Transcript Organic Chemistry - WilsonSCH4U1-07-2015

Organic Chemistry
The Chemistry of Carbon
Intramolecular Forces
• Forces of electrostatic attraction within a
molecule.
• Occur between the nuclei of the atoms and their
electrons making up the molecule (i.e. covalent
bonds)
• Must be broken by chemical means and form
new substances when broken.
• Determine the chemical properties of a
substance.
Intermolecular Forces
• Forces of attraction between two molecules (i.e.
London dispersion forces, dipole–dipole
interactions or hydrogen bonds)
• Much weaker than Intramolecular forces and are
much easier to break.
• Physical changes (changes of state) break or
weaken these forces.
• Do not form new substances when broken.
• These forces determine the physical properties
of a substance.
London Dispersion Forces
• These forces are based on the simultaneous
attraction of the electrons of one molecule by the
positive nuclei of neighbouring molecules
• The strength of the force is directly related to the
number of electrons and protons in a given
molecule
• The greater the number of electrons and protons
the greater the force
Dipole-Dipole Forces
• Occur between polar molecules having dipoles.
• Molecules with dipoles are characterized by
oppositely charged ends that are due to an
unequal distribution of charge on the molecule.
• The polarity of a molecule is determined by both
the polarity of the bond and the shape of the
molecule.
• These forces are based on the simultaneous
attraction of the electrons of one dipole by the
dipoles of neighbouring molecules.
• The strength of the force is related to the polarity
of the given molecule.
Hydrogen Bonds
• These forces are a type of dipole – dipole
interaction.
• Occur between Hydrogen atoms in one
molecule and highly electronegative atoms (F,
O, N) in another.
• The strongest of the Intermolecular forces and
are about 1/10 the strength of a covalent bond.
Characteristics of Organic Compounds
1. Made of carbon atoms in chains or rings.
2. Contain covalent bonds.
3. Principle intermolecular force is London
Dispersion.
4. One molecular formula can represent many
different compounds (isomers).
5. Properties are determined by the presence of
certain groups within the compound (functional
groups).
Why are there so many Organic Compounds?
1. Carbon has 4 valence electrons therefore 4
bonds.
2. Carbon readily bonds with other carbon atoms
forming chains, branched or cyclic compounds.
3. Carbon also readily bonds with other elements
such as O, N, S, halogens.
General Naming Rules for Organics
• The prefix indicates the
number of carbon atoms
in the chain.

• The ending indicates
the functional groups in
the structure.
C=C “ene”
-OH “ol
# of C’s
1
2
prefix
meth
eth
3
4
5
6
prop
but
pent
hex
7
8
9
hept
oct
non
10
dec
Alkanes
•
•
All C-C single bonds
General Formula CnH2n+2, where “n” is the
number of carbon atoms in the chain.
Naming
1. Use the correct prefix to indicate the number of
carbons.
2. Ending is “ane”
Drawing Organic Compounds
There are 3 ways to draw an organic compound.
1. Structural Diagram: shows all bonds in the
molecule. (the H’s are generally left off to
keep structures clean)
2. Condensed Structure: no bonds but all atoms
are shown in sequence. (Must put bonds
between C’s in for cyclo’s)
3. Line (Skeletal) Diagram: carbon atoms are
implied by the vertices (including ends) in the
structure, H’s are not shown but any other
atoms are written.
Structural
Condensed
butane
CH3CH2CH2CH3
or
CH3(CH2)2CH3
propan-1-ol
CH3CH2CH2OH
or
HOCH2CH2CH3
methoxyethane
CH3OCH2CH3
Line
Naming Branched Hydrocarbons
1.
2.
3.
4.
5.
6.
Identify the longest continuous chain or ring of
carbon atoms.
Number the carbons from the end that gives the
lowest sum for the numbers of the branches.
Name each branch and indicate its location with a
number.
List the branches in alpha order before the prefix
for the number of carbons.
Commas separate numbers and hyphens
separate numbers from words.
If there is more than 1 of the same branch Greek
prefixes are used to indicate this but the prefix is
not counted in determining alpha order.
Common Branches
-Br
-Cl
-F
-I
-CH3
-CH2CH3
-OH
bromo
chloro
fluoro
iodo
methyl
ethyl
hydroxy
H3C
CH
isopropyl
H3C
H3C
H3C
tert-butyl
C
CH3
-NH2
-NO2
amino
nitro
Alkenes
• Contain 1 or more C=C double bond.
• When naming use the suffix “ene”.
• The position of the double bond is indicated for
simple alkenes with 4 or more carbons or for all
branched alkenes.
• The position of the double bond is indicated with
a number in front of the “ene”
Alkynes
• Contain at least 1 C≡C bond.
• When naming use the suffix “yne”.
• The position of the triple bond is indicated for
simple alkynes with 4 or more carbons or for all
branched alkynes.
• The position of the triple bond is indicated with a
number in front of the “yne”
Types of Isomers
•
•
1.
2.
3.
4.
Isomers are molecules with the same formula
but different structures.
There are different types of isomers
Structural: are in the same organic family
(i.e. 2 alkenes) but have a different
arrangement of the atoms.
Functional: same formula but are in different
organic families (i.e. an alcohol and ether)
Geometric: differ in the placement of groups
around a double bond. (“cis-trans” isomers)
Optical: mirror images of each other that
cannot be superimposed onto each other.
