organic chemistry
the chemistry of carbon
on planet earth, all accessible carbon is processed through living organisms
carbon cycle
all available planetary carbon is processed as "organic" carbon over and over
other important elements in organic chemistry
Li,Na, K, Mg, N, Ca, P, O, S, Cl, Br, I
what's the big deal about carbon chemistry?
-there are <16 million known organic compounds(majority of compounds)
-there are in theory an infinite number of organic compounds
-new organic compounds of desired structure are created every day by:
-chemisits/biochemists
-organisms
why is carbon chemistry pervasive?
-carbon forms covalent bonds with itself using single, double, and triple bonds
-carbon forms covalent and/or ionic bonds with >90 elements (no noble gases or highly radioactive elements)
hydrocarbons
compounds containing only Carbon and Hydrogen
universal alkane formula
CnH(2n+2)
n=number of carbons
2n+2=number of hydrogens
rule of four
in stable organic molecules, all carbons have four bonds
Carbon attached to 4 atoms is always sp3 hybridized-tetrahedral geometry
constitutional isomerism
molecules that have the same formula, but different atom-atom connection
different compounds therefore have different physical properties
Naming an alkene
1.) identify the longest chain of carbons
2.) number the chain from 1,2...n such that carbon 1 is assigned to the beginning of the chain and the first branch is minimized
3.) name the alkyl groups and assign their locations using your numbering system
Isobutane
2-methylpropane=IUPAC
Acetylene
Ethyne=IUPAC
1* primary carbon
Carbon attached to one other carbon
2* secondary carbon
Carbon attached to 2 other carbons
3* tertiary carbon
Carbon attached to 3 other carbons
4* quaternary carbon
Carbon attached to 4 other carbons
1* primary hydrogen
Hydrogen attached to 1* carbon
2* secondary hydrogen
Hydrogen attached to 2* carbon
3* tertiary hydrogen
Hydrogen attached to 3* carbon
General cycloalkane formula
CnH2n
Conformations of alkanes
Conformations are structures that interconvert by rotation about carbon-carbon single bonds
Any 3-D arrangement of atoms in a molecule that results by rotation about a single bond
Equivalent term: "conformational isomers"
Carbon-carbon single bonds tend t
Staggered conformation
a conformation about a carbon to carbon single bond in which the atoms on one carbon are as far apart as possible from the adjacent carbon
More stable than eclipsed conformation
Torsion strain
Inherent instability caused by eclipsing
arises when atoms separated by 3 bonds are forced from a staggered conformation to an eclipsed conformation
Cis-trans isomers
isomers that have the same order of attachment of their atoms, but a different arrangement of their atoms in space, due to the presence of either a ring or a carbon-carbon double bond
Cis-trans isomers do not interconnect
They are not constitutional isome
Cis isomers
Have 2 substituents on the same side of the plane
Trans isomers
Have 2 substituents on the opposite sides of the plane
Axial bonds
bond on a chair conformation of a cyclohexane ring that extends from ring parallel to imaginary axis of ring
Straight up and down
3 bonds point up, other three point down
if axial bond on carbon points upward, equatorial bond on that carbon points slightl
Equatorial bonds
bond on chair conformation of cyclohexane ring that extends from the ring roughly perpendicular to the imaginary axis of ring
Directed outward
alternate:1st slightly up and then slightly down
Substituents larger than H prefer to be equatorial
Bigger subst
Physical properties of alkanes
-nonpolar
-soluble in most organic solvents, insoluble in water
-boiling points increase with increasing molecular weight
-when comparing constitutional isomers, the boiling point decreases with greater chain branching--more branched structures=boils at a
Role of dispersion forces for liquid alkanes
Alignment of induced dipoles causes adjacent molecules to stick together
Round or branched alkanes do not align efficiently so they stick together less...smaller area of contact. Therefore lower boiling point
