Transcript CHAPTER 11 BONDING AND MOLECULAR STRUCTURE:
CHAPTER 11
BONDING AND MOLECULAR STRUCTURE:
ORGANIC CHEMISTRY
All bold numbered problems .
Overview
• • •
Organic chemistry is the study of compounds containing carbon combined with other non-metals. Bonding plays a critical role in understanding the reactivity of these compounds. These compounds are referred to as hydrocarbons since they are primarily hydrogen and carbon.
Overview
Overview
•
Carbon uses sp 3 , sp 2 , and sp hybridization in forming the four bonds per carbon atom common to almost all carbon compounds.
• •
With sp hybridization, there are two (2)
p
bonds and 2
s
bonds.
With sp
p
2 hybridization there is one (1) bond and 3
s
bonds.
Why Carbon
sp3, sp2, and sp hybridization
Allotropes of Carbon Carbon only (no other atom) compounds
FUNCTIONAL GROUPS 1. Alkane 2. Alkene 3. Alkyne 4. Alkyl halide 5. Aromatic 6. Alcohol 7. Aldehyde 8. Ketone Organic chemistry is the study of compounds containing carbon.
The goal of studying Organic chemistry is the making of carbon-carbon bonds, C-X, C-O, C-N, and C-S bonds to make new molecules 9. Carboxylic Acid 10. Ester 11. Amine 12. Amide
Inorganic molecules like CO, and CO 3 -2 are not considered organic molecules.
1. Alkanes
Figure 11.4
10
Name methane ethane propane butane pentane hexane heptane octane nonane decane # of C's 1 2 3 4 5 6 7 8 9 10 Structural Formula CH 4 CH 3 CH 3 CH 3 CH 2 CH 3 CH 3 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 BP (C
) -161 -88 -45 -.5
36 69 98 125 151 175 MP (C
) -183 -172 -187 -138 -130 -95 -90 -57 -54 -30
Alkanes
12
Abbreviated, common method to write organic cmpds Name methane ethane propane butane pentane C Structural Formula CH 4 CH 3 CH 3 CH 3 CH 2 CH 3 CH 3 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 3
ALKANES
• There are frequently many hydrocarbons with the same formula. These are called structural isomers.
C 5 H 12 has three isomers C 10 H 22 has 75 isomers C 20 H 42 has 366,319 isomers
Isomers of Butane-5 Carbon chains
C
6
H
14
has five isomers, draw them.
Cycloalkanes
• •
Cycloalkanes are ring structures and have the general formula C n H 2n . Do not confuse these compounds with the alkenes which have the same general formula.
2. ALKENE AND 3. ALKYNE
• •
These compounds are referred to as unsaturated. Alkenes contain one or more double bonds and alkynes contain one or more triple bonds.
Saturated –vs- Unsaturated
Saturated Hydrocarbon C 15 H 32
Unsaturated Hydrocarbon Contains either double and/or triple bonds Notice how the chains do not line up
ALKENES
ALKYNE
Physical properties change
Isomers have different physical as well as different chemical properties
•
Nomenclature
• Organic Functional Groups and Nomenclature
Substituents - saturated carbon substituents are called alkyl groups and are named based on the naming of the normal alkanes.
meth
y
l e t hyl H H C H H H H C H H C
H
H CH3 CH 2 CH 3 Me Et
Nomenclature Haloalkane
Alcohol 26
Ether 27
Amine 28
Aldehyde 29
Ketone 30
Carboxylic acid 31
Ester 32
Amide 33
Common Alcohol Names
What is the name of this Alcohol?
methyl Methanol alcohol
C 1
The main chain is numbered such that the first substituent encountered along the chain receives the lowest possible number.
C H 3 C 2 C 3
2-me
thylpentane C 4 C 5 CH 3 NOT C 5 C
4
C 3 4
-
methylpentane C 2 C 1
If two or more identical substituents are attached to the same C-chain , prefixes di-, tri-, tetra-, etc. are used with numbers to indicate position.
C 1
C
H 3 CH 3 C 2 C 3 C 4 2 ,4
-
dimethylpentane C
5
C 1 CH 3 C
2
C 3 C 4 CH 3 2,2
-
dimethylpentane C 5
If two different substituents are attached to the carbon chain, name them in alphabetical order.
C 1 C H 2 CH 3 C H 3 C 2 C 3 C 4 2
-
ethyl
-4-
methylpentane C 5 CH 3 Numbering starts at the side with the heavier functional Group CH 2 CH 3 C 1 C 2 C 3 C 4 Numbering starts closest to 1 st functional group 4
-
ethyl
-
2
-
methylhe
x
ane C 5 C 6
C C C C 3 C C 2 C
C
Practice
C C C C 4 C 1 C 5 C 6 3-ethylhexane C
Practice methylcyclopentane 1-ethyl-2-methylcyclopentane
C Practice Br Cl
C
C C
2-bromo-4-chl oropropane
C
C Br
C Br C Br
C 2,2,4-tribromopropane
C
Draw the following
• • • • • •
Butane Butene Butyne Butanol Butanal Butanone
• • • • • •
Dibutyl ether Butanoic acid Butyl butanoate Butyl amine Dibutyl amine Tributyl amine
Structure, Bonding, and Isomerism
• Alkenes have the possibility of cis- trans isomerism since the pi bond does not permit rotation. • Illustration: the three isomers of butene (isobutene is actually a propene).
