Organic Compounds Flashcards
How is methane produced?
By anaerobic bacterial decomposition of either animal waste or vegetation
Why is the concentration of methane a cause of concern?
Global warming
The boiling points of propane and dodecane are -42 and 216 respectively. Explain why high molecular mass alkanes have high boiling points?
Stronger intermolecular bonds
Distinguish between saturated and unsaturated hydrocarbons
Saturated hydrocarbons - only single bonds - has max no of hydrogens atom can have
Unsaturated - contains at least one double/triple bond, doesn’t have max amount of hydrogens
How many pi electrons are there in benzene?
6
What is the distribution of pi electrons like in benzene?
Delocalised
Give evidence to support the fact that pi electrons are delocalised in benzene molecule
All c-c bonds are of same energy/length
All c-c bonds in benzene are intermediate between single and double in energy
What is organic chemistry?
Study of compounds of carbon other than carbon monoxide, carbon dioxide, carbonates and hydrogencarbonates]
What is a functional group?
It’s an atom or group of atoms which is responsible for the characteristic properties of a series of organic compounds
What kind of bonds do saturated organic compounds have?
Sigma, end on overlap of atomic orbitals
What kind of bonding do unsaturated compounds have?
1 sigma with other bonds of pi type - sideways overlap of p orbitals
What are hydrocarbons?
Compounds that contain carbon and hydrogen only
What is a homologous series?
A family of organic compounds with the same general formula, similar chemical properties and successive members differing by CH2
What hydrocarbon when exposed to air forms an explosive mixture?
Methane
How are hydrocarbons formed?
They are naturally occurring and have been formed in the earth over millions of years, eg crude oil
What is the bond angle of a tetrahedral shaped molecule?
109.5 degrees
What are the three types of tetrahedral carbon compounds?
Alkanes, alcohols and chloroalkanes
What hydrocarbons are saturated?
The ones that contain single bonds - alcohol, alkanes and chloroalkanes
What is the functional group of alkanes?
c-c
carbon single bonds
What sort of reactions do alkanes undergo?
Substitution reactions
Give two uses of alkanes
Petrol - 5-10 atoms c atoms
Kerosene [jet due, and central heating fuel]
LPG [liquefied petroleum gas] made up of propane and butane
What are isomers?
Compounds with the same molecular formula but different structural formula
How do isomers differ?
Physical properties eg, boiling points
What is an alkyl group?
It’s an alkanes molecule from which a hydrogen atom has been removed
CH3 - methyl
C2H5 - ethyl
What are alcohols?
Similar to alkanes but with a hydrogen replaced by OH
What is the functional group of alcohols?
Hydroxyl group
OH
How do you write molecular formula of alcohols?
Alkyl group + OH
What is a primary alcohol and give an example
When the carbon attached to the hydroxyl group is attached to one other carbon
Eg, propan-1-ol
What are secondary alcohols?
When the carbon attached to the hydroxyl group is attached to two other carbons
Eg, propan-2-ol
What are tertiary alcohols?
When the carbon attached to the hydroxyl group touches three other carbons
Eg, 2-methylpropan-2-ol
What must you always do when naming alcohols?
Indicate position of hydroxyl group
What changes alcohols chemistry drastically from corresponding alkanes?
Hydroxyl group
Boiling point of alcohols?
Higher than corresponding alkanes
The hydroxyl undergoes hydrogen bonding which results in them having very strong bonds. As a result, it takes more energy to break apart bonds = higher
Solubility of alcohols?
It changes as length of carbon chain increases. The OH group is highly polar and if the chain is short, it forces the non polar part [alkyl group] to dissolve in polar substances such as water. If chain becomes too long, the OH group is insignificant and therefore dissolves in non polar substances instead
What shape is the functional group of alcohols?
V shaped
Explain fermentation
Fruits with glucose have yeast added to them which contains catalyst zymase. Zymase converts glucose into ethanol and carbon dioxide as a result.
Why does fermentation alone not produce drinks greater than 12% v/v
Once ethanol reaches this percentage, it kills yeast - stops fermentation
How do you increase alcohol concentration and give an example
Fermented liquids are distilled eg, wine is distilled to brandy
What are the uses of ethanol?
Alcoholic drink [consumption], solvent [perfumes]
Why is ethanol a good solvent?
Due to hydrogen bonding
Describe hydrogen bonding in alcohols
Oxygen - partial negative charge [more electronegative]
Hydrogen - partial negative charge
Oxygen in hydroxyl group in one molecule attracts hydrogen in hydroxyl group on neighbouring molecule
This forms strong hydrogen bonds
Why do ethanol and water mix completely in alcoholic drinks?
Hydrogen bonds form between hydroxyl groups in ethanol and hydroxyl groups in water
What are chloroalkanes?
An alkane with one or more of its hydrogens replaced by chlorines
What’s another name for chloroform and give a use
Trichloromethane
was used as an anaesthetic
Are chloroalkanes soluble in water?
No, carbon-chlorine bond is polar but not polar enough to make a different to physical properties
Boiling point in chloroalkanes
Low boiling points but higher than corresponding alkanes
What state are chloroalkanes in room temperature?
Liquids
What two chloroalkanes are gases at room temp?
Chloromethane, chloroethane
States at room temperature of alkanes
Up to C4 - gases
Next 12 - liquids
Rest - solids
Why does boiling point of chloroalkanes increase with carbon chain?
Stronger van der waals forces
Uses of chloroalkanes and why?
Used as solvents - lack of polarity, readily dissolve grease and oil which are insoluble in water
Give a damaging hydrocarbon in chloroalkanes
Chloromethane - damage to ozone layer
Name the carbon compounds that are planar
Alkenes, alkynes, aldehydes, ketones, carboxylic acids, esters, aromatic compounds
Shape of alkenes
Both tetrahedral and planar
Tetrahedral - everywhere but where double bond is
Are alkenes saturated or unsaturated?
Unsaturated - double bond
What reactions do alkenes undergo?
Addition reactions