1) Isomers 2) Naming with Substituents 3) Naming Cycloalkanes 4) Properties of Alkanes 5) Combustion of Alkanes 6) Functional Groups
Dec 22, 2015
1) Isomers2) Naming with Substituents
3) Naming Cycloalkanes4) Properties of Alkanes
5) Combustion of Alkanes6) Functional Groups
Recall the basics of naming….
Root Names:
1 meth 2 eth 3 prop 4 but 5 pent6 hex 7 hept 8 oct 9 non 10
dec
Prefix (attached groups)Root (number of carbons in the main chain)Suffix (functional group)
Substituents…Alkanes with four or more carbons can have side groups called branches or substituents, which are attached to the carbon chain.that replace at least one H on the alkane chain.
When two compounds have the same molecular formula, but differ in the order in which the atoms are bonded, they are called structural isomers.
Chapter 11, Section 4© 2013 Pearson Education, Inc. 4
Structural Isomers of C4H10
Isomershave the same
molecular formula.have different
structural arrangements.
of C4H10 consist of a straight chain and a branched chain, each with 4 carbon atoms.
branch or substituent
4
Chapter 11, Section 4© 2013 Pearson Education, Inc. 5
Isomers of Pentane (C5H12)
Isomers of pentanehave the same molecular formula.have different structural arrangements.consist of a straight chain and two
branched chains.
5
Chapter 11, Section 4© 2013 Pearson Education, Inc. 6
Isomers of Alkanes
The number of structural isomers of alkanes increases rapidly as the number of carbon atoms increases.
Insert table of structuralisomers middle pg 420
6
Chapter 11, Section 4© 2013 Pearson Education, Inc. 7
Learning Check
Identify each pair of condensed structural formulas as structural isomers or the same molecule.
CH3 CH2 CH2 CH3CH3 CH CH3
CH3
CH3 CH2 CH2 CH2CH2 CH2 CH3
CH3CH2H3C
7
A.
B.
C.
Chapter 11, Section 4© 2013 Pearson Education, Inc. 8
Solution
Identify each pair of condensed structural formulas as structural isomers or the same molecule.
8
A.
B.
C.
structural isomers
structural isomers
same molecule
CH3 CH2 CH2 CH3CH3 CH CH3
CH3
CH3 CH2 CH2 CH2CH2 CH2 CH3
CH3CH2H3C
Each isomer of a given molecular formula will have its own unique structure and name. Let’s look at how to name compounds that have attachments….
First…what are some of the commonAttachments?....(next slide).
Common AttachmentsCH3
CH2CH3
Methyl
Ethyl
CH2CH2CH3
CH
CH3
CH3
Propyl
Isopropyl
F = f luoro Cl = chloro Br = bromo I = iodo
What is the base name of this compound?…What is the name Of the attachment? One final thing is needed. A number! What would the number be for this attachment?
Attachment “Rules”1) Select the longest chain of carbons first, then
go back and determine what the attachments are.
2) Name the attachment(s). The name of the attachments is in the prefix part of the name of the compound (in front).
3) The attachment needs a number so you know where it is attached on the chain of carbons.
4) Number so that the attachment gets the smallest possible number.
Your book’s way of naming Alkanes with Substituents
14
What would this name be?
Number so that
Let’s try to name this compound…
What would this name be?
Typical alkyl
4-ethyl octane
Try to draw 4-isopropyl decane….
A few ways to draw 4-isopropyl decane….
If you have groups that are the same, there are prefixes thatcan be used … so let’s work on this name…
Typical alkyl
With two different groups, you put theattachments alphabetically
Br
4-bromo-6-ethyl nonane
Br
Naming Cycloalkanes with attachments…1 attachment, just add it to the front of the
name.
Cl
So this name is…Chloro cyclobutane
Cl
Naming Cycloalkanes with 2 (or more) attachments…
Alphabatize the attachments &Give the smallest possible numbers.
Br
So this name is…
1-bromo-3-methyl cyclopentane
Br
Try to draw 1,4-dichloro cyclohexane…
Ways to draw 1,4-dichloro cyclohexane…
Cl
Cl
Cl
Cl
Note the use of “di” since the attachments were the same.
