Transcript chapter24_Students_Organicx

Lecture Presentation
Chapter 24
The Chemistry of
Life: Organic and
Biological Chemistry
James F. Kirby
Quinnipiac University
Hamden, CT
© 2015 Pearson Education, Inc.
Organic Chemistry and Biochemistry
Chapter focus on the molecules that bridge chemistry and biology.
Most common elements: C, H, O, N
Organic chemistry: Study of compounds containing carbon.
Biochemistry: study of chemistry of living systems.
24.1 General Characteristics of Organic Molecules
Carbon can have a maximum of 4 bonds.
4 single bonds: tetrahedral, sp3 hybridized.
1 double bond: trigonal planar, sp2 hybridized.
1 triple bond: linear, sp hybridized.
C—H are most common in organic molecules.
C forms stable (strong) bonds with many
elements, including C, H, O, N, and the halogens.
Groups of atoms that determine how an
organic molecule reacts are called
functional groups.
24.2-24.3 Hydrocarbons
Alkanes (CnH2n+2) – only C−C single bonds
CH3–CH2–CH2–CH3
Alkenes (CnH2n) – one or more C−C double bonds
CH3–CH2–CH=CH2
Alkynes (CnH2n-2) – one or more C−C triple bonds
CH3–CH2–CΞCH
Remember: Carbon can have a maximum of 4 bonds.
24.2-24.3 Hydrocarbons
Cyclic Alkanes (CnH2n)
C6H12
C4H8
C3H6
– ring, only C−C single bonds
cyclopropane
cyclobutane
cyclohexane
Isomerism: Same formula but different bonds
C4H10
C4H10
n-butane
2-methylpropane
isobutane
24.2-24.3 Hydrocarbons
Aromatic hydrocarbons – ring, alternating double/triple and single bonds
The simplest aromatic hydrocarbon is benzene (C6H6).
24.2-24.3 Hydrocarbon Nomenclature
IUPAC Rules of Naming Alkanes
1. For alkanes, add –ane to the Greek root for the number of carbons.
CH3–CH2–CH2–CH2–CH2–CH3
hexane
2. Alkyl substituents: drop the –ane and add –yl.
C2H6
C2H5
ethane
ethyl
24.2-24.3 Hydrocarbons
increasing
molar mass
increasing
mp
increasing
bp
24.2-24.3 Hydrocarbons: Nomenclature
Alkyl Substituents
Used when the alkyl part is not in
the longest hydrocarbon chain.
24.2-24.3 Hydrocarbons: Nomenclature
IUPAC Rules of Naming Alkanes
Prefix−Parent−Suffix
What
substituents?
How many
carbons?
What family?
1. Find the parent (longest) hydrocarbon.
2. Number the atoms in the chain sequentially as such substituents are at
lowest possible number along the chain.
CH3
CH3–CH2–CH–CH2–CH2–CH3
1
2
3
4
5
3-methylhexane
6
3. Substituents are named in alphabetical order and use di–, tri–, etc.
CH3 CH3
CH3–CH2–CH–CH2–CH2–CH3
1
2
3
4
5
6
3,4-dimethylhexane
EXERCISE #1
Name the following compounds:
CH3
a)
H3C C
1 2
CH3
CH2 CH
3
4
CH3
3
H3C C
2
5
CH3
6
CH3
CH2 CH3
b)
CH2
4
5
CH2 CH2
1
CH2 CH3
2,2,4,5-tetramethylhexane
CH2 CH3
6
CH
7
8
CH2 CH3
3,6-diethyl-3-methyloctane
24.2-24.3 Hydrocarbons: Nomenclature
IUPAC Rules of Naming Alkenes
Prefix−Parent−Suffix
1. For alkenes, add –ene to the Greek root for the number of carbons.
C2H4
ethene
2. With more than 3 carbons, double bond is indicated by the lowest–
numbered carbon atom in the bond.
CH3–CH=CH–CH2–CH3
1
2
3
4
5
2–pentene
24.2-24.3 Hydrocarbons: Nomenclature
Prefix−Parent−Suffix
IUPAC Rules of Naming Alkynes
Same as for alkenes except use –yne as suffix.
C2H2
ethyne
CH3–CH2–CΞC–CH2–CH2–CH2–CH3
1
2
3 4 5
6
7
8
3–octyne
EXERCISE #2
Name the following compounds:
CH3
CH3
a) H3C CH CH2 C
6
5
4
3
C
2
b)
1
2,3,5-trimethyl-2-hexene
CH3
2
CH3
1
CH2 CH3
3
H3C C
4
CH
5
CH2
CH2 CH3
6
CH
7
CH2
8
CH3
6-ethyl-3-methyl-3-octene
24.4 Organic Functional Groups
Functional group
An atom or a group of atoms
attached to a hydrocarbon.
EXERCISE #3
Identify the functional group in the following hydrocarbon.
a)
b)
c)
alcohol, ROH
ether, ROR’
ester, RCOOR’
24.6 Introduction to Biochemistry
Biomolecules
● Biopolymers (large biological molecules built from small molecules.
● Proteins
● Polysaccharides (carbohydrates)
● Nucleic acids
● Lipids are large molecules, but are not polymers.
24.7 Proteins
Proteins (polypeptides)
Biopolymers made up of
monomers called amino acids.
Biomolecules with molar masses
~ 6000 to > 1,000,000 g/mol.
H
H2N
C
R
COOH
C = α-carbon
R = side chains
There are 20 amino acids commonly found in proteins.
Peptide bond
24.7 Proteins
20 natural a-amino
acids that make up
proteins
24.7 Proteins
Protein structure
Primary structure: the
sequence of amino acids in
a polypeptide strand.
Secondary structure:
a-helix formed from C＝O
and N—H interactions
between side-chains in a
strand.
b-sheets formed from
interactions between
amide H of one strand and
carbonyl O of another
strand.
24.7 Proteins
Protein structure
Tertiary structure: gives
the 3D structure of
proteins. Tertiary
structure is formed from
interactions between
side-chains of multiple
strands.
Quaternary structure:
arrangement of multiple
tertiary structures and/or
incorporation of nonamino acid portions of
proteins.
24.8 Carbohydrates
Carbohydrates
Biopolymers made up of
monomers e.g. glucose,
fructose, and/or galactose.
The name comes from an
empirical formula for
sugars: Cx(H2O)y—for the
simplest sugars, x = y.
glucose
Sucrose (table sugar)
Glycoside
bond
Starch (energy source)
Cellulose (cell wall)
24.9 Lipids
Lipids
Nonpolar, water insoluble biomolecules.
Our energy storage (fats, oils) and building blocks in biological
structures (phospholipids in cell membranes).
Fats and oils are made from glycerol and long-chain carboxylic acids.
Fats have only saturated carboxylic acids.
Oils have at least one unsaturated carboxylic acid.
Phospholipids are made from glycerol with ester linkage to two fatty
acids, and phosphate ester linkage to one polar or charged group, such
as choline.
24.9 Lipids
Comparing Fats to Phospholipids
24.10 Nucleic Acids
Nucleic acids
Biopolymers made up of monomers
nucleotides.
DNA (deoxyribonucleic acid) stores and
transmits genetic information,
responsible for protein synthesis.
Molar masses of several billion g/mol.
deoxyribose
RNA (ribonucleic acid) helps in protein
synthesis.
Molar masses 20,000 – 40,000 g/mol.
OH
ribose
22.6 – Natural Polymers
Organic bases in DNA and RNA
DNA
RNA
OH
End of Chapter 24