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Chemistry 122 Introductory Organic Chemistry Spring Quarter 2015 Dr. Thomas H. Schultz.
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Transcript of Chemistry 122 Introductory Organic Chemistry Spring Quarter 2015 Dr. Thomas H. Schultz.
Chemistry 122Introductory Organic Chemistry
Spring Quarter 2015
Dr. Thomas H. Schultz
What is Organic chemistry?
What is Organic chemistry?
The study of carbon and its compounds.
What is Organic chemistry?
The study of carbon and its compounds.
First we will talk about compounds just containing carbon and hydrogen, these compounds are called hydrocarbons.
What is Organic chemistry?
The study of carbon and its compounds.
First we will concentrate on compounds just containing carbon and hydrogen, these compounds are called hydrocarbons.
Hydrocarbon Classification
Hydrocarbons
Alkanes AlkenesCycloalkanes AlkynesCycloalkenes
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H?
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H8 d. C4H?
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H8 d. C4H10
C. Draw Lewis Structures
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H8 d. C4H10
C. Draw Lewis Structures
CH4
C
HH
H
H
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H8 d. C4H10
C. Draw Lewis Structures
CH4 C2H6
C
HH
H
H
CH C
H
H
H
H
H
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H8 d. C4H10
C. Draw Lewis Structures
CH4 C2H6 C3H8
C
HH
H
H
CH C
H
H
H
H
H CH C
H
H
H
H
C
H
H
H
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H8 d. C4H10
C. Draw Lewis Structures
CH4 C2H6 C3H8
D. Polarity? Polar or nonpolar?
C
HH
H
H
CH C
H
H
H
H
H CH C
H
H
H
H
C
H
H
H
1. Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons)
A. General formula of CnH2n+2
B. Examples
a. CH4 b. C2H6 c. C3H8 d. C4H10
C. Draw Lewis Structures
CH4 C2H6 C3H8
D. Polarity? Polar or nonpolar? Nonpolar
C
HH
H
H
CH C
H
H
H
H
H CH C
H
H
H
H
C
H
H
H
E. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
E. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C C
H
HH H
H
H
Butane, C4H10
Primary carbon = ?Secondary carbon = Tertiary carbon =
E. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C C
H
HH H
H
H
Butane, C4H10
Primary carbon = 2Secondary carbon = ? Tertiary carbon =
E. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C C
H
HH H
H
H
Butane, C4H10
Primary carbon = 2Secondary carbon = 2 Tertiary carbon =
E. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C C
H
HH H
H
H
Butane, C4H10
Primary carbon = 2Secondary carbon = 2 Tertiary carbon = ?
G. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C C
H
HH H
H
H
Butane, C4H10
Primary carbon = 2Secondary carbon = 2 Tertiary carbon = 0
E. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C H
H
HC H
H
H
Primary carbon = ?Secondary carbon = Tertiary carbon =
Isobutane C4H10
G. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C H
H
HC H
H
H
Primary carbon = 3Secondary carbon = ? Tertiary carbon =
Isobutane C4H10
E. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C H
H
HC H
H
H
Primary carbon = 3Secondary carbon = 0 Tertiary carbon = ?
Isobutane C4H10
G. Types of carbon 1. Primary (1◦) Carbon connected to one carbon atoms. 2. Secondary (2◦) Carbon connected to two carbon atoms. 3. Tertiary (3◦) Carbon connected to three carbon atoms. 4. How many primary, secondary, and tertiary carbons in the
two different structures of C4H10
C
H
C
H
H
H C H
H
HC H
H
H
Primary carbon = 3Secondary carbon = 0 Tertiary carbon = 1
Isobutane C4H10
1. Alkanes (Continued)
F. There are two different structures for C4H 10 called isomers, because they contain different types of carbon.
Structure 1
Structure 2
C
H
C
H
H
H C H
H
HC H
H
H
Isobutane, C4H10
C
H
C
H
H
H C C
H
HH H
H
H
Butane, C4H10
Constitutional Isomers (Structural Isomers) are different compounds of the same formula. The different structures from the previous slide for the formula C4H10 is an example of Constitutional isomers.
