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Unit 2Introduction 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
3. Organic compounds decompose on heating easier than inorganics
4. Organic reactions are much slower (min, hours, days) than inorganic reactions (seconds)
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
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
Isomer Example
C5H12
C C
-C-C-C-C-C- -C-C-C-C- -C-C-C-
C
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
How Carbon Bonds
Carbon’s 4 covalent bonds form a tetrahedron (109.5° bond angle)
Hydrocarbons!
Hydrocarbons – compounds containing only hydrogen and carbon
Alkanes – hydrocarbons that have all C-C single bonds
Naming# of C
Name Structural Formula
Condensed Formula
Molecular Formula
1 Methane -C- CH4 CH4
2 Ethane -C-C- CH3CH3 C2H6
3 Propane -C-C-C- CH3CH2 CH3 C3H8
4 Butane -C-C-C-C- CH3(CH2)2 CH3 C4H10
5 Pentane -C-C-C-C-C- CH3(CH2)3 CH3 C5H12
6 Hexane -C-C-C-C-C-C- CH3(CH2)4 CH3 C6H14
7 Heptane -C-C-C-C-C-C-C- CH3(CH2)5 CH3 C7H16
8 Octane -C-C-C-C-C-C-C-C-
CH3(CH2)6 CH3 C8H18
9 Nonane -C-C-C-C-C-C-C-C-C-
CH3(CH2)7 CH3 C9H20
10 Decane -C-C-C-C-C-C-C-C-C-C-
CH3(CH2)8 CH3 C10H22
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
Naming
Alkanes are Saturated Hydrocarbons – hydrocarbons where each C has 4 single covalent bonds (no more atoms can be added)
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-C CH2CHCH3
C3H6
Butene C=C-C-C CH2CHCH2CH3
C4H8
Octene C=C-C-C-C-C-C-C- CH2CH(CH2)5CH3
C8H16
Ways to Show Organics
Line Bond Form
Ball and Stick Form
Space Filling Model
Skeletal Form
Structural Formula
AlkenesAlso 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 H H H
Ex: C=C + H2 H-C -C-H
H H H H
Alkynes Alkynes – hydrocarbons containing a C = C
triple bond – sp hybtidization
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
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
Alkadienes3 placements for the two double bondsConjugated 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
The first 4 Series of hydrocarbons are Aliphatic HydrocarbonsAliphatic hydrocarbons –
hydrocarbon where carbon atoms bond together in open chains
Arenes Aromatic Hydrocarbons – hydrocarbons
containing rings of 6 carbon atoms joined by alternating single and double bonds
Simplest aromatic hydrocarbon = benzene
Arenes
All bonds are actually identical (C-C and C=C “mixed”)
Can also be shown as
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
Resonance
Compounds like these are resonance hybrids (compounds that can be represented by more than one Lewis structure)
General Formula = CnH1/2n+3
Resonance examples
IUPAC Naming Rules1. Name the longest chain (the parent chain) first.
2. 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
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]
a) If more than one of any group = di-, tri-, tetra-, penta-, hexa-, etc.
b) Group Names: F = fluoro I = iodo
Cl = chloro OH = hydroxo
Br = bromo NO2 = nitro
IUPAC Naming Rulesc. 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.
Summary
Hydrocarbons (straight chains)Locate and name attached groupsLocate multiple bonds (priority for
numbering)Name base/parent chain
IUPAC Naming Rules
4. Branched chainsLongest continuous chain containing
any multiple bonds (if present)
# to give multiple bonds lowest numbers (priority)
Name side groups (alphabetical order)
IUPAC Naming Rules
1-chloro-3,5 - dimethylbezene
5. BenzeneNumber starting with a C bonded to an
attached group and then continue around the ring
Use the lowest set of #’s possible
IUPAC Naming Rules
1,3 – dibromo – 2 – fluorobenzene
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 positionMeta = 1, 3 bonding positionPara = 1, 4 bonding position
O,M, P
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)
Isomer Practice
Cl
C – C – C – C – C
Cl
C –C – C – C – C
Cl
C – C – C – C – C
Isomer Practice
C4H8Cl2
Isomer Practice
Try C4H8ClI, C4H7I3, C5H10FBr, and C4H7F2Br