Transcript Hydrocarbons - Haiku for Ignatius

Nomenclature Part III
Hydrocarbons and Other
Organic Molecules
Organic Chemistry
Organic Chemistry is the study of
carbon chain-containing compounds.
Carbon has special bonding abilities
that allow it to bond with itself to form
long chains, rings, tubes, and even
spheres!
Understanding Carbon Chemistry is
essential for anyone considering the
medical or pharmaceutical fields.
Hydrocarbons
Hydrocarbons are compounds composed
of carbon and hydrogen.
When the carbon-carbon chain contains
only single bonds, the hydrocarbon is said
to be Saturated.
Each carbon is “full” of hydrogens.
A carbon is “full” when it has 4 single bonds.
When double or triple bonding occurs in
the carbon-carbon chain, the hydrocarbon
is Unsaturated.
The double and triple bonds can break and
hydrogens can be added.
The Forms of Hydrocarbons
We will focus on three
Straight-Chain – all the carbons are in a
straight line.
2. Branched-Chain – the carbon chain is not in
a straight line, but has one or more branches.
3. Rings – the carbon chain forms a ring. The 6carbon ring with alternating double and single
bonds (benzene) is a very important chemical
because of its strong structure. It has many
applications.
1.
There are also two other types…
Tubes
Spheres
Alkanes
An alkane is a saturated hydrocarbon.
Alkanes contain ONLY carbon and
hydrogen.
Alkanes contain ONLY single bonds.
Alkanes can be either straight chains,
or branched chains.
The generic formula for an alkane is
CnH2n+2.
You should know the 1st 10…
1. CH4
Methane
6. C6H14
Hexane
2. C2H6
Ethane
7. C7H16
Heptane
3. C3H8
Propane
8. C8H18
Octane
4. C4H10
Butane
9. C9H20
Nonane
5. C5H12
Pentane
10. C10H22
Decane
Structural Isomerism
Structural Isomerism is when two
molecules have the same chemical
formula, but different structural geometry.
Alkanes made of branched carbon chains are
structural isomers of the straight chained
hydrocarbons.
The “branches” on branched chains are
called Substituents.
REMEMBER! The chain is always named for the
largest number of consecutive carbons. The longest
number of consecutive carbons may not be the straight
chain as it is drawn on the paper. Always count the
carbons from every angle to find the root name.
Structural Isomers of Butane
C4H10
Butane
2-methylpropane
n-butane
isobutane
Knowing how to name Organic Molecules is
IMPORTANT because…
1. There are two molecules with the formula C4H10.
2. Due to their very different shapes, they have very
different chemical properties.
3. We cannot identify them by formula alone.
4. Drawing them to identify them is inconvenient,
especially when typing.
5. There are far too many organic molecules to
name each one individually and be familiar
enough with all of them to communicate.
 So we came up with a set of rules where the
name tells you the shape of the molecule and
where stuff goes on it.
i <3 O-Chem!!!
Substituents
Substituents are “things” attached to a
carbon chain that are not hydrogen.
Substituents can be…
1. Carbon
chains that are smaller than the
main chain
2. Halogens
3. Organic Subgroups
We will learn how to name all 3!!
The Root name of a Hydrocarbon
The root name of a hydrocarbon is
always determined by the longest
continuous carbon chain.
If the longest chain contains 6 carbons
for example, the root name is hexane.
If the longest chain only contains 3
carbons, the root name is butane.
The root name of a hydrocarbon is
always the LAST part of the name.
Naming the Substituents
Substituents on the main carbon chain are
named using numbers and prefixes.
The number comes first, indicating which
carbon in the chain the substituent is on.
The carbon chain should be numbered in such a way
that the substituents are on the lowest numbered
carbons.
The number is followed by a hyphen.
The substituent is then represented by its
prefix. (common prefixes on next 2 slides)
If there are more than one substituent on a
chain, they are listed in alphabetical order,
each one followed by a hyphen.