Two groups…With two groups, you can have stereoisomers
Cis = both groups are on the same side (top or bottom)
Trans = groups are on opposite sides
Cl
Cl
H
H
H
H
Cl
Cl
H
Cl
Cl
H
Cis Trans
Naming with two groups…Let’s try naming a few compounds together….(There are some hints on the following slides)…
ClH
H
H
F
CH3
HBr
HH
Naming with two groups…Is this cis or trans ? (remember, that is in the prefixPart of the name when there are two groups)….
ClH
H
This one is cis since the ethyl group and chlorineare both on the top of the ring (or on the bold lines)
What is the whole name?
ClH
H
ethyl group
chlorine
Cis 1-chloro – 4 – ethyl cyclohexane
ClH
H
What is the stereochemistry of this ring?(Then we will work on the rest of the name!)
a) Cisb) trans
HBr
H
This is trans because the bromine and the isopropylgroups are on opposite sides of the ring. The bromineis on a dashed line (meaning it’s on the back) and the isopropy is on a bold line (meaning it’s on the front)…
What is the rest of the name?
HBr
H
bromine (back)
isopropyl (front)
The full name is…
Trans 1-bromo-2-isopropyl cyclobutane
HBr
H
Last one together…Is this a) cis or b) trans?....
H
H
F
CH3
Cis…It is cis since both of the groups are on the
“back” of the structure (on the dashed lines)…
H
H
F
CH3
f luorine (on the back)
methyl (on the back)
This is…
H
H
F
CH3
Cis-1-fluoro-2-methylcyclopentane
You try one in your composition books (I will walk around & check)…
Draw trans-1,3-difloro cyclohexane
Should look something like this…
Draw trans-1,3-difloro cyclohexane
H
F
F
H
Chapter 11, Section 4© 2013 Pearson Education, Inc. 42
Alkanes: Physical StatesAlkanes are…gases when they
have only 1 to 4 carbon atoms.
liquids when they have 5 to 8 carbon atoms.
solids when they have 9 or more carbon atoms.
Chapter 11, Section 4© 2013 Pearson Education, Inc. 43
Alkanes: Solubility and Density
Alkanes arenonpolar.insoluble in water.less dense than
water (1.0 g/mL) with a density from (0.62 g/mL to 0.79 g/mL). Vegetable oil, an organic
compound, is not soluble in water.
Chapter 11, Section 4© 2013 Pearson Education, Inc. 44
Alkanes in OilIf there is an oil spill,alkanes in the oil do
not mix with the water,
alkanes form a thin layer on the surface of the water spreading large distances,
cleanup includes mechanical, chemical, and microbiological methods
In oil spills, large quantities of oil spread over the surface of the water.
Chapter 11, Section 4© 2013 Pearson Education, Inc. 45
Alkanes: Melting and Boiling Points
Alkaneshave the lowest melting and boiling
points of all organic compounds.have only nonpolar bonds, C—C and C—
H.have weak dispersion forces which
increase when more carbons are present.
Chapter 11, Section 4© 2013 Pearson Education, Inc. 46
Branched Alkanes: Melting and Boiling Points
The boiling and melting points of branched alkanes are lower than their straight-chain isomers because they are more compact.
There is more contact betweenhexane molecules (red and blacklicorice) than between the surfaces of 2,3-dimethylbutane molecules (tennis balls).
Analogy…
Neatly stacked, fit well vs. Random packing
Cycloalkanes: Melting and Boiling Points
Cycloalkanes have higher boiling points
than straight-chain alkanes with the same number of carbon atoms.
restricted rotation around C—C bonds, maintaining rigid structures.
Learning Check
For the following pairs of hydrocarbons, which one has the higher boiling point? Why?
1. Butane or octane
2. Hexane or 2,3-dimethylbutane
Solution
For the following pairs of hydrocarbons, which one has the higher boiling point? Why?
1. Butane or octane Octane (has more carbon atoms) and,
therefore, a higher boiling point.
