Transcript Chapter 1 Structure and Bonding

Chapter 20 Organic Chemistry
I.
What is Organic Chemistry?
A.
B.
C.
D.
E.
Organic Chemistry = chemistry of carbon containing (organic) molecules
Most Familiar compounds are “organic”
1) Cotton in clothing
4) Plastics
2) Gasoline
5) Drugs
3) Food
6) Dyes
Natural Products vs. Synthetic Organic compounds
1) Natural Products are compounds we find in the environment
a) May need to be refined or isolated from the source
b) Are starting materials for synthetic compounds
2) Synthetic Organic compounds do not occur naturally and must be
O
synthesized from simpler compounds
CH3
CH3
N
Caffeine: an important organic molecule
N
Hydrocarbons: simplest organic molecules
N
O
N
CH3
II.
Alkanes
A.
Structure (Carbon always has four bonds)
1) Hydrocarbons = molecules containing only hydrogen and carbon atoms
2) Saturated = hydrocarbon containing all of the hydrogen possible (all single bonds)
3) Unsaturated = hydrocarbon with less than maximum H’s (double/triple bonds)
Unsaturated
= Alkene
Saturated
= Alkane
4)
5)
6)
Normal Alkanes = straight chain, with no branching
Branched Alkanes = no longer just one chain; main chain has “branches”
Structural Isomers = same chemical formula, but different order of attachment; straightchain and branched alkanes are structural isomers of each other
C4H10
B.
C4H10
Nomenclature: systematic naming by IUPAC rules
1) Straight Chain Alkanes
a) C1 = Methane C2 = Ethane
C3 = Propane
b) C5-C10 = pent-, hex-, hept-, oct-, non-, dec- -ane
Generic Formula:
CnH2n+2
C4 = Butane
2) Rules for naming Branched Alkanes (or drawing structure from name)
1. Find the longest chain and name it as a straight chain alkane
2. Name substituents as alkyl groups
3. Number the main chain starting from the end closest to a substituent
4. Write the name
i. Alphabetize by sub. (di-, tri-count only if part of sub. name)
ii. Order #’s from low to high; use smallest possible numbers
iii. Capitalize the first letter only
iv. Write as one word with commas and hyphens as needed
v. Complex substituents in parentheses
1
1
5-Ethyl-2,2-dimethyloctane
1’
4-ethyl-3,6-dimethyldecane
1
1
5-(1,1-Dimethylethyl)-3-ethyloctane
4-(1-Ethylpropyl)-2,3-dimethylnonane
C.
Cycloalkanes
CH3
CH3
CH2
1)
2)
3)
4)
5)
D.
CH2
cyclopentane
Remove 2 terminal H’s and join the terminal carbons
General formula = CnH2n
Names: prefix cyclo- is added to the n-alkane name
methylcyclohexane
Homologous series as ring size increases by CH2
ethylcyclobutane
Not Structural Isomers of other alkanes, because different formulas
Reactions of Alkanes
1) Not very reactive; all bonding positions occupied by H
2) Combustion Reactions: Always make CO2 and H2O
CH3CH3 + 7/2O2 -----> 2CO2 + 3H2O
Important as energy sources: gasoline contains alkanes (octane)
3)
4)
Substitution Reactions: by halogens to make haloalkanes
CH4 + Cl2 -----> CH3Cl + HCl (Chloromethane)
New Functional Group Haloalkanes = replace H with F,Cl,Br,I on an alkane
Dehydrogenation Reactions: removing H makes unsaturated hydrocarbons
Cr2O3, 500 oC
H
H
III. Alkenes
A.
Structure: Hydrocarbons containing at least one double bond
1) Generic formula = CnH2n
cis-2-butene
2
3
2) Hybridization is sp , rather than the sp hybridization of alkanes
trans-2-butene
B.
C.
3) Can have cis and trans isomers
Nomenclature
1) Name similarly to the alkanes, but with an –ene ending (Ethene, not Ethane)
2) Indicate the position of the double bond with a number (Structural Isomers)
CH2=CHCH2CH3 is 1-butene
CH3CH=CHCH3 is 2-butene
3) Stereoisomers = same formula/attachment, different spatial orientation (cis/trans)
Reactions
1) Addition Reactions = carbons can add atoms because of unsaturation
catalyst
Hydrogenation: CH2=CHCH3 + H2 --------> CH3CH2CH3
Halogenation: CH2=CHCH3 + Br2 --------> CH2BrCHBrCH3
IV. Alkynes
A.
CH3CCCH3
Structure: Hydrocarbons containing at least one triple bond
1) Generic formula = CnH2n-2
2) Hybridization is sp, rather than the sp2 hybridization of alkenes
B.
Nomenclature
1) Name similarly to the alkenes, but with an –yne ending (Ethyne, not Ethene)
2) Indicate the position of the triple bond with a number (Structural Isomers)
a) HCCCH2CH3 is 1-butyne
b) CH3CCCH3 is 2-butyne
Reactions
1) Addition Reactions = carbons can add atoms because of unsaturation
a) Hydrogenation: HCCCH3 + 2H2 catalyst
--------> CH3CH2CH3
C.
b)
Halogenation: HCCCH3 + 2Br2 --------> CHBr2CBr2CH3
V.
