organic chemistry Flashcards
define homologous series
series of organic compounds having the same functional group
define structural isomer
same molecular formula but different structural formula
define functional group
part of an organic molecule that is largely responsible for the molecules chemical properties
alcohol functional group/prefix/suffix
-OH/hydroxy-/-ol
haloalkane functional group/prefix
-Cl,Br,I/chloro,bromo,iodo
aldehyde functional group/suffix
-CHO/al
ketone functional group/suffix
-C(CO)C-/one
carboxylic acid functional group/suffix
-COOH/oic acid
ester functional group/suffix
-COOC-/oate
acyl chloride functional group/suffix
-COCl/oyl chloride
amine functional group/prefix/suffix
-NH2/amino/amine
nitrile functional group/suffix
-CN/nitrile
How is a sigma bond formed
Carbon has 4 electrons in its outer shell. S orbital is filled. 2 of the p orbitals are half-filled and one is completely empty so they overlap
How is a pi bond formed
There is 1 electron in each carbon not involved, this electron is in the p orbital. The pi bond is formed by the sideways overlap of the p orbitals. Each carbon contributes one electron to the electron pair. Weaker bond
can pi bonds rotate
no because of the double carbon to carbon bond, would otherwise break.
How do you get E/Z isomerism
2 different groups attached to the carbons. A double carbon bond. Occurs due to restricted rotation
z / cis isomers
non H groups on the same side of the double bond
E/trans isomers
non H groups on different sides of the double bond
define stereoisomers
same structural formula but a different arrangement of the atoms in space
what is optical isomerism
can occur in a wide range of compounds including alkanes with no functional group
order the elements with increasing priority
H, C, N, O, Cl, Br
pattern with boiling points as the length of the chain increases
Longer the chain, the higher the boiling point because there is more surface contact so there are stronger London forces so more energy is needed to overcome these forces.
pattern with boiling points as the branching of the chain increases
The more branching, the lower the boiling point because there are fewer points of contact and the molecules are not as close together so there are weaker London forces meaning less energy is needed to overcome the forces.
why are alkanes unreactive
the sigma bonds are strong, C-C is non polar, and there is a small difference in electronegativity between C and H
why is carbon monoxide deadly
combines with haemoglobin to form carboxyhaemoglobin which prevent haemoglobin from transporting oxygen.
what are addition reactions
2 reactants join together to make one product
what are substitution reactions
an atom or group of atoms are replaced by a different atom or group of atoms
what are elimination reactions
removal of a small molecule from a large one
what is heterolytic fission
where 1 atom takes both electrons from the covalent bond
what is homolytic fission
where each atom take one electron from the covalent bond
what conditions are needed for free radical substitution
UV light
what are the different stages of free radical substitution
initiation, propagation and termination
what is made in initiation give an example
molecule — radical+radical
e.g. Cl2 – Cl. + Cl.
what is made in propagation give an example
radical + molecule —- radical + molecule
Cl. + CH4 —- Ch3. + HCl
CH3. + Cl2 —- CH3Cl + Cl.
what is made in termination give an example
radical + radical —– molecule
CH3. + CH3. —- C2H6
CH3. + Cl. —- CH3Cl
Cl. + Cl. —– Cl2
Why are alkenes more reactive
pi bond has a lower enthalpy than a sigma bond so it is broken more easily
reactants/conditions for hydrogenation
hydrogen/nickel + heat
reactants/conditions for halogenation
any halogen/room temperature - used as a test for saturation
reactants/conditions for hydrogenated halides
gaseous or concentrated solution of a hydrogenated halide - can form 2 products
reactants/conditions for hydration
steam/phosphoric acid - can form 2 products
Describe electrophilic addition
the double bond in an alkene represents a region of high electron density because of the presence of a pi electron. The high density attracts electrophiles which accepts an electron pair
What is a nucleophile
electron pair donors
what is an electrophile
electron pair acceptors
what is markownikoff’s rule
addition of a hydrogen halide etc to an unsymmetrical alkene forms the major product through the most stable carbocation
order of carbocation stability starting with least stable
primary (2 H), secondary (1 H), tertiary (0 H)
Primary alcohol
carbon with OH is attached to one alkyl group
Secondary alcohol
carbon with OH is attached to two alkyl group
Tertiary alcohol
carbon with OH is attached to three alkyl group
during oxidation what does a primary alcohol produce
aldehyde then carboxylic acid
during oxidation what does a secondary alcohol produce
ketone
during oxidation what does a tertiary alcohol produce
no reaction
what is used to oxidize alcohols
potassium dichromate (K2Cr2O7) and sulfuric acid (H2SO4)
what color change is observed during oxidation
orange to green
How can you make sure an aldehyde is produced from oxidation of a primary alcohol
distillation - aldehydes have a lower boiling points than alcohols, the aldehyde evaporates before it can react with anymore oxidizing agent
Describe heating under reflux
allows you to boil a liquid. The vapor condenses in a vertical condenser and returns to the reaction vessel so no substance is lost.
