Organic Chemistry Chapter 18 worgo.mp3

Introduction Organic = from living organisms Organic chemistry is about molecules found in living organisms or produced by living organisms. This chemistry of all carbon compounds (except very small chemical compounds like CO 2 and carbonates). Carbon as an element

Huuuuuuge variety of C compounds Bonds with itself, and other atoms Covalently Forms chains or rings or both Single or double or triple bonds Can be thousands of atoms long

Introduction Most organic compounds also contain H = hydrocarbon. Can have O, N, F, Cl, Br, I, S Even metals Eg? Fe, Mg Reactive part of the molecules = functional group Put into families depending on their functional group Homologous series = compounds belonging to the same family and only differing by –CH2 Stop at 2:15

Types of Formulas for Organic Molecules Molecular (general) formulae (ex. CH 4 ) ◦ Rarely used in organic chemistry ◦ Tells us which elements are present and how many ◦ Does not indicate structure (e.g. What structure does C 3 H 8 O have?) ◦ Still used when writing equations involving hydrocarbons (molecules made up of H and C).

Three dimensional formulae Methane: ◦ CH 4

Structural formula Displayed and condensed form Examples ◦ Butane  CH 3 -CH 2 -CH 2 -CH 3  C 4 H 10 ◦ Ethene  C 2 H 4  CH 2 =CH 2

Naming organic molecules Length of chain: ◦ This is shown by the prefix at the start and it is the same no matter which type of organic molecule it is. Alkanes: ◦ CH 4 = methane ◦ C 2 H 6 = ethane ◦ C 3 H 8 = propane ◦ C 4 H 10 = butane ◦ C 5 H 12 = pentane ◦ Hexane ◦ Heptane ◦ Octane ◦ Nonane ◦ Decane

Naming Organic Compounds 1. Find the longest carbon chain so you can name the stem (eg. 3 C = prop) 2. Identify where the functional groups are on the chain using the lowest number posible (may not be left to right) 3. Identify the functional group names and whther they go before or after the stem name (eg Cl = chloro- ; -OH = -ol) 4. Prefixes and suffixes go in alphabetical order

For example Step 1. Four carbons long = -but- Step 2. Number the carbons from right to left for the lowesr numbers Step 3. Chloro on carbon 1 and bromo on carbon 3 3-bromo-1-chlorobutane

Unsaturated hydrocarbons For alkenes, the position of the C=C can vary. This is shown by the number in the middle of the name. Examples: ◦ But-1-ene, CH 2 =CHCH 2 CH 3 ◦ But-2-ene, CH 3 CH=CHCH 3 ◦ But-3-ene doesn’t exist, it is the same as But-1-ene The number comes from where the double bonds starts. Hex-1,2,3-ene, draw these

Branched chains Some hydrocarbon chains have branches. ◦ Methyl, -CH 3 ◦ Ethyl, -C 2 H 5 The branches are included in the names. 1.2-methylbutane 2.2,2-dimethylpropane 3.2,3-dimethylhexane 4.2,3-dimethylbut-2-ene

Structural Isomerism Isomer: same molecular formula, different structural formula. Using molymods, how many different structures can you make with 4Cs and 10Hs. Note that you cannot bend or twist one to become another. You need to take one apart and put it back together to make the other.

C 5 H 12 - Pentane What are the isomers of pentane?

Structural Isomers of Pentane

Physical differences Vary slightly due to different intermolecular attractions. Intermolecular forces are stronger the closer molecules can get to each other. Straight chains can get closer to one another. More branches = lower boiling point No chemical differences

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