Download ORGANIC CHEMISTRY BASICS

ORGANIC CHEMISTRY BASICS
OVERVIEW
o ORGANIC CHEMISTRY Used to be considered chemistry of living things (or things that
were once living… like petroleum)
o Since it has been demonstrated that organic compounds can be synthesized in
laboratories we now just say that Organic chemistry is the Chemistry of Carbon
compounds
o Examples: petroleum, medicines, plastics, plants and animals…... (including
YOU!!)
o More than 90% of all known compounds contain Carbon (although it accounts for only
0.2% of the earth’s crust composition)
o Over 6,000,000 organic compounds have been identified – and that number is increasing
daily with the synthesis of new compounds in labs
H
H
O
H
C
C
C
H
H
H
H
H
H
H
C
C
C
H
O
H
H
C
C
H
H
H
O
H
H
C
C
C
C
C
C
H
H
H
BENZENE
CH3
O2N
H
NO2
H
2 - PROPANOL
NO2
2,4,6 - TRINITROTOULENE
O
H2N
H
ETHANOL
ACETONE
H
H
C
CH2CH2N(CH2CH3)2
PROCAINE
H
H
H
H
H
C
C
C
C
H
H
H
H
BUTANE
H
WHAT IS THE DEAL WITH PETROLEUM AND HOW DOES IT FIT INTO THE
ORGANIC CHEMISTY SCHEME?
o PETROLEUM … BLACK GOLD … TEXAS TEA
o Petroleum is a NON-RENEWABLE organic resource
o Consists of a mixture of HYDROCARBONS of many different carbon
chain lengths
o HYDROCARBONS : simplest organic compounds containing only C and H
atoms with “Carbon backbones” that are inherent to organic compounds
H
H
H
H
C
C
C
H
H
H
H
H
H
H
H
C
C
C
C
H
H
H
H
H
BUTANE
PROPANE
H
H
H
C
H
H
METHANE
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
OCTANE
HOW DO YOU KNOW HOW C’s and H’s WILL GET TOGETHER TO FORM
HYDROCARBONS?
o The Octet Rule says that everybody (except H and He) wants to have 8 outer shell
electrons, Carbon has only 4 (it’s glass is both half empty and half full) – so instead of
giving or taking electrons (Ionic bonding) it SHARES electrons – A.K.A COVALENT
BONDING forms MOLECULAR COMPOUNDS – (ORGANIC STUFF!)
o We write LEWIS DOT STRUCTURES to show the sharing of electrons, and thus
formation of bonds between atoms in Covalent compounds
o First get the number of outer shell electrons from the Group # on
Periodic table
o Arrange electrons (dots) so that there is ONE dot on each of 4 sides of
elements symbol, only double them up as pairs when you have more than 4
o On the sides of the symbol where there is only 1 electron you will need to
create a bond with another element to have a shared pair of electrons
o When Carbon shares electrons to fulfill it’s outer shell – it needs to share with other
atoms to get 4 more electrons – so it needs to make 4 bonds
o Carbon needs to make 4 bonds
o Oxygen needs to make 2 bonds
o Hydrogen needs to make 1 bond
o Nitrogen needs to make 3 bonds
o Example of Lewis Dot structure for C and for H
H
C
o A shared pair of electrons between 2 atoms is a BOND, and the 2 dots representing the
bond can be replaced by a line connecting the atoms – this is called a STRUCTURAL
FORMULA
H
H
C
H
H
H
C
H
H
H
o Can also write MOLECULAR FORMULAS that do not show the individual bonds
o Expanded Molecular Formula still shows how atoms are arranged:
 2, propanol = CH3CH(OH)CH3
o Condensed Molecular Formula just shows the number of each atom:
 2, propanol = C3H8O
ASSIGNMENT: PRACTICE WRITING LEWIS DOT STRUCTURES, STRUCTURAL
FORMULAS, AND MOLECULAR FORMULAS
1. Draw Lewis Dot Structures for the following elements:
Oxygen
Silicon
Carbon
Nitrogen
Sulfur
Phosphorus
2. Given the Expanded molecular formulas, first create a 3-D molecular model of the
alkanes below. Then draw the correct STRUCTURAL FORMULAS.
CH3CH2CH3
CH3CH3
CH3OH
CH3CH2CH2CHCH3CH3
3. Use 3-D molecular models to create a reasonable structure from the condensed molecular
formulas below. Draw a STRUCTURAL FORMULA once you are satisfied that your
models are reasonable, taking into account how many bonds each element makes.
C4H10
C6H14
4. Compare the structural formulas you drew for the molecules in Question 3 with another
lab group. Did everyone come up with the same structure? If not, who is correct?
5. Try to arrange the atoms in the molecule C7H14 in different ways, while still keeping all of
the atoms happy. Draw as many DIFFERENT structural formulas as you can below.
