alkanes with a ring of carbon atoms, with two hydrogens attached to each carbon
why are benzene rings so stable?
the double bond electrons are delocalised around the carbon ring (they’re not attached to any particular carbon atom)
what’s the general formula for an alcohol?
CnH2n+1OH
Define an electrophile
A positive ion or molecule with a delta+ (slightly positive) region which is attracted to a negative region in a molecule, and reacts by accepting a pair of electrons to form a covalent bond