• The position of the atoms changes the physical properties listed. • If a molecule has two double bonds between carbon atoms, it is called a diene.
Double and Triple Bonds
Double and Triple Bonds trans-2-butene
Double and Triple Bonds trans-2-pentene
1. Draw a cis, trans-2,4-heptene 2. Name the following
Preparation of Alkenes and Alkynes
• Acetylene aka ethyne, from calcium carbide, CaC 2 • Steam cracking for the formation of ethylene, ethene, from ethane.
Addition Reactions
• Symmetrical addition is simple, but asymmetrical addition follows Markovnikov's rule: the hydrogen adds to the carbon with the most hydrogen .
For alkynes, the addition is always two mole to one mole of alkyne, the product being a substituted alkane. If hydrogen gas is added, the process is called hydrogenation.
Markovnikov Addition
CH 3 CH 2 CH 2 CH 2 CH 2 C CH HBr ethanol CH 3 CH 2 CH 2 CH 2 CH 2
?
Br C H CH HBr ethanol CH 3 CH 2 CH 2
?
2 CH 2 C Br Br H CH H The hydrogen adds to the carbon with the most hydrogen
ALKENE to ALKANE
ALKENES: Addition
ALKENES: Elimination
AROMATIC COMPOUNDS
Naphthalene Benzene
AROMATIC COMPOUND
• • •
See your text for physical properties of these compounds. Aromatics like benzene have sp 2 hybridization with
delocalized pi electrons
. The
delocalized p
bonding is the key to these compounds. They do not undergo addition reactions like alkenes and alkynes, but rather react by way of
substitution
.
Substitution reactions with aromatic compounds, not addition C n
H
2
n+
2 CH 3 CH 3 + Br 2 C n H 2n CH 2 CH 2 + Br 2
n
o react ion Br Br H C H C H H Br
C
n H n
+
Br 2 + HBr
OH Naming Aromatic Compounds CH 3 CH 3 CH 3 phenol t
o
luene o-xylen
e
napthalene anthracene
X ortho -- o meta -- m para -- p CH 3
CH 3
CH 3 CH 3 o-xylene m-xylene CH 3 CH 3 p-xylene
Benzene Reactions
halogenation
Br + Br 2 + HBr
Benzene Reactions
nitration
+ HNO 3 (conc) H 2 SO 4 (conc) NO 2 + H 3 O +
Benzene Reactions
alkylation
CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 Cl AlCl 3
ALCOHOLS
ALCOHOLS
Naming Alcohols
•
The alkane name is modified by dropping the e and adding
ol.
CH 3 CH 2 OH is ethanol
•
If three OH groups are present, the molecule is called a
triol.
CH 3 C(OH) 3 is ethantriol
Primary, secondary, and tertiary alcohols R H C OH H primary or 1° R R C OH H secondary or 2° R R C OH R tertiary or 3°
What type of alcohol’s are these?
1°, 2°, 3°?
Metalation of Alcohols
Sodium metal reacts with an alcohol to produce hydrogen gas and the sodium alkoxide, refered to as a metalation, since the oxygen is still attached.
CH 3 CH 2 OH + NaH OH + NaOH CH 3 CH 2 O Na + + H 2 O Na + + H 2 O
Chemistry of Alcohols
1. Alcohols can go through substitution, and elimination reactions Which means Alcohols are either oxidized or reduced 67
Formation of ALCOHOLS addition reaction to an alkene H 2 C CH 2 + H 2 O H 3 PO 4 CH 3 CH 2 OH Could also be called an oxidation reaction because we’re adding oxygen to the carbon
•
Substitution An alcohol reacts with HX to produce the
alkylhalide
and water, where X is Cl, Br, I
•
CH 3 CH 2 OH + HCl CH 3 CH 2 Cl + H 2 O
•
Elimination In the presence of concentrated sulfuric acid and heat an alcohol will eliminate water and form an
alkene;
the reverse of how alcohols are formed.
Addition to Ethylene or Elimination by ALCOHOLS H 2 C CH 2 + H 2 O H 3 PO 4 H 2 SO 4 CH 3 CH 2 OH 70
Forward is an oxidation, the reverse a reduction.
