Chapter 6 - Organic chemistry I (L) Flashcards
What are hydrocarbons?
Compounds that contain only carbon and hydrogen
What are saturated hydrocarbons?
Hydrocarbons with the maximum amount of hydrogens possible
What are unsaturated hydrocarbons?
Hydrocarbons without the maximum amount of hydrogens possible
What does any compound ending in -ate contain?
Oxygen
What does a double bond always mean in terms of saturation?
The compound is unsaturated
What does all single bonds in a compound mean in terms of saturation?
The compound is saturated
What is a multiple bond?
Two or more covalent bonds between two atoms
What are displayed formulae?
They show every bond and atom separately
What are structural formulae?
Don’t show individual atoms, and can show bonds but can not. For example:
CH3CH2CH3 and CH3-CH2-CH3 are both structural formula of propane
What are skeletal formulae?
Each dot represents a carbon atom, and the line between represents the bond between them
What is the molecular formula?
Shows the actual number of atoms in a molecule
What is the empirical formula?
Shows the numbers of each atom in the simplest whole number ratio
What is a functional group?
An atom or group of atoms in a molecule that is responsible for its chemical reactions
What is a homologous series?
A group of compounds with the same functional group and general formula, which differ by CH2 from the next member
What is the general formula of alkanes?
Cn H2n+2
What is the general formula of alkenes?
Cn H2n
What is the general formula of halogenealkanes?
Cn H2+1 X (X = any halogen)
What is the general formula of alcohols?
Cn H2n+1 OH
What is the equation for the complete combustion of methane?
CH4 + 2O2 -> CO2 + 2H2O
What is nomenclature?
The rules of naming molecules
How do I revise nomenclature?
Read through the rules and then do practice questions
What are structural isomers?
Compounds with the same molecular formula but different structural formula
What are the two types of structural isomerism?
Chain and position isomerism
What is chain isomerism?
When molecules have different carbon chains e.g. Butane and Methyl-propane
What is position isomerism?
When molecules have the same functional group attached in different places e.g. Propan-1-ol and Propan-2-ol
Can both position and chain isomerism be present simultaneously?
Yes
What is stereoisomerism?
When molecules have the same molecular and structural formula, however a different spatial arrangement
What type of isomerism does geometric isomerism come under?
Stereoisomerism
What is geometric isomerism also known as?
Cis-trans isomerism
Where can geometric isomers occur and not occur?
It can occur in alkenes, but not in alkanes
Why can geometric isomers occur in alkenes but not alkanes?
Because the presence of C=C leads to restricted rotation, whereas in alkanes the atoms can rotate freely, without restriction
What is cis isomerism?
When the two alkyl groups are on the same side of the C=C
What is trans isomerism?
When the two alkyl groups are on opposite sides of the C=C
When does cis-trans notation not work and why is this the case?
When there are 4 different groups, because the idea of two identical groups being in a cis- or trans- arrangement does not work, as there are not two groups that are the same
In E-Z notation how do you decide which two atoms are the highest priority?
The atom with the highest atomic number on the left of the double bond, and the atom with the highest atomic number on the right of the double bond are the two atoms with the highest priority
What are geometric isomers?
Compounds containing a C=C, with the same molecular and structural formula, but with the atoms attached at different positions
What is a locant?
A number used to indicate which carbon atom in the chain an atom or group is attached to- e.g. in 2-methyl-propane, the methyl group would be attached to the second carbon (2 is the locant)
In E-Z notation, once you have found the two atoms with the highest priority, what do you do?
See whether the two atoms with the highest priority are opposite each other or not- if they are you have an E-isomer, if not you have a Z-isomer
Z meaning (German)
Zusammen = Together
E meaning (German)
Entgegen = Opposite
What are most compounds in crude oil and natural gas?
Alkanes
What are the 3 main processes used to convert crude oil into fuels?
- Cracking
- Reforming
- Fractional distillation
What is fractional distillation?
The process used to separate a liquid into fractions by boiling and condensing
As you go down in fractional distillation, what 4 trends will you see?
As you go down, it will be - hotter and the molecules will be - longer chains - less flammable - more viscous
In fractional distillation, where will you find the compounds with the highest boiling points?
At the bottom
What happens to the dissolved gases in crude oil during fractional distillation?
They rise to the top of the column without condensing
What is cracking?
The breakdown of longer chain molecules into smaller ones by heating with a catalyst
Why is the cracking of hydrocarbons important?
Because the demand for longer chain hydrocarbons is much less than the demand for shorter chain hydrocarbons, therefore cracking is used to turn longer chain into shorter chain hydrocarbons
What is the process of cracking hydrocarbons?
Longer chain hydrocarbons are passed through a heated catalyst, normally zeolite. This causes larger molecules to break up into at least 2 smaller molecules
What is the catalyst usually used in the cracking of hydrocarbons?
Zeolite, which is made up of aluminium, oxygen and silicon
Give one good example of cracking of hydrocarbons
Decane -> Octane + Ethene
What is the key difference between fractional distillation and cracking?
Fractional distillation involves separating existing compounds, not making new ones in a chemical reaction, which is what cracking does
What is reforming?
The conversion of straight-chain hydrocarbons into branched or cyclic hydrocarbons
Why is reforming used?
Hydrocarbons with a straight-chain burn less efficiently than cyclic or branched chains, which will then burn more smoothly in an engine
What is the process of reforming hydrocarbons?
Straight-chain hydrocarbons are heated with a catalyst, normally platinum.
What catalyst is usually used in reforming hydrocarbons?
Platinum
Give one good example of reforming of hydrocarbons
Pentane -> Cyclopentane + H2
What are the main products of the complete combustion of alkanes?
CO2 and H2O
What are the main possible products of the incomplete combustion of alkanes?
CO, Carbon particulates and unburned hydrocarbons
How are oxides of sulphur produced?
During the combustion of alkanes, sulfur impurities in the alkane form sulfur dioxide, and then can react with the atmosphere to form sulfur trioxide
What is the problem with oxides of sulfur?
They are acidic, and so when they dissolve in water in the atmosphere, they form sulfurous acid and sulfuric acid. This can cause environmental damage
How are oxides of nitrogen formed?
Very high temperatures, such as around spark plugs in cars, can cause the nitrogen molecules in the air to react with oxygen molecules
What are oxides of nitrogen represented by?
The formula NOx
What are the main oxides of nitrogen?
NO and NO2