1 ch. 10: alkanes chem 20 el camino college. 2 organic chemistry more than 90% of compounds are...
TRANSCRIPT
2
Organic Chemistry
More than 90% of compounds are organic compounds.
For pronunciation of organic compound names go to
www.merriam-webster.com/dictionary
www.howjsay.com
3
Organic Chemistry
Organic chemistry covers compounds made of carbon and hydrogen
Other elements, such as O, N, S and Cl may be present
4
Organic Chemistry
Organic compoundsThey are mostly covalently bonded
moleculesUsually low melting pointsUsually low boiling pointsThey are usually not soluble in water,
unless a polar group is present
5
Organic Chemistry
Inorganic compoundsThey are mostly ionic compounds, some are
covalentUsually high melting pointsUsually high boiling pointsThey are usually soluble in water.
6
ALKANES
Remember that carbon has 4 bonds and is often tetrahedral.
Wedge formula: Solid wedge represents bond coming forward. Broken wedge represents bond going to the back. Ordinary line represents bond on the plane
7
Lewis Structures
Each bonding pair is represented by a dash. Sometimes we draw long molecules with straight lines, but actually they are not flat
C O C H
H
H
H
H
H
::
8
Alkanes
Alkanes are a class of hydrocarbons in which the atoms are connected only by single bonds.
The general formula for open-chain alkanes is Cn H2n+2 .
9
Alkanes CH4 methane (1C)
CH3CH3 ethane (2C)
CH3CH2CH3 propane (3C)
CH3CH2CH2CH3 butane (4C)
CH3CH2CH2CH2CH3 pentane (5C)
CH3CH2CH2CH2CH2CH3 hexane (6C)
CH3CH2CH2CH2CH2CH2CH3 heptane (7C)
CH3CH2CH2CH2CH2CH2CH2CH3 octane (8C)
CH3CH2CH2CH2CH2CH2CH2CH2CH3 nonane (9C)
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 decane (10C)
10
Drawing Formulas
In expanded formulas, every bond is shown In condensed formulas, carbons are shown with
the correct number of hydrogen atoms, but not every bond is shown
In alkane, C will always have 4 bonds, H will always have 1 bond
12
Drawing Formulas Hexane has six carbons. Draw expanded
and condensed formulas for hexane. (Note: make sure every carbon has 4 bonds)
C C
H
H
H
H
C
H
C C C H
H
H
H
H
H
H
H
H
H3C CH2 CH2 CH2 CH2 CH3
13
Drawing Formulas Note--the chains in formulas may not be
shown as a straight line. Ex. What compounds are these?
H3C CH2 CH2
H2C CH2
CH2H3C
H3C CH2
CH2H3C
butane heptane
14
Skeletal (Geometric)Formula(Stick structure)
Skeletal formulas contain zigzag lines Every corner and every end represents a carbon H atoms are filled in mentally Butane:
Hexane
15
Structural Isomers Isomers have the same chemical formula, but
atoms are attached differently 2 different isomers have different properties Are these isomers, or the same molecule?
or
or
isomers
same molecule
16
Stereoisomers In stereoismers atoms are attached to each other in the same
way But they are different in the way atoms are oriented in space Chiral center is a carbon atom to which 4 different groups are
attached.
17
Fisher projection A cross represents a chiral center. Vertical lines represent bonds going away to the back Horizontal lines represent bond coming forward
18
Cycloalkanes Cycloalkanes have the carbons connected in a “ring” Use cyclo in the name Ex. Condensed formula
for cyclohexane
Draw a geometric formula for cyclopropane.What is the chemical formula?