Alcohols can be oxidized to carboxylic acids or ketones 1.
primary
alcohols to aldehydes
with
Oxidizing agents mild O PCC C CH 3 CH 2 OH H 3 C H PCC = N + H CrO 3 Cl -
Pryidinium chlorochromate
Alcohols can be oxidized directly to carboxylic acids or ketones 1.
primary
alcohols directly to acids
oxidizing agents by
STRONG O CrO 3 , H + C CH 3 CH 2 OH H 3 C OH
Alcohols can be oxidized to carboxylic acids or ketones
2. secondary
alcohols to
ketones
OH CH CH 3 2-propanol CH 3 PCC O H 3 C C propanone CH 3
OH CH 3 C CH 3 CH 3 Tertiary alcohols
No reaction
PCC, or CrCl3
Why?
no reaction
CARBONYLCOMPOUNDS
The
carbonyl group
is a carbon atom double bonded to an oxygen atom, and is found in aldehydes, ketones, carboxylic acids, and esters.
O C
Suggest a method for making 76
CARBONYL COMPOUNDS
• • • •
CARBONYL COMPOUNDS
The aldehyde has at least one hydrogen atom bonded the carbonyl carbon. The ketone has two carbon atoms bonded to the carbonyl carbon. The carboxylic acid has an OH bonded to the carbonyl carbon. The ester is a combination of an alcohol and a carboxylic acid.
•
aldehyde, RCOH; ketone, RCOR ' ; carboxylic acid, RCOOH; ester, RCOOR ' .
CARBONYL COMPOUNDS
• • • Carboxylic acids
can be formed by oxidizing primary alcohols or aldehydes. Reducing aldehydes and acids with NaBH LiAlH 4 produces a
primary alcohol.
4 or Reduction of a alcohol.
ketone produces a secondary
Esters
•
Form from carboxylic acids and alcohols when heated with sulfuric acid. They are named from the alcohol and the acid with an ate ending 80
CH 3 CH 2 OH + CH 3 COOH CH 3 COOCH 2 CH 3
Esters
•
In basic solution, esters are hydrolyzed to the alcohol and the salt of the carboxylic acids 81
Alkyl halides RX
• •
React to form alcohols in water using a strong base like NaOH, substitution reaction. In an alcohol solvent, the same reactants form an alkene, elimination reaction.
Alkyl halides
• •
RX react with magnesium metal to form a
Grignard reagent
.
This reagent reacts with aldehydes and ketones to form alcohols and with carbondioxide to form carboxylic acids.
83
Ethers R-O R’
(Additional material) • • Ethers
, R-O-R', can be formed from the reaction of alcohols when heated in the presence of concentrated sulfuric acid. See Lab IVCX 15
11.6 FATS AND OILS
• Fats and oils are esters of glycerol 1, 2, 3-propanetriol • The R group of the triester is a long chain fatty acid.
BOOM!
FATS AND OILS
• Some fats are saturated, some unsaturated, and some are polyunsaturated. • When the triester is hydrolyzed with strong base, the sodium or potassium salt forms and is called a soap. –The process is also called saponfication.
Double bonds Fats Single bonds only Fats
AMINES AND AMIDES
•
React as bases and have bad smells
•
React with carboxylic acids to form
amides
which are similar in structure to esters.
AMINES
AMIDES
Polymers
S U L F U R
11.7 SYNTHETIC POLYMERS
• • Polymers
are formed from combinations of monomers. They can be classified many ways.
–Thermoplastics
can be heated and reformed again and again.
–Thermosetting
plastics are heated and formed, but cannot be heated and reformed because of their high degree of cross-linking.
11.7 SYNTHETIC POLYMERS
•
Another classification system for polymers is based on their intended use: - plastics - fibers
-
Elastomers - coatings - adhesives
•
Polymers can also be classified by the way they form:
–
addition polymers
–
condensation polymers
Addition Polymers
•
The monomers for these polymers all have a double bond.
• •
If an appropriate initiator is added, these monomers can add to the chain one at a time by breaking the double bond.
•
This process is called chain growth polymerization. Copolymers are formed from a mixture of monomers.
Addition: Free Radical 97
Polyethylene: Addition
CH 2 CH 2 CH 2 CH 2 n CH 3 CH CH 2
Polypropylene
CH 3 CH CH 2 n
Branching
(a)
Linear, straight
Polyethylene
Bridging, crosslink
Teflon CF 2 CF 2 CF 2 CF 2 n
What would the following addition polymers look like
O Cl CH CH 2 for PVC C O CH 3 CH 2 CH methyl methacrylate for Lucite, Plexiglass CH CH 2 stryene for styrofoam
PETE (polyethylene terephthalate), HDPE (high density polyethylene), LDPE (low-density polyethylene), PP (polypropylene), CLPE (cross-linked polyethylene, V (vinyl) or PVC, also RLDPE (resin mix, already recycled. The # is another way of identifying that polymer.
Condensation Polymers
• • •
These polymers are usually copolymers. One monomer is a dicarboxylic acid and the other monomer is either a dialcohol or a diamine. These polymers are named as
polyesters
or
polyamides
.
Nylon 66
Polyamide Chains
Monomers Polymer
107