Organic Chemistry Flashcards
Define organic compounds
Compounds containing carbons (excluding oxides and carbonates)
Define functional group
A functional group is an atom or group of atoms in an organic molecule which is responsible for characteristic reactions of that molecule
Define homologous series
A homologous series is a family of compounds that all contain the same functional group and can be represented by the same general formula
What is the general formula of alkanes?
CₙH₂ₙ₊₂
What are the first five prefixes of organic molecules?
Meth-
Eth-
Prop-
But-
Pent-
Define molecular formula
The actual number of atoms of each element in a compound
Define empirical formula
The simplest ratio of atoms of each element in a compound
Define general formula
A general formula is a type of empirical formula that represents the composition of any member of an entire class of compounds
Define structural formula
This shows the unique arrangement of the atoms in a molecule without showing every bond
Define displayed (graphical) formula
This shows every atom and every bond in a molecule
Define skeletal formula
This shows the carbon chain skeleton of a compound with all the hydrogen atoms removed leaving just the functional groups attached to it
What is an alkyl group?
They are derived from alkanes but with a H missing
Often attached to organic molecules
What is the general formula of cycloalkanes?
CₙH₂ₙ
What is the general formula of haloalkanes?
CₙH₂ₙ₊₁X
(Where X = F, Cl, Br, I, At)
List the naming prefixes for haloalkanes
fluoro-
chloro-
bromo-
iodo-
Name the functional group and name suffix for the homologous series alcohols
Functional group = -OH
Suffix = -ol
Name the functional group and name suffix for the homologous series aldehydes
Functional group = -C=O (has to be on end)
Suffix = -al
Name the functional group and name suffix for the homologous series ketones
Functional group = -C=O
Suffix = -one
Name the functional group and name suffix for the homologous series carboxylic acids
Functional group = -COOH
Suffix = -oic acid
Name the functional group and name suffix for the homologous series nitriles
Functional group = -C≡N
Suffix = -nitrile
Name the functional group and name suffix for the homologous series amines
Functional group = -NH₂
Suffix = -amine
Define isomerism
Molecules with the same empirical formula but with their atoms arranged differently
Define structural isomerism and give the three subtypes
Compounds with the same molecular formula but different structures
- Chain
- Positional
- Functional group
Define stereo isomerism and give the two subtypes
Compounds with the same molecular and structural formula but the bonds are arranged differently in space
- Geometric
- Optical
Define chain isomerism
Compounds with the same molecular formula but the carbon chains are different
Define position isomerism
Compounds with the same molecular formula but the functional groups are in different positions on the carbon chain
Define functional group isomerism and give examples
Compounds with the same molecular formula but containing different functional groups
- Alkenes & cycloalkanes
- Alcohols & ethers
- Aldehydes & ketones
What happens to the melting and boiling point of hydrocarbons as chain length increases?
As chain length increases, so too does melting and boiling point:
- Mr ↑
- No of electrons ↑
- Van der Waals forces ↑
How does branching effect the melting and boiling point of hydrocarbons?
As branching increases, the melting and boiling point decrease:
- As branching ↑
- Molecules don’t pack together as closely
- So Van der Waals forces weaker
Define geometric isomerism
Compounds with the same molecular and structural formula but a different arrangement of the bonds
How can Z-isomers and E-isomers be differentiated?
E = Opposite
Z = Together
Why does stereoisomerism occur?
The carbon-carbon double bond prevent the carbon atoms and anything else attached from rotating
What is crude oil?
- A fossil fuel
- World’s major source of hydrocarbons
- Raw material
- Often located underneath the sea bed
What are the two main problems with crude oil?
- It is a mixture
- It produces too many long hydrocarbons and not enough short hydrocarbons compared to consumer demand
How are the hydrocarbons in crude oil separated?
Fractional distillation
Describe the distribution of hydrocarbons in a fractionating column
At the top:
- Small molecules
- Low b.p
- Very volatile
At the bottom:
- Large molecules
- High b.p
- Not very volatile
Describe what happens during fractional distillation
- Crude oil heated to about 400 degrees C
- Oil vapours enter the bottom of the fractionating column and start to rise up
- As the vapours rise, they cool down and condense back to liquid at different levels depending upon their boiling point
In order to obtain purer products, the fractions can be further processed by secondary distillations
Define cracking
Cracking is the process of taking larger, less useful hydrocarbon molecules and breaking them down to form smaller, more useful molecules
Give a word equation for cracking
Bigger alkanes → smaller alkanes + alkenes (+hydrogen)
Describe thermal cracking
- Needs a high temp (800C) and high pressure (700 kPa)
- Produces a high % of alkenes
- Involves a free radical mechanism
Describe catalytic cracking
- Uses a high temp (450C) and slight pressure
- Zeolite catalyst
- Produces mainly branched chain alkanes used as motor fuels
Why are alkanes almost non-polar?
- Electronegativities of C and H are very similar
- Resulting Van der Waals are very weak
Why are alkanes insoluble in water?
Water molecules held together by H-bonds, which are much stronger than the VdW between alkane molecules
Describe the reactivity of alkanes
Not very reactive. Do not react with acids, bases, oxidising or reducing agents.
Because:
- C-H & C-C bonds are much stronger than other single covalent bonds
- C-C bonds are non-polar and C-H bonds are virtually non-polar
Give the word equation for the complete combustion of alkanes
alkane + oxygen → carbon dioxide + water
Give the word equation for the incomplete combustion of alkanes
alkane + oxygen → carbon monoxide + carbon + water
(carbon monoxide and/or carbon)
Why is carbon monoxide dangerous?
It is a poisonous gas but is completely colourless and odourless
What are the dangers of particulates?
Particulates of C and CO can exacerbate asthma and cause cancer
What causes acid rain?
Sulphur dioxide formed when burning fossil fuels containing sulphur impurities