Organic Chemistry Flashcards
What is the general formula for alkanes?
-C nH2n+2
Name the first four alkanes in the homologous series.
-methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀).
What is fractional distillation used for?
- to separate the different hydrocarbons in crude oil into fractions, each containing molecules with a similar number of carbon atoms.
What are the main fuels produced from crude oil?
-petrol, diesel oil, kerosene, heavy fuel oil, and liquefied petroleum gases (LPG).
What products are made by the petrochemical industry from crude oil?
-solvents, lubricants, polymers, and detergents.
What is the result of the complete combustion of a hydrocarbon?
- carbon dioxide (CO₂) and water (H₂O), along with energy.
What is cracking
- the process of breaking down large hydrocarbons into smaller, more useful molecules like alkanes and alkenes.
How are alkenes different from alkanes?
-Alkenes are more reactive than alkanes because they contain at least one double bond between carbon atoms.
What are the two main methods of cracking hydrocarbons?
-catalytic cracking and steam cracking.
What are alkenes used for?
-to produce polymers and as starting materials for the production of many other chemicals.
What are hydrocarbons?
-molecules made up of hydrogen and carbon atoms only
how is crude oil formed?
- it is formed over millions of years from the remains of sea creatures called plankton which were buried in mud.
-it is a mixture of molecules called hydrocarbons
what does viscosity tell us?
-the thickness of a fluid
-longer hydrocarbon molecules have higher viscosity while shorter hydrocarbons have lower viscosity
what does flammability tell us?
-how easily a hydrocarbon combusts (burns)
-short chain hydrocarbons are extremely flammable
what does boiling point tell us?
-the temperature a liquid turns into a gas.
-short chain hydrocarbons have low boiling points while long chain carbons have high boiling points
what are the steps of fractional distillations?
-firstly, the crude oil is heated at a very high temperature
-this causes the crude oil to boil - all of the hydrocarbons evaporate and turn into gas
-the crude oil vapour is now fed into the fractional distillation column
-the column is hotter at the bottom and cooler the top
-the hydrocarbon vapours now rises up the column and condenses at their boiling points
-the liquid fraction is then removed
-the remaining hydrocarbon fuels condense continue rising up the column and condense at their own boiling points.
key point for fractional distillation process
-very long chain hydrocarbons have very high boiling points that are removed from the bottom of the column
-very short chain hydrocarbons have very low boiling points and these do not condense and are removed from the top of the column as gases.
how are fractions used for the petrochemical industry?
-as feedstock which is a chemical that is used to make other chemicals
why do long chain hydrocarbons not make good fuels?
-they are not very flammable
what are the conditions required for catalytic cracking?
-high temperature and a catalyst
what are the conditions required for steam cracking?
-high temperature and steam
what is the structure of alkenes
-double covalent bond between two carbon atoms
why are alkenes useful molecules?
-they are used to make chemicals called polymers
-they are also used as starting materials for other useful chemicals as well
how do we test for alkenes?
-we test for alkenes using bromine water which is orange
-we shake our alkene with bromine water and the bromine water turns colourless
What are alkenes?
-hydrocarbons with a double carbon-carbon bond.
What is the general formula for alkenes?
-𝐶𝑛𝐻2𝑛
What are the first four alkenes in the homologous series?
- ethene (C₂H₄)
- propene (C₃H₆)
- butene (C₄H₈),
- pentene (C₅H₁₀).
What is the functional group in alkenes?
- the carbon-carbon double bond (C=C).
How do alkenes react in combustion reactions?
- Alkenes react with oxygen in combustion reactions, but they tend to burn with smoky flames due to incomplete combustion.
why are alkenes called unsaturated molecules ?
-alkenes have two fewer hydrogen atoms than the alkane with the same number of carbon atoms
what does ‘functional group’ mean?
-the part of a molecule that determines how it reacts
what kind of series are alkenes?
-homologous series
why does combusting an alkene produce unburnt carbon particles?
-incomplete combustion
describe the reaction between hydrogen and alkenes?