For example, 3-ethyl-2-methylhexane
The order does not reflect the physical order on the
chain.
Some Common Substituent Prefixes
Smaller Alkane Substituents on a larger chain
are named by using the root and replacing –
ane with -yl.
Methane  MethylEthane  EthylPropane  PropylHexane  Hexyl-
Halogen Substituents are named by replacing
–ine with –o.
Chlorine  cloroFluorine  FluoroBromine  BromoIodine  Iodo-
Other Common Substituents
-OH  Hydroxyl-NH2  Amino-
Important Akyl Substituents
Carbon Chains with Multiple
Copies of the Same Substituent.
If there are 2 or more of the same
substituent on the chain they can be
combined using the Latin prefixes (mono,
di, tri, tetra, etc…)
For example, 2,4-dimethyldecane, indicates that there
is an methyl group on both carbon #2 and carbon #4
The carbon numbers are listed in numerical
order and separated by comas.
A hyphen follows the last number.
The prefix is added to the beginning of the
substituent’s prefix.
Name the Isomers of Butane, Pentane,
& Hexane using the formal rules…
Hydrocarbons that form LOOPS!
Cyclic Hydrocarbons occur when the
hydrocarbon chain forms a ring.
There must be at least 3 carbons to make a
ring, because 2 carbons can only be linear. ;)
Cyclic Hydrocarbons have the generic
formula CnH2n.
Naming Cyclic Hydrocarbons
They follow the rules for naming alkanes, but
the prefix cyclo- is added to the root name.
Example: a 6-carbon ring is called
cyclohexane.
The First 4 Cyclic Hydrocarbons
Cyclic Hydrocarbon Geometry
The first two cyclic hydrocarbons (cyclopropane &
cyclobutane) have a strained geometry because
the bond angles are so much smaller than that of
a tetrahedral carbon.
For this reason they are very reactive compared to linear
alkanes.
Cyclopentane and Cyclohexane have a stable
geometry because the bond angles are very close
to that of tetrahedral carbon.
This stability lowers the reactivity of these two.
Cyclic hydrocarbons greater than hexane loose
this stability because the bond angles once again
become strained, as they deviate from that of
tetrahedral carbon.
Like the smaller rings, these too are very reactive.
Unsaturated Hydrocarbons
Unsaturated Hydrocarbons contain either a
carbon-carbon double bond, or a carboncarbon triple bond.
These molecules have special properties
because they involve pi bonds, which do
not allow the freedom of rotation that
saturated hydrocarbon chains, which
contain only sigma bonds, have.
There are two types, Alkenes & Alkynes.
Alkenes
Alkenes are unsaturated hydrocarbon chains
that contain one or more double bonds.
Alkenes have the generic formula CnH2n
Naming Alkenes
Alkenes are named using the same roots as the
alkanes, but the –ane is changed to –ene.
The lowest numbered carbon involved in the
double bond is represented by that number
followed by a hyphen attached to the beginning
of the root.
Example: H3C-CH=CH-CH2-CH3 is called 2-pentene
If there is more than one, the Latin prefixes are
used, but this time it goes in front of the –ene.
Example: H3C-CH=CH-CH=CH-CH3 is called 2,4hexadiene
Alkynes
Alkynes are unsaturated hydrocarbon chains
that contain one or more triple bonds.
Alkynes have the generic formula CnH2n-2
Naming Alkynes
Alkenes are named using the same rules as the
alkenes, but the –ene is changed to –yne.
The triple bond in Alkynes means that this
part of a hydrocarbon chain is always linear
in its geometry.
The geometry of Alkenes is not as simple,
and must be discussed further…
Cis-Trans Isomerism
The restricted rotation around a double
bond leads alkenes to have a property
called Cis-Trans Isomerism.
When substituents are located one on each
carbon of the double bond, they can exist
either both on the same side of the bond,
or on opposite sides.
A Cis- Isomer occurs when both substituents
are on the same side of the bond.
