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

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Presentation on theme: "Topic: Alkanes Do Now: Draw the possible bonds a single carbon atom can have if it has a bonding capacity of 4."— Presentation transcript:

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

2 Alkanes Homologous series of saturated hydrocarbons Release energy when burned C n H 2n+2 – all have this general formula CH 4 H H–C–H H C 2 H 6 H H H–C–C–H H H

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

4 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

5 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

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

7 A.CH 4 B.C 2 H 6 C.C 3 H 8 D.C 4 H 10 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 bp depends on strength of van der Waals interactions van der Waals forces ↑ as size of molecule ↑ van der Waals forces ↑ as size of molecule ↑ bigger molecule = bigger electron cloud bigger molecule = bigger electron cloud

8 Alkanes (C n H 2n+2 ) C 3 H 8 H H H H–C–C–C–H H H H CH 3 CH 2 CH 3 Chemical Formula Structural Formula Condensed Structural Formula

9 straight-chain alkane C 4 H 10 H H H–C–C–C–C–H H H Or CH 3 CH 2 CH 2 CH 3

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

11 10Dec 9Non 8Oct 7Hept 6Hex 5Pent 4But 3Prop 2Eth 1Meth # of C atoms Prefix C 5 H 12 C 4 H 10 C3H8C3H8 C2H6C2H6 Meth + ane CH 4 NameFormulaEthanePropane Butane Pentane

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

13 Naming branched-chain alkanes longest continuous chain 1.Find longest continuous chain of C atoms - Bends don ’ t matter!

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

15 3. 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. ethyl methyl propyl triethyl, methyl, propyl

16 Assign number to Branches Assign number to Branches based on longest carbon chain * you want numbers to add up to the lowest # ethyl methyl propyl , 4, 5, 5, 6 = add up = 24

17 Assign number to Branches Assign number to Branches based on longest carbon chain * you want numbers to add up to the lowest # ethyl methyl propyl , 5, 5, 6, 6 = add up = 26

18 4. Put it all together ethyl methyl propyl , 4, 5, 5, 6 2. triethyl, methyl, propyl 1. nonane nonane4,4,6-triethyl 5-methyl 5-propyl

19 H H–C–H H H–C–C–C–H H H H 2-methyl propane No because if methyl was anywhere else it wouldn’t be propane propane Longest continuous chain has 3 carbon atoms – propane Methyl propane C 4 H 10 CH 3 CH(CH 3 )CH 3

20 H H–C–H H H H H–C–C–C–C–H H H H H–C–H H Longest continuous chain has 5 pentane C atoms: pentane methyl Branch: 1 carbon = methyl ethyl Branch: 12 carbon = ethyl 2 and 3 Branch located at C-2 and 3 3-ethly 2-methyl pentane C 8 H 18 CH 3 CH(CH 3 ) CH(CH 2 CH 3 )CH 2 CH 3

21 Branched-chain alkanes Beginning with butane, C 4 H 10, there is more than 1 way to arrange the atoms H H–C–H H H–C–C–C–H H H H ISOMERS


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