Chapter 11 - Organic Chemistry 1 Hydrocarbons Flashcards
What is organic chemistry?
- It is simply the chemistry of the millions of known compounds if carbon.
- There a few expectations such as the carbonates, and the oxides of carbon that are generally classified as inorganic.
When do hydrocarbons undergo combustion or oxidation?
When ignited in the presence of air or oxygen.
What are the general features of the straight chain and branched chain Alkanes include?
- They consist only of carbon and hydrogen.
- They have only single bonds between the carbon atoms, eg. Propane CH3-CH2-CH3
- They have the general formula CnH2n+2.
- They are colour less and may be gases, liquids or solids at room temperature depending on their relative formula mass.
- They are insoluble in water.
What does IUPAC stand for?
International Union of Pure and Applied Chemistry
What are Structural Isomers?
Structural isomers are compounds that have the same molecular formula but different structural formulas.
What is a Substitution reaction?
It is one in which an atom in a molecule is replaced by a different atom to form a new molecule.
What has to happen for substitution reactions to occur?
- The reaction mixture must be exposed to ultraviolet light (or sunlight).
- These reactions occur very slowly.
What kind of reactions do cycloalkanes go through?
- Combustion
* Substitution
What are the general properties for Alkenes?
- They contain only carbon and hydrogen atoms.
- They have at least one double carbon-carbon bond.
- They have a general formula of CnH2n.
- They are colour less compounds.
- They have relatively low melting and boiling points.
- They are insoluble.
Why do Geometrical isomerism occur for Alkenes?
- Because the carbon atoms joined by the double bond are unable to rotate about the double bond.
- An alkene will exhibit geometrical isomerism if each of the carbon atoms joined by the double bond have different groups attached to them.
What kind of reactions do Alkenes undergo?
Addition reactions readily with substances such as chlorine, bromine, fluorine, hydrogen halides and water (steam).
What happens in an Addition reaction?
- Two new atoms are added ‘across the double bond’ and the double bond becomes a single bond.
- Addition reactions normally occur at a much faster rate than substitution reactions.
How can an Alkane and an Alkene be distinguished in an experiment?
- By adding an aqueous solution of bromine.
- An aqueous solution of bromine is an orange colour and when it reacts with either an Alkane or an Alkene, a colorless mixture is formed.
- When an Alkene is shaken with an aqueous solution of bromine, the orange colour of bromine disappears almost instantly.
- However, with Alkanes, the orange colour of bromine takes a much longer time to disappear and ultraviolet light is necessary for reaction to occur.
Can Alkenes undergo addition reactions followed by substitution reactions with halogens?
Yes if ultraviolet light is present and it the reaction mixture is allowed to react for sufficient time.
What are the required conditions for a substitution reaction to occur after an addition reaction?
- The halogen and Alkene need to be I initially present in greater than a 1:1 mole ratio mixture.
- If an Alkene is mixed with excess halogen and allowed to react in the dark, then only an addition reaction will occur.