A Trans- Isomer occurs when each substituent is
on a different side of the bond.
Remember there must be substituents on
each carbon in the bond for this to occur.
Naming Cis-Trans Isomers
Cis-Trans Isomers are named as other
alkenes with one addition…
The cis- or trans- prefix is added before
the number indicating the first carbon in the
double bond.
Aromatic Hydrocarbons
Aromatic Molecules are a special
group of unsaturated hydrocarbons.
So named due to the notable smell that
all aromatic molecules seem to have…
Benzene is the simplest example.
C6H6
Benzene’s Structure is
more accurately
represented like this 
Research has revealed that the bonds in a
benzene ring are actually all equivalent
The double-single bonds exist in
resonance, and are more like a hybrid, or a
combination of a double and single bond.
The structure is incredibly stable, and is
very important in organic reactions.
Benzene is also a very important solvent
for non-polar chemicals (benzene is to
organics as water is to salts).
Benzene and Substituents
Benzene can hold substituents by
substituting “things” for hydrogens just
like other hydrocarbons.
When there is only one substituent,
benzene is named with the
substituent prefix.
Examples are chlorobenzene and
methylbenzene.
When there are two substituents,
however there are more rules. :D
2 Substituents on Benzene
If the same, the Latin prefixes are used
If different they are listed alphabetically
They can be arranged in 3 ways…
1.
On adjacent carbons
“Ortho” – represent by oo-dibromobenzene
2.
With one carbon in between
“Meta” – represented by mm-bromomethylbenzene
3.
On opposite carbons
“Para” – represented by pp-bromochlorobenzene
Benzene as a Substituent
Benzene does not make the best
substituent because it is so BIG.
Big molecules take up a lot of space,
and don’t fit easily on carbon chains,
but it happens.
Benzene has the prefix phenyl- when
it is used as a substituent.
Some Common
Aromatic Hydrocarbons
The Organic Subgroup
Some Organic Molecules contain atoms
other than carbon and hydrogen.
We have already seen examples of this with the
halogen substituents.
Most of the time, these “other” atoms appear in
repeating patterns that are easy to recognize,
called organic subgroups.
Organic Subgroups are also called
Functional Groups.
This is because each organic subgroup has its
own characteristic chemical behaviors.
Some Chemical Shorthand
The following are symbols used to
represent (generically) groups of chemicals
that behave similarly.
Review…used to describe the ions in salts.
M+ = metal cation
X- = nonmetal anion
New…These you must know to understand
Organic Subgroups.
X = halogen
R = hydrocarbon
R’ = hydrocarbon different from R
R’’ = hydrocarbon different from R & R’
The Common Functional Groups
Class
Functional Group
Generic Formula
Halohydrocarbon
-X
-OH
-O-CŐH
-CŐ-CŐOH
-CŐO-NH2
-CŐNH-
R-X
R-OH
R-O-R’
R-CŐH
R-CŐ-R’
R-CŐOH
R-CŐO-R’
R-NH2
R-CŐNH-R’
Alcohol
Ether
Aldehyde
Ketone
Carboxylic Acid
Ester
Amine
Amide
Functional Groups 2D with Lewis Dot
(better representation of the shape)
Alcohols
Alcohols are classified by the presence of a
hydroxyl group (-OH).
Alcohols are named by giving the carbon
number the hydroxyl group is on, followed
by a hyphen. Next comes the root name,
replacing the ending -e with –ol.
Examples:
CH3OH is methanol
CH3CH2CH2OH is 1-propanol
CH3CHOHCH3 is 2-propanol
Classifying Alcohols
Alcohols are classified based on the number
of hydrocarbons bonded to the carbon where
the hydroxyl group is located.
# of ‘R’
Groups
1
Generic
Formula
R-CH2-OH
Classification
2
R-(R’)CH-OH
Secondary
3
R-(R’)(R”)-C-OH
Tertiary
Primary