1# Organic Chemistry 2 3Organic compounds > 90% of known chemicals 4Carbon makes living systems possible 5 6Carbon forms 4 covalent bonds (4 valence pairs) 7Strong bonds with other non-metals 8Bonds with itself with single, double or triple 9Can form chains or rings 10 11Large number of compounds due to: 12-4 valence pairs 13- single / double / triple bonds 14- cyclic (ring) structures 15 16## Hydrocarbons 17 18Hydrocarbons - only carbon and hydrogen 19If all C-C bonds are single, the hydrocarbon is saturated 20 21Hydrocarbons 22- linear (aliphatic) 23- - saturated (all single C-C bonds) 24- - - alkane ($C_n H_{2n+2}$) 25- - unsaturated 26- - - alkene ($C_n H_{2n}$) 27- - - alkyne ($C_n H_{2n-2}$) 28- 29- cyclic (ring) 30- - saturated 31- - - e.g. cyclohexane 32- - unsaturated 33- - - e.g. benzene 34 35Carbon compounds with 4 branches are tetrahedral 36 37Compounds with $C-H$ are insoluble in water 38These compounds are almost non-polar due to similar electronegativities 39 40Only dispersion forces (between electrons on the outside of two molecules) hold each molecule together 41Dispersion forces increase with size (chain length), therefore MP and BP of straight molecules increases with length 42 43Branched molecules have lower MP and BP due to lower density (molecules are further apart due to their shape, so dispersion forces are weaker) 44 45Homologous series - formula for molecules (e.g. alkanes, alkenes, alkynes) where each member differs by some increment 46 47Structural isomers - same molecular formula, different configuration (structural formula) 48 49## Alkanes 50$$C_n H_{2n+2}$$ 51- Single bonds between carbon atoms 52- ending in *-ane* 53 54methane $CH_4$ 55ethane $C_2H_6$ 56propane $C_3H_8$ 57butane $C_4H_10$ 58pentane $C_5H_12$ 59hexane $C_6H_14$ 60$\dots$ 61 62Alkanes burn in oxygen forming $CO_2 + H_2O$ (oxidation / combustion reaction) 63 64Alkanes react with chlorine or fluorine (substitution reaction) - Cl or F replace H. Result is a haloalkane. 65 66## Alkenes 67 68$$C_nH_{2n}$$ 69 70- C-C double bond 71- ending in *-ene* 72 73methene $CH_2$ 74ethene $C_2H_4$ 75propene $C_3H_6$ 76butene $C_4H_8$ 77pentene $C_5H_10$ 78hexene $C_6H_12$ 79$\dots$ 80 81Alkenes burn in oxygen forming $H_2O + CO_2$. 82 83Alkenes react with hydrogen or a halogen (addition reaction) - additive breaks the double bond (catalyst is required). 84 85## Alkynes 86 87$$C_nH_{2n-2}$$ 88 89- C-C triple bond 90- ending in *-yne* 91 92Alkynes undergo combustion (oxidation) and addition reactions (same as alkenes). 93 94## Rules for naming HCs 95 961. Find longest chain of C atoms (incl. branches) 972. Start at end nearest a branch or double/triple bond 983. Name carbon atoms from end chosen 994. Branches end with *-yl* 1005. When there are $\ge$ 2 branches, number of C atom is indicated before each branch, and names are in alphabetic order. 1016. When there are $\ge$ 2 identical branches, *di-*, *tri-*, and *tetra-* are used. 102 103## Combustion 104$$C_xH_y+z0_2 \to\ xCO_n+{y \over 2}H_2O$$ 105**Complete** 106$z=x+{y \over 4}, n=2$ 107 108**Incomplete** 109$z={{2x+y} \over 4}, n=1$ 110$z={{x+y} \over 4}, n=0$ 111 112## Functional groups 113 114Atom(s), or a bond, which give a properties to an organic molecule. 115 116### Alcohols / hydroxyls 117 118- ---OH functional group 119- ends in *-ol* 120- alcohols have multiple isomers 121- combustible with oxygen 122- BP and MP are affected by H-bonding 123- **H-bonds are represented by dotted lines** 124 125### Carboxylic acids / carboxys 126 127- ---COOH functional group 128- ends in *-oic acid* 129- first portion of name (e.g. **methan**oic acid) refers to **total** number of carbons 130- weak acids (proton from O is donated) 131- high BP 132 133### Esters 134- carboxylic acid reacts with alcohols to form esters (condensation / esterification) 135- catalyst is $H_2SO_4$ 136- low boiling points 137- intermolecular bonding is dipole-dipole and dispersion rather than H-bonding 138- ends in *-oate*