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Unit 2

Unit 2. Introduction to Hydrocarbons. Differences between organic and inorganic compounds:. 1. Organic compounds are mostly covalent molecules where most inorganics are ionic 2. Most organics don’t dissolve in water and most inorganics do

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Unit 2

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  1. Unit 2 Introduction to Hydrocarbons

  2. Differences between organic and inorganic compounds: 1. Organic compounds are mostly covalent molecules where most inorganics are ionic 2. Most organics don’t dissolve in water and most inorganics do 3. Organic compounds decompose on heating easier than inorganics 4. Organic reactions are much slower (min, hours, days) than inorganic reactions (seconds)

  3. Fun Facts (Don’t have to Copy) • More than 18 Million organic compounds [with 10,000 new ones discovered each year] • 1.7 Million inorganic compounds so about 85% of compounds are organic

  4. 2 Reasons for the abundance of organic compounds: • Carbon atoms bond to each other to form long chains(up to 200 carbons) • Catenation – the ability of an element to bond to itself • The same number of carbon atoms can rearrange to form different structures (isomers) • Isomer – compounds with the same molecular formula but different structures

  5. Isomer Example • C5H12 C C • -C-C-C-C-C- -C-C-C-C- -C-C-C- C

  6. How Carbon Bonds • C ground state is 2s22p2 but bonds as *2s12p3 giving 4 sp3 hybrid orbitals • Hybrid orbitals – orbitals of equal energy formed by mixing orbitals of different energies • Hybridization – the mixing of orbitals of different energies to give orbitals of equal energy

  7. How Carbon Bonds • Carbon’s 4 covalent bonds form a tetrahedron (109.5° bond angle)

  8. Hydrocarbons! • Hydrocarbons – compounds containing only hydrogen and carbon • Alkanes – hydrocarbons that have all C-C single bonds

  9. Naming

  10. Naming • *Know roots and endings* •  Each step, you add a CH2 group • Homologous Series – a series of compounds where each member differs from the next by a constant unit (CH2) • Members are called homologous • Since alkanes are homologous – we can write a General Formula = CnH2n+2

  11. Naming • Alkanes are Saturated Hydrocarbons – hydrocarbons where each C has 4 single covalent bonds (no more atoms can be added)

  12. Alkenes • Alkenes – hydrocarbons with one C=C double bond – sp2 hybridization on the 2 C atoms in the double bond. • Ethene C=C CH2CH2 C2H4 • Propene C=C-CCH2CHCH3C3H6 • Butene C=C-C-C CH2CHCH2CH3 C4H8 • OcteneC=C-C-C-C-C-C-C- CH2CH(CH2)5CH3C8H16

  13. Ball and Stick Form Ways to Show Organics Structural Formula Line Bond Form Space Filling Model Skeletal Form

  14. Alkenes • Also a homologous series General Formula CnH2n • Unsaturated hydrocarbons – have C-C multiple bonds which can be broken to add more atoms to the molecule H HHH • Ex: C=C + H2 H-C -C-H H HHH

  15. Alkynes • Alkynes – hydrocarbons containing a C = C triple bond – sphybtidization • Ethyne -C=C- CHCH C2H2 (acetylene) • Propyne -C=C-C- CHCCH3 C3H4 • Butyne-C=C-C-C- CHCCH2CH3 C4H6 • Heptyne-C=C-C-C-C-C-C- CHC(CH2)4CH3 C7H12 • General Formula = CnH2n-2

  16. Alkadienes • Alkadienes – hydrocarbons containing two C=C double bonds • Butadiene -C=C-C=C- CH2(CH)2CH2 C4H6 • Pentadiene-C=C-C=C-C-CH2(CH)3CH3 C5H8 • Heptadiene-C=C-C=C-C-C-C- CH2(CH)3(CH2)2CH3 C7H12 • General Formula = CnH2n-2

  17. Alkadienes • 3 placements for the two double bonds • Conjugated double bonds (most common) – two double bonds separated by one singe bond • Isolated double bonds – two double bonds separated by more than one single bond • Allenes – hydrocarbons that have two consecutive double bonds

  18. The first 4 Series of hydrocarbons are Aliphatic Hydrocarbons • Aliphatic hydrocarbons – hydrocarbon where carbon atoms bond together in open chains

  19. Arenes • Aromatic Hydrocarbons – hydrocarbons containing rings of 6 carbon atoms joined by alternating single and double bonds • Simplest aromatic hydrocarbon = benzene

  20. Arenes • All bonds are actually identical (C-C and C=C “mixed”) • Can also be shown as

  21. Arenes • We use • The e-‘s are actually shared by all 6 carbons and move freely around the ring (delocalized) • This makes benzene behave like saturated hydrocarbons

  22. Resonance • Compounds like these are resonance hybrids (compounds that can be represented by more than one Lewis structure) • General Formula = CnH1/2n+3

  23. Resonance examples

  24. IUPAC Naming Rules • Name the longest chain (the parent chain) first. • Label the chain to give the lowest numbers to groups or bonds. Priority  C=C then C=C You give the number for the carbon where the multiple bond begins. (Separate numbers and words with a hyphen, and numbers and numbers with a comma). • 6 5 4 3 2 1 • C-C-C-C=C-C 2 –hexene • C-C-C=C-C-C-C 3 – heptyne

  25. IUPAC Naming Rules 3. Give the numbers for any attached groups for the carbons they are attached to, a number for each attached group. Use the number with the groups name. [in front of “main” chain] • If more than one of any group = di-, tri-, tetra-, penta-, hexa-, etc. • Group Names: • F = fluoroI = iodo • Cl = chloroOH = hydroxo • Br = bromoNO2 = nitro

  26. IUPAC Naming Rules c. If there is more than one group attached, the names are listed in alphabetical order (ignore prefixes) in front of the “main” chain d. If the numbers for the side groups are the same from either side of the chain, # from the side that gives the lowest # to the first group in the alpha order.

  27. Summary • Hydrocarbons (straight chains) • Locate and name attached groups • Locate multiple bonds (priority for numbering) • Name base/parent chain

  28. IUPAC Naming Rules 4. Branched chains • Longest continuous chain containing any multiple bonds (if present) • # to give multiple bonds lowest numbers (priority) • Name side groups (alphabetical order)

  29. IUPAC Naming Rules 1-chloro-3,5 - dimethylbezene 5. Benzene • Number starting with a C bonded to an attached group and then continue around the ring • Use the lowest set of #’s possible

  30. IUPAC Naming Rules • 1,3 – dibromo – 2 – fluorobenzene

  31. IUPAC Naming Rules c. If there are just two of the same group attached, we can use the following terms to simplify the bonding positions • Ortho = 1, 2 bonding position • Meta = 1, 3 bonding position • Para = 1, 4 bonding position

  32. O,M, P

  33. Isomer Practice • Isomers – compounds having the same molecular formula but having different structures • Example: C5H11Cl • Draw all isomers by moving Cl (we are only going to use straight chains for C’s)

  34. Isomer Practice Cl • C – C – C – C – C Cl • C –C – C – C – C Cl • C – C – C – C – C

  35. Isomer Practice C4H8Cl2

  36. Isomer Practice • Try C4H8ClI, C4H7I3, C5H10FBr, and C4H7F2Br

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