2. Hexane or 2,3-dimethylbutane Both alkanes have the same number of carbon atoms. Hexane is not branched and, therefore, has the higher boiling point.
Combustion of Alkanes
Alkanes… contain single C—C bonds which are difficult to
break.are the least reactive group of organic compounds.burn readily in the presence of oxygen. undergo combustion to produce carbon dioxide,
water, and energy.
Combustion of Alkanes
We use methane gas to cook food and heat homes.
Propane gas is used in portable heaters and gas barbecues.
Our cells get energy from the combustion of glucose.
Balancing a Combustion Equation…
Write the equation:
Balance C:
Balance H:
Balance O with O2:
Recommended Order…
Crude Oil
Hydrocarbons in crude oil are separated by their different boiling points in a process called fractional distillation which removes groups of hydrocarbons by continually heating the mixture to higher temperatures.
Crude Oil
Chapter 11, Section 4© 2013 Pearson Education, Inc. 57
Learning CheckPropane gas is used to provide heat for cooking. Write a balanced equation for the combustion ofpropane.
Step 1: What is the equation?
Unbalanced equation:
Propane has 3 carbons and therefore 2n+2 hydrogens, or 8 hydrogens(or you can draw it out & count the # of hydrogens)
Step 2: Balance the carbons…
Unbalanced equation:
Balance C:
Step Three: Balance the Hydrogens
Unbalanced equation:
Balance C:
Balance H:
Step 4: Balance the oxygens…
Unbalanced equation:
Balance C:
Balance H:
Balance O:
Write a balanced equation for the reaction for the complete combustion of heptane, C7H16.
Learning Check (You can work this one at home)…
Write a balanced equation for the reaction for the complete combustion of heptane, C7H16.
Balanced equation:
Solution
Chapter 11, Section 4© 2013 Pearson Education, Inc. 64
Elements in Organic Compounds
In organic molecules, carbon atoms can form bonds with atoms of O, S, N, P, or halogens,F, Cl, Br and I.
64
Functional groups…are a characteristic feature of organic
molecules that behave in a predictable way. are composed of an atom or a group of
atoms.are groups that replace a H in the
corresponding alkane.provide a way to classify families of organic
compounds.
Functional Groups
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Chapter 11, Section 5© 2013 Pearson Education, Inc.
Alkenes and Alkynes
Alkenes contain a double bond between adjacent carbon atoms.
Alkynes contain a triple bond.
Aromatic compounds contain a benzene ring.
C C
C C
66
Alcohols, Thiols, and Ethers
An alcohol contains the hydroxyl (–OH) functional group.
Thiols contain a thiol (–SH) functional group.
In an ether, an oxygen atom is bonded to two carbon atoms (–C–O–C–).
H3C CH2 OH
H3C CH2 SH
H3C O CH3
Thiol
67
Aldehydes and Ketones
An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom, attached to at least one hydrogen atom.
In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms.
C
O
H3C H
C
O
H3C CH3
68
Carboxylic Acids and Esters
Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group.
An ester has a
carbon attached to the oxygen (not a hydrogen).
C
O
H3C OH
C
O
H3C OCH3
69
Chapter 11, Section 4© 2013 Pearson Education, Inc. 70
Amines and Amides
In an amine, the functional group is a nitrogen atom.
In an amide, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group.
NH3C
H
H NH3C
CH3
H NH3C
CH3
CH3
H3C C
O
NH2
70
Learning Check
Classify each of the following as alcohol, ether, aldehyde, ketone, carboxylic acid, ester, or amine.
A.
B.
C.
D.
E.
CH2 CH2 CH3HO
O CH2 CH3H3C
H3C CH2 NH2
H3C C
O
OH
H3C C
O
O CH3
71
Learning Check
Classify each of the following as alcohol, ether, aldehyde, ketone, carboxylic acid, ester, or amine.
A.
B.
C.
D.
E.
CH2 CH2 CH3HO
O CH2 CH3H3C
H3C CH2 NH2
H3C C
O
OH
H3C C
O
O CH3
72
alcohol
ether
amine
carboxylic acid
ester