-this is called hydrogenation
-this reaction requires a temperature of around 150 degrees
-we need to use a nickel catalyst to speed up the chemical reaction
-in this reaction, the two hydrogen atoms add across the double bond.
-the carbon to carbon double bond is converted into a carbon to carbon single bond
-reacting an alkene with hydrogen produces an alkane
what is an alkene?
-unsaturated hydrocarbon that contains a double carbon bond
describe the combustion of alkenes?
-they burn with smoky flames due to incomplete combustion.
what is an alcohol?
-organic compound that contains an -OH functional group
state characteristics of methanol,ethanol,propanol and butanol
-dissolve in water to form a neutral solution
-react with sodium to form hydrogen
-burn in oxygen
-react with carboxylic acids in presence of acid catalyst to form esters
oxidation of the alcohols lead to…?
-carboxylic acids
what are some uses of alcohols?
-fuels
-solvents
-drinks
how is ethanol produced? + conditions
-Ethanol can be produced by fermentation of sugar with yeast, using renewable
sources.
● Conditions: about 35°C, anaerobic (without oxygen) and yeast enzyme catalyst
● Sugar → ethanol + carbon dioxide
what are carboxylic acids?
-organic compounds that contain a COOH functional group
state the 4 characteristics of carboxylic acids
-dissolve in water to form an acidic solution ( contains H (+) ions )
-react with metal carbonates to form carbon dioxide
-react with alcohols with an acid catalyst to produce esters
-react with metals to give off hydrogen gas
what type of acid is carboxylic acid?
-a weak acid
why are carboxylic acids weak acids?
-they are partially dissociated in water, thus the pH of a carboxylic acid in solution is not as low as a solution of strong acid of the same concentration
what is an ester and how is it formed? what is characteristic about this class of compounds?
-an organic compound containing a -COO functional group formed from carboxylic acid and alcohol in the presence of a sulfuric acid catalyst
-they have a fruity smell
What is a polymer? How do molecules containing C=C bond form polymers?
-a polymer is a long chain molecule which is made by lots of smaller molecules joining together
-C=C bonds open up and many smaller molecules (monomers) join together to form a polymer chain .
-it is called an “addition polymerisation” reaction
Give 3 examples of addition polymers and their uses
-Polythene - plastic bags
-(poly)tetraflouroethene (PTFE) - teflon surfaces, non stick kitchenware
-(Poly)chloroethene (polyvinylchloride, PVC) -water pipes
what is a repeating unit of a polymer? + how to draw it
-a smallest structure which, upon numerous translations, yields the structure of the polymer
-in addition polymers : to draw it, take a monomer, change C=C to C-C and show additional single bonds extending away from these carbons
What is a condensation polymer? How is it made?
-There are 2 main groups - name them and give industrially relevant examples.
-a polymer made in condensation polymerisation
-in this reaction, many molecules join together, the polymer is formed, but also a small molecule is released
-Polyesters e.g terylene
-Polyamides e.g Nylon
What is an amide bond?
-An amide bond is similar to the ester bond, with O replaced by N
-(C=O)-NH(2)
-just like an ester , it contains the C=O group
what is an amino acid?
-an organic compound that contains both a carboxylic acid functionality ( COOH) and a amine functional group (-NH(2))
How do amino acids make proteins ? What are polypeptides?
-By numerous condensation polymerisation reactions ; proteins are polymers made of amino acids (monomers)
-polypeptides are also made by condensation polymerisation of amino acids, but are shorter than proteins. One could think about proteins as a product of many polypeptide chains bonded together
What are carbohydrates?
-organic molecules made of C,H and O
-they are biologically relevant, e.g starch and cellulose
-both of these are polymers made of glucose (other carbohydrate) monomers
-their structures differ in the way the glucose molecules are joined together
What is DNA? Describe its role and structure
-DNA ( deoxyribonucleic acid) is a material that makes up chromosomes - cell structures that store genetic information.
-DNA is made of two polymer chains that are held together in a double helix
-each polymer chain can be made from 4 different monomers - nucleotides.