Isomerism
Constitutional Isomers (Structural Isomers) are different compounds of the same formula. The different structures from the previous slide for the formula C4H10 is an example of Constitutional isomers.
How many isomers are there of an alkane containing five carbons (C5H12)?
Isomerism
Isomer Strategy – Draw Lewis possible different length chains of carbons atoms connected with a covalent bond.
Constitutional Isomers (Structural Isomers) are different compounds of the same formula. The different structures from the previous slide for the formula C4H10 is an example of Constitutional isomers.
How many isomers are there of an alkane containing five carbons (C5H12)?
Isomerism
Isomer Strategy – Draw Lewis possible different length chains of carbons atoms connected with a covalent bond.
C C C C C
Chains of 5 carbon atoms
H
H
HH
H HHH
HH
H H
Isomerism
Chains of 4 carbon atoms
C C C C
HH
H HCH
HH
H H
H
HH
Isomerism
Chains of 4 carbon atoms
C
HH
H HCH
HH
H H
H
HH
Chains of 3 carbon atoms
C
C C C
HHH
H
H
HCH
H
H
H
H
H
C C C
Isomerism
Chains of 4 carbon atoms
C C C C
HH
H HCH
HH
H H
H
HH
Chains of 3 carbon atoms
There are three isomers of C5H12
C
C C C
HHH
H
H
HCH
H
H
H H
H
NOMENCLATURE1.Common system
a. Works best for low molecular weight hydrocarbonsb. Steps to give a hydrocarbon a common name:
1. Count the total number of carbon atoms in the molecule.
2. Use the Latin root from the following slide that corresponds to the number of carbon atoms followed by the suffix “ane”.
3. Unbranced hydrocarbons use the prefix normal, or n-, 4. Branched hydrocarbons use specific prefixes, as
shown on a subsequent slide
NOMENCLATURE
Common system Examples
CH C
H
H
H
H
C
H
H
H
1. Give a name for the following compound
Step #1, count the number of carbons and write down the memorized Latin name for that number (next slide)Step #2, since this structure fits the alkane general formula, use the “ane” suffix
propane
Three carbon Latin root
Alkane suffix
Latin Hydrocarbon
RootsNumber of Carbons
LatinRoot
1 meth
2 eth
3 prop
4 but
5 pent
6 hex
7 hept
8 oct
9 non
10 dec
11 undec
Latin Hydrocarbon
RootsNumber of Carbons
LatinRoot
12 dodec
13 tridec
14 tetradec
15 pentadec
16 hexadec
17 heptadec
18 octadec
19 nonadec
20 eicos
21 unicos
22 doicos
C
H
H
H
C
H
C
H
HH
C
H
H
H
CH
H
H
C
CH H
C
HH
H H
H
n-butane
isobutane
H C C C H
H C H
H C H
H
H
H
H H
H
Examples
neopentane
2. Systematic System of Nomenclature (IUPAC)
•Find the longest continuous chain of carbon atoms.•Use a Latin root corresponding to the number of carbons in the longest chain of carbons.•Follow the root with the suffix of “ane” for alkanes•Carbon atoms not included in the chain are named as substituents preceding the root name with Latin root followed by “yl” suffix.•Number the carbons, starting closest to the first branch.•Name the substituent's attached to the chain, using the carbon number as the locator in alphabetical order.•Use di-, tri-, etc., for multiples of same substituent.• If there are two possible chains with the same number of carbons, use the chain with the most substituent's.
Substituent Names (Alkyl groups)
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
Which one?
Systematic Nomenclature continued.
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
Which one?
Systematic Nomenclature continued.
The one with the most number of substituent's
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
Which one?
Systematic Nomenclature continued.
The one with the least number of substituent's
The top structure has four substituent's and the bottom has threesubstituent's.
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
Which one?
Systematic Nomenclature continued.
The one with the least number of substituent's
The top structure has four substituent's and the bottom has threesubstituent's.
Name = ?
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
Which one?
Systematic Nomenclature continued.
The one with the most number of substituent's
The top structure has four substituent's and the bottom has threesubstituent's.
