Organic chemistry Flashcards
Carbon electron arrangement:
2,4
Because Carbon has four valence electrons….
carbon atom will covalently bond to 4 other carbon atoms.
Define the term hydrocarbon.
The simplest organic compounds that contain only hydrogen atoms and carbon atoms.
Structural formula:
shows how atoms are joined together
Condensed structural formula:
is used to represent organic compounds especially for larger molecules.
Molecular formula:
gives information about the type and number of atoms present in a substance.
Define the term homologous series
Is a family of organic compounds that can be represented by a general formula in which each successive member of the series differs by a -CH2- unit. Often have similar chemical properties.
Define the term functional group
Atoms or groups of atoms which influence the chemical behaviour of a compound.
Define the term ‘ saturated hydrocarbon’
Hydrocarbons that contain only single bonds between carbon atoms.
Alkane general formula:
CnH2n+2
Constitutional/structural isomers
have the same molecular formula but their atoms are connected differently.
Describe and explain the common physical properties of alkanes such as physical state, solubility, and trends in melting point and boiling point.
(1. Colour
2. solubility
3. Conductivity
4. melting/boiling points)
- Colourless compounds
Are non-polar and hence are insoluble in water - Have densities less than water so they float on water
- Do not conduct head or electricity because they do not contain ions or electrons which are free to move.
- Show increased melting and boiling points as the length of the carbon chain increases.
Know the substitution reactions of alkanes with halogens
- Loss of hydrogen atom - involves breaking a C-H bond
- Replacement of the lost hydrogen with a halogen atom
- The presence of a catalyst - usually UV light.
Alkene general formula:
CnH2n
Define the term geometrical isomers
when the atoms in the molecule have the same order of connectivity but different arrangement in space.
Cis isomers
the same groups are on the same side of the double bond.
Trans isomers
the same groups are on opposite sides of the double bond
Explain the reasons for existence of cis-trans isomers in alkenes
Geometric isomerism exists because free rotation around the carbon-carbon double bond cannot occur, fixing the position in space of the groups attached to the carbon atoms of the double bond.
Describe and explain the common physical properties of alkenes such as physical state, solubility, conductivity and trends in melting point and boiling point.
- Solubility
- melting point
- Density
- State
- insoluble in water
- Show increase in melting point as chain length (molar mass) increases
- Less dense than water
- At room temperature, ethene, propene, and butene are gases. Alkenes of higher molar mass are liquids.
addition reactions of alkenes with Halogenation (Cl2, Br2) reaction
is an addition reaction where a halogen molecule (two halogen atoms), usually chlorine or bromine, add across the double bond.
Know the addition reactions of alkenes with (H2)
is an addition reaction where a hydrogen atom (two hydrogen atoms) add across the double bond of an alkene to form an alkane molecule. A catalyst, usually nickel at 150°C or platinum at room temperature
Know the addition reactions of alkenes with Hydration (H2O)
Hydration is an addition reaction in which an alkene reacts with steam, water, to from an alcohol. In this reaction double bond is broken. One carbon of the double bond accepts a hydrogen, and the other accepts OH.
Know and explain Markovnikov’s rule for addition reactions.
In asymmetrical alkenes, the carbon of the double bond that has more hydrogen atoms receives the hydrogen forming the major product.
Major product -
formed in large quantities
Minor product -
formed in small quantities
Define the term unsaturated.
a molecule that contains double or triple carbon bonds.
Test for alkene/ alkane using Br2
Bromine is used to test for unsaturation, since bromine loses its brown colour when it reacts with alkenes. Alkenes react readily react without catalyst, whereas alkanes require sunlight and react slowly.
Test for alkene/ alkane using MnO4⁻
When the reaction is carried out in acidic conditions, purple-coloured permanganate decolourises to form Mn2+ ions when in prescence of alkene. In the acidic conditions, further oxidation of the diol occurs.
Substitution
An atom is replaced by another atom/group of atoms.
Addition
One bond of the carbon double bond breaks and an atom/ group of atoms adds to each of the adjacent carbon atoms. The organic product is saturated.
Polymer
large molecules made of many small repeating units known as monomers.
Monomer
atoms or small molecules that bond together to form more complex structures such as polymers.
Explain how addition polymers are formed from alkenes
Alkenes form addition polymers in a polymerisation reaction. Carbon-carbon double bond is broken, to form polymers.
Alkyne general formula:
CnH2n-2
What is the solubility of alkynes
Alkynes are insoluble in water.
What is the density of alkynes
Less dense than water
What is the boiling point of alkynes
Boiling point of alkynes increase with higher molar mass as the intermolecular forces increase. Hence more energy is needed to overcome these forces of attraction.
Primary haloalkane
The carbon atom to which the halogen is attached is further attached to one carbon atom.
Secondary haloalkane
The carbon atom to which the halogen is attached to is further attached to two other carbon atoms.
Tertiary haloalkane
The carbon atom to which the halogen is attached is further attached to three other carbon atoms.
Describe and explain the common physical properties of haloalkanes such as physical state, solubility and trends in melting point and boiling point.
- Colour/odour
- Solubility
- Boiling point in relation to alkanes
- Boiling point in relation to size
- Colourless odourless compounds.
- Hydrophobic in nature.
- Haloalkanes have higher boiling point than alkanes, if the number of carbon atoms is the same.
- The boiling point of haloalkanes increases with the increasing number of halogens in haloalkanes.
Know the reaction of haloalkanes with ammonia.
Haloalkanes undergo substitution reaction with ammonia. The halogen is removed and replaced by NH2 to form amines.