Transcript CHAPTER 25 - CARBON AND ITS COMPOUNDS

CHAPTER 25 - CARBON
AND ITS COMPOUNDS
Organic - pertaining to life
Living or was once living
Organic Chemistry - The chemistry of
carbon compounds
Carbon is well suited for life because it is
the most versatile element in terms of
bonding.
Carbon can form four bonds.
They can be single, double or triple bonds.
Carbon will not form diatomic molecules
like other small atoms do.
It can form long carbon chains containing
strong, short, covalent bonds.
Allotropes
forms of the same element that differ in
their bonding
There are several allotropes of carbon
Diamond – tetrahedral network of carbon
atoms (every atom is locked into place
(hardness)
Graphite – sheets can slide over each
other (lubricant)
Amorphous carbon – charcoal, soot, coke
Amorphous has not set arrangement of
atoms. It has irregular patterns of high
surface area, deep “caves” that can trap
other molecules
Fullerenes – spherical molecules (60
atoms) see page 807, mostly
experimental at this point.
Hydrocarbons
molecules that contain only hydrogen
and carbon
Fossil Fuels
Natural gas - mostly methane
Crude oil - mixture of hydrocarbon chains
from propane to butane, octane and
longer Components separated using
fractional distillation (see page 823)
Coal - mostly impure carbon (coke - pure
carbon from coal, charcoal - pure carbon
from wood)
Types of Formulas (examples)
Compound - hexane
Empirical formula
Molecular formula
Structural formula
Condensed structural formula
CLASSIFICATION OF ORGANIC
COMPOUNDS
ALKANES - Compounds that contain only
hydrogen and single bonded carbons.
(carbon chains surrounded by hydrogens)
Named with an ane ending that is
preceded with a prefix which gives how
many carbons that are in the carbon chain.
Memorize the IUPAC prefixes on page 816
BRANCHED ALKANES
Give the name of the branch with a yl
ending.
Indicate the number of the branch (keep
numbers as low as possible).
Examples:
Problem assignment # 1 (first side of
sheet)
ALKANES SUBSTITUDED WITH
HALOGENS
Give the position of the halogen (F, Cl,
Br, or I) and then give the name of the
halogen with an "o" ending.
3-chloro-2-methylpentane
bromochloroiodomethane
Conformational isomers - molecules with
the same structure but with different bond
rotation.
Molecules with single bonds can rotate
about the single bond.
These are the same compound. They
have the same melting point, the same
boiling points and the same chemistry.
The higher the temperature the faster
they change back and forth from one
form to the other.
Example: cyclohexane (chair and boat
conformation)
http://www.chem.ucalgary.ca/courses/351/
Carey5th/Ch03/ch3-06.html
Structural isomers - molecules that have
the same molecular formula but have
different structural formulas.
These are different compounds with
different melting points and different
chemistry
Examples C5H12 (pentane, 1 methyl
butane, 2,2 dimethyl propane)
SUBSTITUTED ALKANES
Fisher Projection - a way to show the 3dementional character of a molecule.
Examples: CHFClI
A carbon that has 4 different groups
bonded to it is called a chiral carbon.
Enantiomers - (mirror image isomers) two arrangements around a chiral carbon
that cannot be rotated in such a way as to
be superimposed on each other.
They are different molecules that have
the same formula, same boiling points
and much of the same chemistry.
Their chemistry differs when they are
reacting with molecules that also have
chiral carbons. (biological systems)
They also rotate polarized light in
opposite directions.
Vitamin C is an example of this type of
molecule.
UNSATURATED
HYDROCARBONS
If the molecule is filled to capacity with
hydrogen the compound is saturated
(alkanes).
If the molecule is cyclic, contains a
double bond or contains a triple bond
it is unsaturated.
Saturated fats are from animals and
are not good for you.
Unsaturated fats are from plants.
Alkenes - contains a double bond.
Alkynes - contains a triple bond.
Use the same prefixes along with a
number to give the position of the
double or triple bond.
Example: 1 propene, 1 propyne,
3 chloro 1 butene, 3 chloro 1 butyne
Hybridization and resonance
A double bonded carbon has 3 groups around
it (sp2 hybridization)
Two of the p orbitals combine with the s orbital to
form three sp2 hybrid orbitals.
The remaining p orbital is left unchanged and
lies perpendicular to the flat molecule.
The overlap of the p orbitals forms a pi bond.
Sigma bond is the direct overlap of hybrid
orbitals
http://www.mhhe.com/physsci/chemistry/a
nimations/chang_7e_esp/bom5s2_6.swf
Resonance is when several pi bonds lie
in the same plane and all overlap
A pattern of alternating single and double
bonds results in resonance.
Examples: 1,3 pentadiene, benzene
(1,3,5 cyclohexatriene)