Organic Part 2 - Chemistry...
Transcript of Organic Part 2 - Chemistry...
Mary J. Bojan Chem 110
Organic Part 2 Hydrocarbons
1. Alkanes: all single bonds 2. Alkenes: C=C
saturated v. unsaturated structural isomers geometric isomers
3. Alkynes: C≡C 4. Aromatic hydrocarbons
Reactivity of hydrocarbons • addition reactions • combustion reactions
Petroleum
1
Mary J. Bojan Chem 110
Hydrocarbons
This is the structure of 4-ethyl-2,3,3-trimethylnonane
What is the molecular formula of this compound?
How many ⎯CH3 groups are there on this compound?
2
Mary J. Bojan Chem 110
HYDROCARBONS Simplest organic compounds
Contain only C and H
Alkanes saturated have the maximum number of H attached to the C skeleton.
Alkenes unsaturated Alkynes have double or Aromatic triple bonds
3
Mary J. Bojan Chem 110
ALKENES Contain one or more double bonds
The C=C⎯H or C=C⎯C angle is 120°
CnH2n
Rotation about double bond is restricted
propene ethene (ethylene)
C C
CH
H
H
HC
4
CH
H
H
CH3
C
Mary J. Bojan Chem 110
Butene C4H8 There are several possible structures for a chain of 4 carbons with one double bond.
1-butene 2-methylpropene
2-butene
cis-2-butene trans-2-butene 5
Mary J. Bojan Chem 110
Structural isomers: same molecular formula: different structure
1-butene 2-methylpropene 2-butene
Structural vs. Geometric
6
Geometric isomers same molecular formula: different geometry
cis-2-butene trans-2-butene
cis-isomer: same side trans-isomer: opposite side (across)
Mary J. Bojan Chem 110
ALKYNES: CnH2n-2 Contain ⎯C≡C⎯
H⎯C≡C⎯H CH3⎯C≡C⎯H ethyne propyne
(acetylene) bond angle is 180°
structural isomers no geometric isomers are possible
7
C C HC
H
H
C
H
H
H
C C CC
H
H
H
H
H
H
1-butyne 2-butyne
Mary J. Bojan Chem 110
Reactions of Alkenes and Alkynes Addition reaction
– Double and triple bonds are reactive: addition reactions typically occur at room temperature.
8
For Alkenes CH3⎯CH=CH2 + Br2 →
or CH3⎯CH=CH⎯CH3 + HX →
where X = Cl, Br, I, OH, etc.
For Alkynes
CH3 ⎯C≡CH + 2Br2 →
CH3-C ≡C -CH3 + 2HCl →
Mary J. Bojan Chem 110
Aromatic Hydrocarbons Contain alternating single and double C-C Bonds
Benzene is prototypical molecule
Usually written:
Aromatic hydrocarbons are less reactive than alkenes:
Special kind of bonding Have “delocalized” π electrons Results in added stability
9
CCC
CCC
HH
HH
H
H CCCCCC
HH
HH
H
H
Mary J. Bojan Chem 110
Reactivity of Hydrocarbons Same reaction: hydrocarbon + Br2
Colorless red
10
CH3
ALKANE Heptane + Br2 ⎯→
ALKENE (and ALKYNES)
2-pentene + Br2 ⎯→
AROMATIC
toluene + Br2 ⎯→
Mary J. Bojan Chem 110
Functional Group classes Contain a representative group of elements in a fixed pattern
Have similarities in structure and function (reactivity).
11
Seemingly small changes in structure can have big affect on molecular properties
Functional Group Type hydrocarbon alcohol ether CH3⎯CH2⎯H CH3⎯CH2⎯O H CH3⎯O⎯CH3
ethane ethanol di-methyl ethe r g a s liquid g a s
bp –89°C bp 78°C bp –24 °C water soluble
Example: adding an oxygen changes a hydrocarbon into an alcohol or an ether…
Mary J. Bojan Chem 110
Functional Group Classes Contain a representative group of elements in a fixed pattern:
Each class has similarities in structure and function (reactivity).
12
Groups which have
a carbonyl
Aldehydes Ketones (R,R’≠H)
Alcohols R-OH R≠H
R = alkyl group
Ethers R-O-R’ R,R’≠H
Amines
N HHR
N R'HR
N R'RR"
CO
RC
H
O
R'C
R
O
Carboxylic Ester Amide Acid
OHC
R
O
OR'C
R
O
NHR'C
R
O
Mary J. Bojan Chem 110
Functional Groups with O and N
Alcohols R⎯OH hydroxyl group
hydrocarbon (alkyl) group
Ether R⎯O⎯R’
13
N HHR
N R'HR
N R'RR"
Amines
Mary J. Bojan Chem 110
Functional Groups Containing the carbonyl group
Aldehyde
Ketone
Carboxylic Acids ⎯COOH
14
C O
RC
H
O
R'C
R
O
OHC
R
O
Mary J. Bojan Chem 110
Organic Acids and Bases
AMINES weak bases, organic bases (like NH3)
(CH3)3N(aq) + H+(aq) (CH3)3NH+(aq)
CARBOXYLIC ACIDS weak acids, organic acids
(aq) (aq) + H+(aq)
15
HOC
RO
-OC
RO
Mary J. Bojan Chem 110
Questions Which of the following hydrocarbon classes does NOT have a double or triple bond?
1 alkane 2 alkene 3 alkyne 4 aromatic
Which one of the following functional group classes does not have a double bond?
1 aldehyde 2 Ketone 3 amine 5 ester
16
Mary J. Bojan Chem 110
The presence and properties of functional groups are responsible for the action of drugs.
What functional groups are present in these molecules?
Acetyl salicylic acid Acetaminophen
Ibuprofen
17
C
O
O C
O
OH
CH3
HO N
H
C
O
CH3
CH3
O
OH
H3C
CH3
Mary J. Bojan Chem 110
What’s Next?
• Formulas tell us how atoms are connected to each other
• Lewis structures tell us where the electrons are.
QUESTIONS • What are the shapes of these molecules? • Can we use information about bonding,
connectivity of atoms, molecular formulas, etc. to predict the shapes (and properties) of molecules?
18