Organic chemistry BC Science Probe 10 Section 8.3
Organic Chemistry • Organic means living • Hydrocarbons contain hydrogen and carbon atoms • Organic Chemistry is the study of carbon chemicals that are natural and artificial. • The bonding in hydrocarbons is covalent so bonding between molecules is weak. • The structure is molecular.
Percentage of Carbon • To be considered organic, a compound must have a high percentage of carbon by mass: • To calculate the percentage of carbon, you take the mass of carbon in the molecule divided by the mass of the whole molecule and multiply it by 100% • If it is higher than 50%, it’s organic!
Alkanes CnH2n+2 • The bond between atoms are all single. • The bonds between atoms are strong but the bonds between molecules are weak. CARBON CARBON UNREACTIVE BONDS CARBON HYDROGEN
Properties • Good fuels: - lots of heat energy made - COMPLETE COMBUSTION H2O + CO2 - Short chains are best (cleaner + less energy to break) • Do not dissolve or react with water or reactants dissolved in water: - no energy to break the unreactive C-C or C-H bonds.
H H H C C H H H H H H C H Examples: Methane CH4 Ethane C2H6
H H C C H H Alkenes CnH2n • C=C is more reactive than C-C • The molecule is unsaturated and the double bonds allow addition polymerisation. Ethene C2H4
Alcohols CnH2n+1OH • Functional group= OH CARBON OXYGEN MORE REACTIVE THAN: C-C C-H HYDROGEN OXYGEN
H H C C H H H H O H C H Examples: H Methanol CH3OH O H Ethanol C2H5OH
Physical Properties • Forces between molecules are stronger than between alkane molecules so alcohols are liquid at room temp. • Alcohol molecules have a tendency to stick together because they have OH, like water but not as much. • Short chains mix with water. • Long chains are oily because more CH than OH.
Chemical Properties • CH part burns CO2 + H2O • React with Na like water but slower: OH reacts and CH is inert. sodium + ethanol sodium ethanoxide + water
Organic Acids (Carboxylic) CnH2n-1COOH • Functional group= COOH • Made by oxidising Alcohols: 1. Alcohol heated with catalyst 2. Reflux condenser used to vapours are not lost but drip back into the solution. 3.Organic acid collected. • The oxidation reaction is used in breathalyser tests • ethanoic acid (in water) H+ and ethanoate ions ions This is reversible as the ions react and reform ethanoic acid.
Acids Acid + Water Hydrogen ions + Other ions HCl + H2O H+ ions + Cl- ions
REACTIVITY Alcohols Alkenes Alkanes
H H C C H H H O H H H H H H H H C C C H O H C C C H O H H H H Ethanol C2H5OH Ethane C2H6 Ethanoic Acid CH3COOH Ethene C2H4
Esters Organic Acid + Alcohol Ester + Water This is a CONDENSATION REACTION as a molecule of water is lost. Alcohol loses OH and Acid loses H = H2O This is HYDROLYSIS because water is used to split the ester molecules. Sped up when heated &/or acid/alkali added
O C O ESTER LINK • Fruits • Plasticisers PVC • Soaps • Fats • Vegetable oils • Polyester • Laminates MORE THAN ONE ESTER LINK
Esterification Ester + Alcohol Pure Ester Sample + Impurities Esterification is this reaction when heated with some concentrated sulphuric acid to make a pure Ester. • Heated + reflux condenser • Keep heating after reflux + impurities condense and out.. • Separating method: shaken alcohols, acids react with aqueous reagents and dissolve but Ester does not. • Calcium chloride crystals absorb moisture dry Ester • Heat, only Ester evaporates and then condenses PURE DRY ESTER
Fats and Oils • Fats and Oils have more than one Ester link in a single molecule. • Fats and Oils release 5 x more energy when oxidised than carbs. They are better energy store. Fats Acids + Alcohol Fats Fatty Acids + Glycerol (Alcohol)
FATTY ACID FATTY ACID FATTY ACID O GLYCEROL C H H O O O H-C-O-C-CH2-CH2..-CH3 H-C-O-C-CH2-CH2..-CH3 H-C- H-C- H-C- H-C- ESTER LINK
MARGARINE: Nickel catalyst Vegetable oils Margarine Unsaturated Saturated ( Heart Disease) This is HYDROGENATION Hardening vegetable oils is cheaper than butter but it is just as harmful.
CIS Fats: Occur naturally is unsaturated fatty acids Unsaturated 2 parts of the chain on the same side of the double bond. Omega 3 Fatty Acid POLYUNSATURATE Found in fish Double bonds on every 3rd Carbon Unsaturated, good for joints C-C-C=C-C-C=C-C-C=C Omega 6 Fatty Acid POLYUNSATURATE Found in plant oils Double bonds on every 6th Carbon C-C-C-C-C-C=C-C-C-C-C-C=C Trans Fats: More solid than CIS fats Structure like saturated fatty acid Heart disease Unsaturated 2 parts of the chain on opposite sides of the double bond 3 x Omega6 : 1x Omega3 Essential part of a balanced diet