CLASSES OF ORGANIC COMPOUNDS
o HYDROCARBONS
o ALKANES – simplest hydrocarbons – just C and H, and all single bonded –
no funny business!!
 Propane =
H
H
H
H
C
C
C
H
H
H
H
o ALKENES – just like alkanes, but they have at least 1 carbon – carbon
DOUBLE BOND
 Propene =
H H H
H C C C H
H
o ALKYNES – you know what they say… “it takes all kines” tee hee – just
like alkanes, but they have at least 1 Carbon – Carbon TRIPLE BOND

Propyne =
H
H C C C H
H
o NAMING HYDROCARBON CHAINS
o Use IUPAC (International Union of Pure and Applied Chemistry) prefixes
to tell number of carbons in longest chain
o Add ending to tell the type of hydrocarbon (ane, ene, or yne)
Number of
Carbon atoms
1
2
3
4
5
6
7
8
9
10
Prefix
Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
Non
Dec
Structural Formulas and Naming of Alkanes and Isomers Lab
Name ____________________
Date_________ Period_______
OBJECTIVE: To be able to assemble models of several simple hydrocarbons and relate the 3-D shapes of
molecules to their names and structural formulas used to represent them on paper.
PART 1 – STRAIGHT CHAIN ALKANES
PROCEDURE:
1. Assemble a 3-D molecular model of methane (CH4) and draw the corresponding structural formula in
Chart 1 on back of paper.
2. Repeat this process by adding one more C atom in place of a H in the methane molecule and adding
enough H atoms to complete the 2 carbon molecule. Repeat this for the compounds with 3 – 10 Carbon
atoms, keeping in mind the number of bonds that C and H need.
3. When you have successfully created and written structures for all of the alkanes listed in the chart, go
back and find the correct prefix for the number of carbons and list them in the chart.
4. Now go back and correctly name each of the alkanes.
5. Finally, provide the condensed molecular formula for each alkane in the space provided in the chart.
PART 2 – BRANCHED CHAIN ALKANES - A.K.A. ISOMERS
1. Assemble a 3-D molecular model with the molecular formula C4H10.
2. Create as many different arrangements of the atoms in C4H10 as you possible can, and draw the
structural formulas below.
3. Check with your teacher to determine if you have the identified the correct number of ISOMERS –
compounds with the same molecular formula, but different structural formulas (ways that the atoms
are put together)
4. Now try to make as many different isomers of hexane (C6H14) as possible and draw the structural
formulas below.
CHART 1
Number
of
Carbon
atoms
1
2
3
4
5
6
7
8
9
10
Prefix
Name of Alkane
Molecular
formula
(condensed)
Structural formula
QUESTIONS
1. What is the trend in the ratio of C to H in the molecular formulas from Chart 1?
2. Write the molecular formula for an alkane containing 25 Carbon atoms.
3. Did you decide to write the condensed or expanded molecular formula for the previous question? Why?
4. As the number of carbons in a chain increases, what seems to happen to the number of ISOMERS that
can be made for the same molecular formula?
5. Would you expect all of the different ISOMERS of a compound like hexane to have the same physical
and chemical properties?
EFFECTS OF CARBON CHAIN LENGTHS
HOW DO WE GET ALL OF THESE DIFFERENT PRODUCTS FROM THAT THICK BLACK
SLUDGE?
o Petroleum removed from the ground as “Crude Oil” is sent to the Refinery for processing
– separating by DISTILLATION into fractions of similar carbon chain lengths
WHAT ARE THE DIFFERENT CARBON CHAIN LENGTH FRACTIONS USED FOR?
ASSIGNMENT: You Decide pg. 173 – Uses of Fractions
HOW IS THE LENGTH OF THE CARBON BACKBONE CHAIN RELATED TO BOILING
POINT?
o INTERMOLECULAR FORCES are attractions between molecules of a particular
substance (how much molecules of methane “like” each other for example)
o Can be determined by the normal physical state of the substance (solid,
liquid, gas)
Number
of
Carbon
atoms
1
2
3
4
5
6
7
8
9
10
Prefix
Molecular
formula
Name of
Alkane
Melting
Point
(C)
Boiling
Point
(C)
Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
Non
Dec
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
methane
ethane
propane
butane
pentane
hexane
heptane
octane
nonane
decane
-182
-172
-187.7
-138.4
-129.7
-95
-90.6
-56.8
-51
-29.7
-161
-88
-42.1
-0.5
36.1
69
98.4
125.7
150.8
174.1
ASSIGNMENT: Your Turn pg. 132 – Alkane Boiling Point Trends
ASSIGNMENT: Your Turn pg. 184 – Alkane Boiling Points: Isomers