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Alkane Soup!. Hydrocarbons. A molecule containing only carbon and hydrogen atoms. When we look at molecules, BLACK always means CARBON , and WHITE (and sometimes grey) means HYDROGEN . Hydrocarbons are the simplest organic molecules. Alkanes. Alkanes are a family of hydrocarbons
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Hydrocarbons • A molecule containing only carbon and hydrogen atoms. • When we look at molecules, BLACK always means CARBON, and WHITE (and sometimes grey) means HYDROGEN. • Hydrocarbons are the simplest organic molecules
Alkanes • Alkanes are a family of hydrocarbons • All single bonds – carbon is bonded to four other atoms • Alkanes are aliphatic – they form chains and non-aromatic rings (we’ll learn about aromatic molecules later) • Alkanes, like other hydrocarbon chains, form a homologous series • This means that adding a single carbon to the chain increases the number of hydrogens by a definite number • In the case of alkanes, # hydrogens = (2 x # carbons) + 2 • CnH2n+2
Fractional Distillation • Boiling points of alkanes increase with size, so refineries can use this property to separate crude oil into its components • Components: • < 20oC: Small gaseous alkanes, usually further refined or liquefied • 20-100oC: Slightly larger, used as solvents or further refinement • Up to 200oC: Straight-run gasoline – this gets refined and sold as common fuel • Up to 300oC: Large alkanes, used for kerosene and jet fuel • Up to 400oC: Larger alkanes, used as oil and diesel fuel • Remaining unboiled liquids are used as lubricating oils • Solid residues are used for asphalt, tar, and paraffin wax.
Uses of Alkanes • Methane (natural gas) • Butane lighters • Automotive and industrial lubricants • Vaseline (also a lubricant) • Commercial Gasoline (petrol) • Other Fuels (propane tanks) • Tar (used in asphalt) • Candle wax
How do we name them? • So, how did we come to call them methane, propane, butane, octane…? • IUPAC (International Union of Pure and Applied Chemistry) devised a system to name organic molecules • It uses a set of suffixes and prefixes to identify all organic molecules, from the simplest tothe ridiculously complex • It can get quite complex for verylarge molecules, which is whymany compounds still usecommon names
The Name • Think of naming a molecule as just like naming a person: Person: First Name(1) + Middle Names(2) + Family Name(3) Molecule: Branch Prefixes(2) + Root Name (1) + Family Suffixes(3) Alkanes all have the family suffix –ane.
IUPAC Nomenclature • There are lots of rules, but we’re going to learn them as we go. • When identifying a hydrocarbon, first find the longest chain of carbons that are bonded to each other (no breaks in the chain) • The longest chain ISN’T always the one going straight across! 3 8
Root Name • The longest carbon chain is known as the parent chain. The root name tells you how many carbons are in the parent chain. • Each prefix below refers to a number of carbons:
Methane Ethane Propane The First Six Alkanes Butane Hexane Pentane
Practice makes Perfect! • You need to practice naming lots of molecules! • Complete Alkane Worksheet • If you have any questions, make sure you ask me! • Do the following questions: (for homework) • P. 330 (#1, 2, 4) and p. 332 (all 4)