Topic: Alkanes Do Now: Draw the possible bonds a single carbon atom can have if it has a bonding capacity of 4

Alkanes Homologous series of saturated hydrocarbons Release energy when burned CnH2n+2 – all have this general formula CH4 H H–C–H H C2H6 H H H–C–C–H H H

Saturated hydrocarbons: organic compounds containing only Single bonds – can’t add any more Hydrogens

Properties of Alkanes Low Reactivity Except readily undergo combustion (fuels) Nonpolar – don’t dissolve well in water Low melting & low boiling points both increase with molecular mass High vapor pressures

Properties of Alkanes Change systematically with # of C’s As # of C’s increases, boiling point increases molecules get heavier so harder to change into gas phase

Which property is generally characteristic of an organic compound? Low melting point High melting point Soluble in polar solvents Insoluble in nonpolar solvents Correct response = A

Which of the following compounds has the highest boiling point? Correct answer = D nonpolar coval cmpd: bp depends on strength of van der Waals interactions van der Waals forces ↑ as size of molecule ↑ bigger molecule = bigger electron cloud

Alkanes (CnH2n+2) C3H8 H H H H–C–C–C–H CH3CH2CH3 Chemical Formula Structural Formula Condensed Structural Formula

straight-chain alkane H H H H H–C–C–C–C–H Or CH3CH2CH2CH3

Naming straight-chain Alkanes Name: describes molecule so can draw it all alkanes have the suffix –ane prefix: tells # of C’s

C5H12 C4H10 C3H8 C2H6 Meth + ane CH4 Name Formula Ethane Propane Dec 9 Non 8 Oct 7 Hept 6 Hex 5 Pent 4 But 3 Prop 2 Eth 1 Meth # of C atoms Prefix C5H12 C4H10 C3H8 C2H6 Meth + ane CH4 Name Formula Ethane Propane Butane Pentane

Naming Branched-Chain Alkanes goal of name is to describe molecule so you can draw it

Naming branched-chain alkanes Find longest continuous chain of C atoms - Bends don’t matter!

2. base name derived from # C’s in continuous chain 9 carbon chain = nonane

triethyl, methyl, propyl 3. Branches named first and in alphabetical order * to name branches, count # C atoms & add “yl” to prefix name * If more than one of same type of branch - use di, tri, etc. propyl ethyl ethyl methyl ethyl triethyl, methyl, propyl

Assign number to Branches based on longest carbon chain Assign number to Branches based on longest carbon chain * you want numbers to add up to the lowest # propyl ethyl ethyl 6 3 5 4 7 2 8 methyl 1 9 ethyl 4, 4, 5, 5, 6 = add up = 24

Assign number to Branches based on longest carbon chain Assign number to Branches based on longest carbon chain * you want numbers to add up to the lowest # propyl ethyl ethyl 6 7 4 5 3 8 2 methyl 9 1 ethyl 4, 5, 5, 6, 6 = add up = 26

2. triethyl, methyl, propyl 4. Put it all together 4,4,6-triethyl 5-methyl 5-propyl nonane propyl ethyl ethyl 6 3 5 4 7 2 1. nonane 8 methyl 1 2. triethyl, methyl, propyl 9 ethyl 3. 4, 4, 5, 5, 6

1 2 3 H 2-methyl propane H–C–H No because if methyl was anywhere else it wouldn’t be propane H H–C–H H H H–C–C–C–H H H H 1 2 3 Methyl propane C4H10 CH3CH(CH3)CH3 Longest continuous chain has 3 carbon atoms – propane

Longest continuous chain has 5 C atoms: pentane Branch: 1 carbon = methyl Branch: 12 carbon = ethyl Branch located at C-2 and 3 3-ethly 2-methyl pentane C8H18 CH3CH(CH3) CH(CH2CH3)CH2CH3 H H–C–H H H H H–C–C–C–C–H H H H 6 5 4 3 2 1

Branched-chain alkanes Beginning with butane, C4H10, there is more than 1 way to arrange the atoms H H–C–H H H H–C–C–C–H H H H ISOMERS