2.4- Organic Compounds Flashcards
(b)
Nomenclature rules relating to alkanes, alkenes, halgenoalkenes, alcohols and carboxylic acids.
Alkanes:
CnH2n+2
Alkenes:
CnH2n
Halogenoalkanes:
CnH2n+1X
Prefix: Fluoro-/Chloro-/Bromo-/Iodo-
Suffix: -ane
Alcohols:
CnH2n+2OH
Carboxylic acids:
CnH2n+1COOH
(c)
Effect of increasing chain length on
melting/boiling temperature and solubility
Increasing Chain Length
-Increases melting/boiling temperature (stronger van der Waals forces)
-Decreases solubility in polar solvents (water)
(c)
Effect of the presence of functional groups on melting/boiling temperature and solubility
Presence of Functional Groups
- Increases melting/boiling temperature if polar (due to hydrogen bonding/dipole-dipole interactions)
- Increases solubility in polar solvents if polar functional group present (due to hydrogen bonding)
(d)
Structural isomerism
Structural isomers are compounds with the same molecular formula but a different structural formula
(d)
Chain isomerism
The carbon chain is arranged differently (branches).
(d)
Position isomerism
The functional group is in a different position in the molecule.
E.g.
CH3 CH2 CH2
Cl
1-chloropropane
CH3 CH CH2
Cl
2-chloropropane
(d)
Functional group isomerism
The functional group is different
(d)
E-Z isomerism
Only occurs in alkenes because there is restricted rotation around the double bond.
(d)
Working out if the alkene is E or Z
Look at the atoms directly attached to each of the carbon atoms. The atom with the higher atomic number takes priority. If the higher priority atom on both carbon atoms is on the same side of the double bond, the isomer is the Z form. If the higher priority atoms are on opposite sides of the double bond, the isomer is the E form.
Identfiying functional groups as primary/secondary/tertiary
Primary: Functional group attached to a carbon bonded to one other carbon.
Secondary: Functional group attached to a carbon bonded to two other carbons.
Tertiary: Functional group attached to a carbon bonded to three other carbons.
Electronegativity
Electronegativity is a chemical property that describes the tendency of an atom or a functional group to attract electrons toward itself
Non-polar covalent bond
Bonding electrons shared equally between two atoms. No charges on atoms. E.g. C-H, Cl-Cl
Polar covalent bond
Bonding electrons shared unequally between two atoms. Partial charges on atoms. E.g. C-X (C= delta positive and X= delta negative)
(x = Cl, Br, I, O)
Hydrogen bonds
Occur between a Hydrogen bonded to a N, O, F and an N, O or F atom
on another molecule
Dipole-Dipole
Dipole-dipole forces are attractive forces between the positive dipole
of one polar molecule and the negative dipole of another polar
molecule
Induced Dipole- Induced Dipole
These are weak electrostatic forces that attract molecules to one
another – even non-polar molecules
The more strength increases the more total electrons there are in a
molecule. So the interactions are stronger when there is a higher
surface area (i.e. longer chain length)
Alkene bonds
Alkenes contain C=C bonds
These are made up of a sigma bond and a pi bond (whereas alkanes only contain sigma bonds)
Formation of sigma bonds
Sigma bonds are formed from the overlap of s orbitals on each carbon
Formation of pi bonds
Pi bonds are formed from the overlap of p orbitals on
each carbon
Electrophilic addition
Alkenes undergo electrophilic addition reactions when they react with an electrophile
Impact of intermolecular forces on boiling points of organic compounds
Melting and boiling points depend on the strength of intermolecular
forces – this is because in order for a compound to melt/boil the
intermolecular forces have to be broken
(2)
Impact of intermolecular forces on boiling points of organic compounds
The stronger the interactions – the higher the melting/boiling point
This is because more energy is needed to break the molecules
apart
Impact of intermolecular forces on solubility of organic compounds
When a compound dissolves the intermolecular forces between molecules break and new forces between the solute and the solvent are formed. Energy is needed to do this - all compounds are more soluble at higher temperatures
(2)
Impact of intermolecular forces on solubility of organic compounds
Non-polar compounds dissolve in non-polar solvent
Polar compound dissolve in polar solvent
Combustion of hydrocarbons
Burning a hydrocarbon forms two compounds:
CO2 and H2O
Complete combustion
Requires excess O2
Produces only CO2 & H2O
Incomplete combustion
Occurs when there is an insufficient supply of oxygen
Produces water and CO(g) and/or C(s)
(e)
Electrophiles
An electrophile is a species that accepts a lone pair of electrons in a reaction.
(e)
Nucleophiles
A nucleophile is a species that donates a lone pair of electrons in a reaction.
(e)
Radicals
A free radical is a neutral
molecule that has an
unpaired electron.
(e)
Heterolytic bond fission
Heterolytic bond fission is the breaking of a covalent bond where one of the bonded atoms gets both electrons. This produces one nucleophile and one electrophile.
(e)
Homolytic bond fission
Homolytic bond fission is the breaking of a covalent bond where both bonded atoms get one electron, producing free radicals.