Name = ? heptane
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
Which one?
Systematic Nomenclature continued.
The one with the least number of substituent's
The top structure has four substituent's and the bottom has threesubstituent's.
Name = 3,3,5-trimethyl-4-propylheptane
CHH3C
CH3
CH
CH2CH3
CH2 CH2 CH
CH3
CH3
Another Example:
Name = 3-ethyl-2,6-dimethylheptane
CHH3C
CH3
CH
CH2CH3
CH2 CH2 CH
CH3
CH3
Another Example:
Name = 3-ethyl-2,6-dimethylheptane
Notice substituent's are in alphabetical order; di, tri, etc. do not participate in the alphabetical order
Line StructuresA quicker way to write structures'
CHH3C
CH3
CH
CH2CH3
CH2 CH2 CH
CH3
CH3 (Condensed Structure)
(A line structure of the above condensed structure)
ethyl
methyl
methyl
Complex Substituent's•If the branch has a branch, number the carbons from the point of attachment.•Name the branch off the branch using a locator number.•Parentheses are used around the complex branch name.
1-methyl-3-(1,2-dimethylpropyl)cyclohexane
12
13
Alkane Physical PropertiesSolubility: hydrophobic (not water soluble)Density: less than 1 g/mL (floats on water)
Boiling points increase with increasing carbons (little less for branched chains) due to dispersion forces being larger.
Melting points increase with increasing carbons (less for odd-number of carbons).
Boiling Points of AlkanesBranched alkanes have less surface area contact,so weaker intermolecular forces.
Melting Points of AlkanesBranched alkanes pack more efficiently into a crystalline structure, so have higher m.p.
Reactions of AlkanesI. Combustion reaction
CH
H
H
H + O2
heatCO2 + H2O
+ O2
heatCO2 + H2O
II. Cracking reactionheat
catalyst
+
III. Halogenation reaction (substitution reaction)
+ Cl2
+ HCl+
Cl Cl
Butane 2-chlorobutane 1-chlorobutane
sun
Sample problem: Which isomer of C5H12 has the most monochloro isomers?
Problem solving process:Step 1 draw the isomers of C5H12
Step 2 react each isomer with chlorineStep 3 count the products
Sample problem: Which isomer of C5H12 has the most monochloro isomers?
Problem solving process:Step 1 draw the isomers of C5H10
Step 2 react each isomer with chlorineStep 3 count the products
+ Cl2
+ Cl2
+ Cl2
Sample problem: Which isomer of C5H12 has the most monochloro isomers?
Problem solving process:Step 1 draw the isomers of C5H10
Step 2 react each isomer with chlorineStep 3 count the products
+ Cl2
+ Cl2
+ Cl2
Cl
Cl
Cl
+ +
2-chloropentane 1-chloropentane 3-chloropentane
Sample problem: Which isomer of C5H12 has the most monochloro isomers?
Problem solving process:Step 1 draw the isomers of C5H10
Step 2 react each isomer with chlorineStep 3 count the products
+ Cl2
+ Cl2
+ Cl2
Cl
Cl
Cl
+ +
2-chloropentane 1-chloropentane 3-chloropentane
Cl
ClCl
Cl
1-chloro-3-methylbutane 2-chloro-3-methylbutane 2-chloro-2-methylbutane 1-chloro-2-methylbutae
Sample problem: Which isomer of C5H12 has the most monochloro isomers?
Problem solving process:Step 1 draw the isomers of C5H10
Step 2 react each isomer with chlorineStep 3 count the products
+ Cl2
+ Cl2
+ Cl2
Cl
Cl
Cl
+ +
2-chloropentane 1-chloropentane 3-chloropentane
Cl
ClCl
Cl
1-chloro-3-methylbutane 2-chloro-3-methylbutane 2-chloro-2-methylbutane 1-chloro-2-methylbutae
Cl
1-chloro-2,2-dimethylpropane
Sample problem: Which isomer of C5H12 has the most monochloro isomers?