dehydration of alcohols
H3PO4 or H2SO4 as a catalyst. Water is also produced. Heated under reflux
substitution of alcohols. Give example equation
heated under reflux with H2SO4 and sodium halide. e.g. C3H7OH + NaBr + H2SO4 —- C3H7Br + NaHSO4 +H2O.
examples of nucleophiles
:OH-, H2O: and :NH3
describe nucleophilic substitution hydrolysis
nucleophile approaches carbon atoms attached to halogen on the opposite side of the molecule from the halogen atom. Direction minimizes repulsion between nucleophile and negative halogen. Lone pair of electrons on OH- is attracted and donated to positive carbon. Carbon - halogen bond breaks via heterolytic fission. Alcohol plus halide ion formed. Heated under reflux and aqueous sodium hydroxide is used.
cl. reacting with ozone
- Cl. + O3 —– ClO. + O2
- ClO. + O —- Cl. + O2
- O3 + O —- 2O2
what is the ozone molecule
O3
breakdown of ozone NO.
- NO. + O3 —- NO2+O2
- NO2. + O —– NO. + O2
- O3+ O —- 2O2
when is NO. formed
During lightening strikes and a result of aircraft travel in the stratosphere
CFC properties
stable due to string carbon to halogen bond. UV light provides sufficient energy to break carbon halogen bond. As C-Cl bond is lowest enthalpy a CL. is formed
properties of aerosols
non-toxic, Low BP, low reactivity
ozone formation formula
O2 + O —- O3
consequences of ozone breakdown
skin cancer, cataracts, low crop yield, famine as high food prices, more sunburn
what is a sigma bond
overlap of orbitals between atoms
what is optical isomerism
same structural formula but are non-superimposable mirror images of each other
Describe how to purify an organic product
- Ensure that the tap of the separating funnel is closed.
- Pour the mixture of liquids into the separating funnel, place a stopper in the top of the funnel, and invert to mix the contents.
- Allow the layers to settle.
- Add some water to see which layer increases in volume - this is the aqueous layer.
- Place a conical flask under the separating funnel, remove the stopper and open the tap until the whole of the lower level has left the funnel.
- Place a second conical flask under the separating funnel to collect the other layer.
- You will now have one conical flask containing the aqueous layer and the other containing the organic layer.
How can you remove acid impurities when purifying an organic product
Add aqueous sodium carbonate to the separating funnel and invert the mixture. Carbon dioxide is produced and the tap needs to be slowly opened, holding the stoppered separating funnel upside down, to release any gas pressure that may have been built up. Aqueous sodium carbonate layer is removed and organic layer is washed with water before running both layers off into separate conical flasks.
How do you dry an organic product
- Add organic liquid to a conical flask
- using a spatula, add some of the drying agent (e.g.CaSO4) to the liquid and gently swirl the contents to mix together.
- Place a stopper on the flask to prevent the mixture from evaporating away. Leave for about 10 minutes.
- If the solid has all stuck together in a lump, there is still some water present. Add more drying agent until some solid it’s dispersed in the solution as a fine powder.
- Decant the liquid from the solid into another flask. If the liquid is dry it should be clear.
Why is a tertiary carbocation more stable than a primary carbocation
Because there are more alkyl groups around the carbon. Alkyl groups electron releasing/positive inductive effect.
Reflux:
The continual boiling and condensing of a reaction mixture back into the original container to ensure that the reaction takes place without the contents of the flask boiling dry.