Aromatic Hydrocarbons
A.
Structure: must contain a six-membered ring having three double bonds
B.
1) Benzene is the simplest aromatic; sp2 hybridization at every carbon
2) There are two equivalent resonance forms; a circle in the center is a shortcut
Nomenclature: number and name the substituents as prefixes to “benzene”
1) There are three structural isomers of disubstituted benzenes
2) An older system called them ortho-, meta-, and para-
C.
Reactions
1) Very unreactive compared to other hydrocarbons: resonance stabilization
2) Substitution of hydrogen atoms is possible with the right catalysts
FeCl3
AlCl3
+ CH3Cl
+ Cl2
Cl
VI. Alcohols, Aldehydes, and Ketones
A.
B.
C.
CH3CH2CH2OH
Structure of Alcohols: replace an -H on a hydrocarbon with an –OH
1-butanol
Primary alcohol
Short chain alcohols are water soluble (Hydrogen Bonding)
Most hydrocarbons are not water soluble because they are non-polar
Nomenclature
OH
OH
1) Modify the alkane name by dropping –e and adding
–ol
2) Name based on longest chain containing -OH
4-methly-3-propyl-2-octanol
3) Number each carbon starting from3-methylheptanol
the closest to –OH
Secondary alcohol
Reactions: Oxidation to Aldehydes and Ketones
1) Classifying alcohols: Primary at the end of a chain; Secondary within the chain
2) An Aldehyde is an oxidized Primary Alcohol (reduced aldehyde)
O
oxidation
RCH2OH
3)
4)
reduction
R
C
H
A Ketone is an oxidized Secondary Alcohol (reduced ketone)
R'
CH OH
R
Na2Cr2O7
H2SO4, H2O
R'
C
R
O
Aldehydes are named with –al endings, Ketones are named with –one endings
VII. Carboxylic Acids and Derivatives
A.
B.
Structure: Carboxylic Acids contain an O=C—OH ; a complicated functional group
Nomenclature
1) Assign number 1 to carboxy carbon and number longest chain including it
2) Replace –ane ending of an alkane with –oic acid ending
Cl
3) Carboxylic acids have priority over any other functional group studied
O
Br
OH
OH
1-bromo-2-chlorocyclopentanecarboxylic acid
O
O
5-methyl-6-heptenoic acid
C.
COOH
3-methyl-4-oxopentanoic acid
Reactions: Carboxylic Acids can become several related functional groups
1) Addition-Elimination Reaction: New molecule adds, while OH leaves
O
O
O
SOCl2
H3C
Cl
H3C
Acyl Halide
CH3OH
H3C
OH
Carboxylic Acid
NH3
O
H3C
H3C
Ester
O
O
O
O
O
Anhydride
CH3
OH
H3C
NH2
Amide
CH3
H
VIII. Amines and Ethers
A.
Amines are derivatives of Ammonia, in which hydrogen is replaced by alkyl groups
1) Primary Amine: Only one H atom is replaced
NH2
2)
Butylamine
Secondary Amine: Two H atoms are replaced
Ethylmethylamine
N
H
B.
C.
3) Tertiary Amine: All three H atoms are replaced
NH
Can be Aromatic or Heteroaromatic
N
Basic due to nitrogen lone pair
Triethylamine
2
Aminobenzene (Aniline)
D.
N
Pyridine
Ethers are Derivatives of Water, in which both Hydrogens are replaced by alkyl groups
1) Related to alcohols, in which only one H atom of water is replaced
2) Fairly Unreactive; Similar polarity to the alkanes, unless very small
3) Non-polar and unreactive—much like alkanes
O
Diethyl Ether
O
MTBE = methyl-tert-butyl ether
VIII. Polymers
A.
B.
Long-chain molecules built from many small molecule units (monomers)
1) Plastics, synthetic fibers (nylon), and many other materials are polymers
2) One of the most important chemical discoveries effecting daily life
Types of Polymerizations
1) Addition Polymerization = identical monomers add together with no biproducts
C C
C
C C
C
C C C C C C
monomer
polymer
Polymers based on alkenes are common examples
CH3
H2C
C
CH3
+
H
H3C C
CH3
2)
C
H2C
CH3
C
H3C C
CH3
CHO3
CH2 C
HOCH2CH2OH +
CH3
+
CH2 C
CH3
CH3
CH3
HO
CH3O
+
H2C
O
H3C
C
CH3OH
CH2CH2O
CH3
CH3
C
CH3
O
CH2
CH3
+ H2O
3)
CH3
Condensation Polymerization = two molecules add, with a biproduct given off
CH3
H3C
CH3
CH3
C
CH2 C
CH3O
CH3
Dacron Polyester
Co-polymer = 2 different monomers, Homopolymer = 1 type of monomer