Combustion reaction of an alkane
CnH(2n+2)+((3n+1)/2)O2 --> nCO2+(n+1)H2O
All C become CO2
All H become H2O
Line angle formula
Each line ending represents a carbon atom and a line represents a bond
A carbon at every bend and at every end
Alkyl group
Group derived by removing a hydrogen from an alkane
Given the symbol -R
Iso
For names beyond propane, iso indicates the one end of an otherwise unbranched chain terminates in a (CH3)2CH group
Cycloalkane
Saturated hydrocarbon that contains carbon atoms joined to form a ring
Contains two fewer hydrogen atoms than an alkane with the same number of carbon atoms
IUPAC system of nomenclature
1. Prefix: number carbon atoms in parent chain
2. Infix: nature of C-C bonds in parent chain
-an: all single bonds
-en: one or more double bonds
-yn: one or more triple bonds
3. Suffix: class of compound to which substance belongs
-e: hydrocarbon
-ol: alc
eclipsed conformation
a conformation about a C-C single bond in which the atoms on one carbon are as close as possible to the atoms on the adjacent carbon
angle strain
strain that arises when a bond angle is either compressed or expanded compared with its optimal value
chair conformation
most stable puckered conformation of a cyclohexane ring; all bond angles are about 109.5* and bonds to all adjacent carbons are staggered
-99.9% of all cyclohexanes are in the chair conformation
boat conformation
a puckered conformation of a cyclohexane ring in which carbons 1 and 4 of the ring are bent toward each other
-less stable than chair conformation
-torsional strain is created by 4 sets of eclipsed hydrogen interactions and steric strain created by one se
steric strain
strain that arises when atoms separated by 4 or more bonds are forced abnormally close to one another(forced closer than their atomic radii allow)
chemical property of alkanes and cycloalkanes
interness
quite unreactive toward most reagents(nonpolar and only sigma bonds)
will react with O2(combustion)
major sources of alkanes
fossil fuels (natural gas, petroleum, coal)
organic chemistry
the chemistry of carbon
on planet earth, all accessible carbon is processed through living organisms
carbon cycle
all available planetary carbon is processed as "organic" carbon over and over
other important elements in organic chemistry
Li,Na, K, Mg, N, Ca, P, O, S, Cl, Br, I
what's the big deal about carbon chemistry?
-there are <16 million known organic compounds(majority of compounds)
-there are in theory an infinite number of organic compounds
-new organic compounds of desired structure are created every day by:
-chemisits/biochemists
-organisms
why is carbon chemistry pervasive?
-carbon forms covalent bonds with itself using single, double, and triple bonds
-carbon forms covalent and/or ionic bonds with >90 elements (no noble gases or highly radioactive elements)
hydrocarbons
compounds containing only Carbon and Hydrogen
universal alkane formula
CnH(2n+2)
n=number of carbons
2n+2=number of hydrogens
rule of four
in stable organic molecules, all carbons have four bonds
Carbon attached to 4 atoms is always sp3 hybridized-tetrahedral geometry
constitutional isomerism
molecules that have the same formula, but different atom-atom connection
different compounds therefore have different physical properties
Naming an alkene
1.) identify the longest chain of carbons
2.) number the chain from 1,2...n such that carbon 1 is assigned to the beginning of the chain and the first branch is minimized
3.) name the alkyl groups and assign their locations using your numbering system
Isobutane
2-methylpropane=IUPAC
Acetylene
Ethyne=IUPAC
1* primary carbon
Carbon attached to one other carbon
2* secondary carbon
Carbon attached to 2 other carbons
3* tertiary carbon
Carbon attached to 3 other carbons
4* quaternary carbon
Carbon attached to 4 other carbons
1* primary hydrogen
Hydrogen attached to 1* carbon
2* secondary hydrogen
Hydrogen attached to 2* carbon
3* tertiary hydrogen
Hydrogen attached to 3* carbon
General cycloalkane formula
CnH2n
Conformations of alkanes
Conformations are structures that interconvert by rotation about carbon-carbon single bonds