H2C
H2C
CH2
CH2
CH2
CH2
C3H6
19
Substituents Alkanes can have attachments Common attachment names:
• CH3- methyl
• CH3CH2- ethyl
• CH3CH2CH2- propyl
• F-, Cl-, Br-, I-fluoro, chloro, bromo, iodo
• isopropyl
HC
H3C
H3C
20
Alkanes with Substituents 1. Write the name of the longest continuous
carbon chain H3C CH2 CH2
HC CH3
CH3
The longest chain has 5 carbons: pentane
H3C CH2 CH2
HC CH3
CH3
21
Alkanes with Substituents 2. Number the carbon chain from the end
nearer a substituent
3. Give the location and name of the substituent. Use a hyphen after the number
H3C CH2 CH2
HC CH3
CH31
2
345
2-methylpentane
23
Alkanes with Substituents
Name these
C C
H
H
H
H
C
H
C C C H
H
H
H
H
CH2
H
H
H
H3C
Br
2-bromopropane 3-methylheptane
24
Alkanes with Substituents Name these, write the formula
1-bromohexaneC6H13Br
4-ethylnonaneC11H24
Br
3-methylnonaneC10H22
25
Alkanes with Substituents Draw the skeletal formula
Draw the expanded formula
Br
2-bromobutane
1-iodopropane
1-chlorodecane
cyclobutane
Cl
H C C C H
I
H H
H H
H
C
C C
C
H
H
H
H
H
H
H
H
26
Alkanes with Substituents Name these, write the formula
cyclopentaneC5H10
2-fluorohexaneC6H13F
4-propylheptaneC10H22
F
27
Alkanes with Substituents 4. Name substituents in alphabetical order
Name this2-bromo-1-iodohexane
C C
H
H
H
H
C
H
C C C H
H
H
H
H
H
Br
H
I
CH3
Br 3-bromo-2-methylpentane
28
Alkanes with Substituents Name these
1-bromo-2-chlorobutane
2-chloro-1-fluorobutane
Cl
Br
Cl
F
F
Br
1-bromo-1-fluoro-2-methylpropane
5. Use prefixes like di-, tri-, tetra- for more than one copy of a substituent Every substituent must have its own number Prefixes are not part of alphabetical order.
30
2,3-dimethylbutane
2,2-dibromobutane
C C
H
H
H
CH3
C
H
C
H
CH3
H
H
H
Br Br Cl Cl
Cl
1,2,2-trichlorobutane
32
C C
H
Br
H
Br
C
H
C
H
CH3
H
H
H
C C
H
Br
H
Br
CH
H H
CH3
F
Br
3-bromo-2-fluoropentane
1,2-dibromo-3-methylbutane
1,2-dibromobutane
33
7. When a single substituent is attached to a cycloalkane, no number is needed.
ethylcyclobutane
Cl
chlorocyclohexane
Write the name and chemical formula:
C6H12
34
Draw these ethane 2-methylpropane
bromocyclopentane
1,4-dichloro-2-methylbutane
1,1,2,3-tetrabromopropane
Br
Cl
ClCH3
Br
Br
Br
Br
H3C CH3
35
Properties, Uses Alkanes are nonpolar, so they’re insoluble in water Alkanes are less dense than water (they float on
water) Common alkanes: methane (natural gas), propane
(bbq fuel), butane (lighter fuel), octane (fuel) Alkane mixtures also form gasoline, mineral oil,
and vaseline.
36
Combustion The burning of methane in a Bunsen burner is
an example of combustion of an alkane alkane + O2 CO2 + H2O + energy Write a balanced equation for the combustion
of methane gas
_____(g) + O2(g) CO2(g) + H2O(g)CH4 22
37
Compound TypesAlkenes (contain C=C)Alkynes (contain CC)Alcohols (contain -OH)Ethers (contain C-O-C)Aldehydes (contain H-C=O)Ketones (contain C=O)Carboxylic acids (contain HO-C=O)Esters (contain RO-C=O)Amines (contain N).
47
What is the compoud type?
H3C
C
CH3
O
H3C OCH3
O
H3C
C
OH
O
H3C
C
H
O
alkene
ketone
amine
ester
carboxylic acid
aldehyde
alkaneH3C
NH
CH3
48
Substitution Reactions Your next organic reactions will be on
haloalkanes (alkanes with a halogen atom substituent)
In substitution reactions, one halogen will be substituted for another halogen
CH3Br + Cl- CH3Cl + Br-
50
Draw Products, Name the Organic Product
2-chloro-2-methylpropane
CH3
C I
CH3
H3C + Cl- + I -
CH3
C Cl
CH3
H3C
51
Name These
bromoethane
Br Br
Br
Br BrBr BrBr
Br
bromoethane
1,1-dibromoethane
1,2-dibromoethane
1,1,2-tribromoethane
52
Name These
2-bromopropane
2-bromo-2-methylpropane
1,2-dibromo-2-methylpropane
1,1,1,2-tetrabromo-2-methylpropane
Br
Br Br
Br Br Br
Br
Br