Problem solving process:Step 1 draw the isomers of C5H10
Step 2 react each isomer with chlorineStep 3 count the products
+ Cl2
+ Cl2
+ Cl2
Cl
Cl
Cl
+ +
2-chloropentane 1-chloropentane 3-chloropentane
Cl
ClCl
Cl
1-chloro-3-methylbutane 2-chloro-3-methylbutane 2-chloro-2-methylbutane 1-chloro-2-methylbutae
Cl
1-chloro-2,2-dimethylpropane
Winner!
Conformers of Alkanes
•Structures resulting from the free rotation of a C-C single bond•May differ in energy. The lowest-energy conformer is most prevalent.•Molecules constantly rotate through all the possible conformations.
Ethane ConformersStaggered conformer has lowest energy.Dihedral angle = 60 degrees
model
H
H
H
H
H H
Newmanprojection sawhorse
Dihedral angle
Ethane Conformers (2)Eclipsed conformer has highest energyDihedral angle = 0 degrees
=>
Conformational Analysis•Torsional strain: resistance to rotation.•For ethane, only 12.6 kJ/mol
=>
Propane ConformersNote slight increase in torsional straindue to the more bulky methyl group.
Butane Conformers C2-C3Highest energy has methyl groups eclipsed.Steric hindranceDihedral angle = 0 degrees
=>totally eclipsed (methyl groups)
Butane Conformers (2)Lowest energy has methyl groups anti.Dihedral angle = 180 degrees
=>Staggered-anti
Butane Conformers (3)•Methyl groups eclipsed with hydrogens•Higher energy than staggered conformer•Dihedral angle = 120 degrees
=>Eclipsed (hydrogen and methyl)
Butane Conformers (4)•Gauche, staggered conformer•Methyls closer than in anti conformer•Dihedral angle = 60 degrees
=>Staggered-gauche
Conformational Analysis
Cycloalkanes
•Rings of carbon atoms (-CH2- groups)
•Formula: CnH2n
•Nonpolar, insoluble in water•Compact shape•Melting and boiling points similar to branched alkanes with same number of carbons•Slightly unsaturated compared to alkanes
Naming Cycloalkanes•Count the number of carbons in the cycle•If the bonds are single then use the suffix “ane”•First substituent in alphabet gets lowest number.•May be cycloalkyl attachment to chain.
cyclopropane cyclobutane cyclopentane cyclohexane cycloheptane
mehtylcyclopropane 1-ethyl-2-methylcyclobutane
CH3 H3CH2C CH3
2-cyclopropylheptane
Cis-Trans Isomerism(a type of stereoisomerism)
Cis: like groups on same side of ringTrans: like groups on opposite sides of ring
Cycloalkane Stability• 6-membered rings most stable• Bond angle closest to 109.5• Angle (Baeyer) strain• Measured by heats of combustion per -CH2 -
Heats of Combustion/CH2 Alkane + O2 CO2 + H2O
658.6
697.1 686.1664.0 663.6 kJ/mol
662.4658.6 kJ
Long-chain
Cyclopropane
• Large ring strain due to angle compression• Very reactive, weak bonds
=>
Cyclopropane (2)
Torsional strain because of eclipsed hydrogens
Cyclobutane• Angle strain due to compression• Torsional strain partially relieved by ring puckering
=>
Cyclopentane• If planar, angles would be 108, but all hydrogens would be eclipsed.• Puckered conformer reduces torsional strain.
Cyclohexane• Combustion data shows it’s unstrained.• Angles would be 120, if planar.
• The chair conformer has 109.5 bond angles and all hydrogen's are staggered.
• No angle strain and no torsional strain.
Chair Conformer
Boat Conformer
Conformational Energy
Axial and Equatorial Positions
Monosubstituted Cyclohexanes
1,3-Diaxial Interactions
Disubstituted Cyclohexanes
Cis-Trans IsomersBonds that are cis, alternate axial-equatorial around the ring.
=>
CH3
CH3
One axial, one equatorial
Bulky Groups• Groups like t-butyl cause a large energy difference between the axial and equatorial conformer. • Most stable conformer puts t-butyl equatorial regardless of other substituents.
=>
End of Chapter 2