Any 3-D arrangement of atoms in a molecule that results by rotation about a single bond
Equivalent term: "conformational isomers"
Carbon-carbon single bonds tend t
Staggered conformation
a conformation about a carbon to carbon single bond in which the atoms on one carbon are as far apart as possible from the adjacent carbon
More stable than eclipsed conformation
Torsion strain
Inherent instability caused by eclipsing
arises when atoms separated by 3 bonds are forced from a staggered conformation to an eclipsed conformation
Cis-trans isomers
isomers that have the same order of attachment of their atoms, but a different arrangement of their atoms in space, due to the presence of either a ring or a carbon-carbon double bond
Cis-trans isomers do not interconnect
They are not constitutional isome
Cis isomers
Have 2 substituents on the same side of the plane
Trans isomers
Have 2 substituents on the opposite sides of the plane
Axial bonds
bond on a chair conformation of a cyclohexane ring that extends from ring parallel to imaginary axis of ring
Straight up and down
3 bonds point up, other three point down
if axial bond on carbon points upward, equatorial bond on that carbon points slightl
Equatorial bonds
bond on chair conformation of cyclohexane ring that extends from the ring roughly perpendicular to the imaginary axis of ring
Directed outward
alternate:1st slightly up and then slightly down
Substituents larger than H prefer to be equatorial
Bigger subst
Physical properties of alkanes
-nonpolar
-soluble in most organic solvents, insoluble in water
-boiling points increase with increasing molecular weight
-when comparing constitutional isomers, the boiling point decreases with greater chain branching--more branched structures=boils at a
Role of dispersion forces for liquid alkanes
Alignment of induced dipoles causes adjacent molecules to stick together
Round or branched alkanes do not align efficiently so they stick together less...smaller area of contact. Therefore lower boiling point
Combustion reaction of an alkane
CnH(2n+2)+((3n+1)/2)O2 --> nCO2+(n+1)H2O
All C become CO2
All H become H2O
Line angle formula
Each line ending represents a carbon atom and a line represents a bond
A carbon at every bend and at every end
Alkyl group
Group derived by removing a hydrogen from an alkane
Given the symbol -R
Iso
For names beyond propane, iso indicates the one end of an otherwise unbranched chain terminates in a (CH3)2CH group
Cycloalkane
Saturated hydrocarbon that contains carbon atoms joined to form a ring
Contains two fewer hydrogen atoms than an alkane with the same number of carbon atoms
IUPAC system of nomenclature
1. Prefix: number carbon atoms in parent chain
2. Infix: nature of C-C bonds in parent chain
-an: all single bonds
-en: one or more double bonds
-yn: one or more triple bonds
3. Suffix: class of compound to which substance belongs
-e: hydrocarbon
-ol: alc
eclipsed conformation
a conformation about a C-C single bond in which the atoms on one carbon are as close as possible to the atoms on the adjacent carbon
angle strain
strain that arises when a bond angle is either compressed or expanded compared with its optimal value
chair conformation
most stable puckered conformation of a cyclohexane ring; all bond angles are about 109.5* and bonds to all adjacent carbons are staggered
-99.9% of all cyclohexanes are in the chair conformation
boat conformation
a puckered conformation of a cyclohexane ring in which carbons 1 and 4 of the ring are bent toward each other
-less stable than chair conformation
-torsional strain is created by 4 sets of eclipsed hydrogen interactions and steric strain created by one se
steric strain
strain that arises when atoms separated by 4 or more bonds are forced abnormally close to one another(forced closer than their atomic radii allow)
chemical property of alkanes and cycloalkanes
interness
quite unreactive toward most reagents(nonpolar and only sigma bonds)
will react with O2(combustion)
major sources of alkanes
fossil fuels (natural gas, petroleum, coal)