Geometric Isomers (“cis-trans”)
• Double bonds prevent the rotation of atoms
around the bond axis which creates 2 different
molecules.
• In the “cis” form of the molecule the groups
attached to the double bond are on the same side
of the double bond.
• In the “trans” form of the molecule the groups
are attached on different sides of the double
bond.
• Cis and trans goes with the bond NOT THE
GROUPS ATTACHED!!
General Rules for Naming Organic
Compounds
• the prefix indicates the number of carbon atoms.
• the ending indicates the functional groups in the
structure (C=C “ene”, –OH “ol”).
• any branches are indicated before the prefix for
the number of carbons in alphabetical order.
• below shows the order of different components
in the name
BRANCHES # of C’s BONDS FUNCTIONAL GROUPS
in alpha order
alpha alpha order
(“oic acid” always last)
Naming Cyclo’s
1. Find the longest continuous ring.
2. Add “cyclo” in front of the prefix for the
number of carbons. i.e. “cyclopent”
3. Number the ring to give you the lowest
sum of all the numbers. You can start
anywhere and go clockwise or counter
clockwise.
4. If there is only 1 thing on the ring, NO
NUMBER is used. (e.g.
methylcyclopentane not 1methylcyclopentane)
•
•
•
•
Naming Hydrocarbon (Alkyl) Branches
Not all alkyl branches will be attached to the
main chain at carbon 1.
When carbon 1 of the branch is attached to the
main chain the branch is named using the prefix
for the # of C’s with “yl” attached. (i.e. propyl,
pentyl)
When it is not attached at carbon 1, you must
indicate which carbon it is attached at as follows
propan-2-yl, pentan-3-yl
Aromatics
• the organic family which are
derivatives of benzene
• Benzene has the molecular
formula C6H6
• The structural formula of
benzene consists of a 6member carbon ring with 3
C=C double bonds.
H
C
H
H
C
C
C
C
C
H
H
H
The Structure of Benzene
• Benzene is a planar molecule
• The carbon-carbon bonds in benzene are all the
same length and energy which is evidence that
the bonds are not true double and single bonds
If the bonds are not true single and
double bonds what are they?
• The carbon-carbon bonds in benzene are all 139
pm which is intermediate between the length of
a C-C single bond and a C=C double bond
(double bonds are shorter).
• This indicates that the electrons that make up
the “double bonds” in benzene are actually
delocalized (i.e. shared) around all six carbon
atoms.
• This arrangement of the electrons is
indicated in the LINE DIAGRAM by placing
a circle in the centre of the 6-member ring.
• Alternatively, benzene can be represented
as below.
Naming Aromatics
Using benzene as the main chain.
1. Identify the groups attached and number
accordingly
2. For compounds with 2 groups attached, the
following prefixes may be used instead of the
numbers; 1,2 = ortho (o), 1,3 = meta (m) and 1,4
= para (p)
Cl
Cl
Cl
Cl
Cl
ortho-dichlorobenzene
meta-dichlorobenzene
Cl
para-dichlorobenzene
• When the benzene ring is not the main chain,
phenyl is used to indicate a benzene ring as a
branch.
Common Names for Aromatics
Alcohols
• contain the hydroxyl group (-OH)
• alcohols can be classified by the position of the
OH group
1. Primary
• the -OH is at the end of the chain
Ex. butan-1-ol CH3CH2CH2CH2OH
2. Secondary
• the -OH is attached to a C with one H
Ex. butan-2-ol CH3CH(OH)CH2CH3
3. Tertiary
• the -OH is attached to a C with no H’s
Ex. Methylpropan-2-ol C(CH3)3OH
Naming Alcohols
1. Determine the name of the main chain
containing the hydroxyl group.
2. Remove the ‘e’ on the end of the main chain
and add ‘ol’.
3. Indicate the number to which the -OH is
bonded to starting at 3 carbons using the same
rules as for a double or triple bond.
4. If there are multiple -OH groups indicate this
using the appropriate Greek prefix.
Ethers
• Contain the R-O-R’ functional group.
Naming
1. The longest carbon chain connected to the O is
the base name.
2. Add “oxy” to the end of the prefix for the other
carbon chain (e.g methoxy, propan-2-oxy).
3. Indicate the position of the ether linkage using
a number in front of the “oxy branch”.
Peroxides
• Contain the R-O-O-R’ functional group.
• Very unstable and break down spontaneously to
form the ether and oxygen gas.
Naming
1. list the “yl” forms of the hydrocarbon chains in
alpha order, followed by the word peroxide.
Aldehydes and Ketones
• Aldehydes and ketones both contain the
carbonyl group (C=O).
• In aldehydes, the carbonyl group is attached to
the end carbon.
• In ketones, the carbonyl group is attached to a
carbon that is not on the end.
• They are considered functional isomers of each
other.
propanal
propanone
Naming Aldehydes
1. Take the longest chain containing the carbonyl
group, remove the “e” and add “al” as the
ending.
2. The C=O is always carbon 1. (unless it is with a
carboxylic acid)
Naming Ketones
1. Take the longest chain containing the carbonyl
group, remove the “e” and add “one” as the
ending.
2. If necessary indicate the position of the
carbonyl using the lowest numerical coefficient.
3. Any substituents are numbered so the sum is
the lowest.
Carboxylic Acids
• Contain the carboxyl functional group
Naming
1. Identify the longest chain containing the carboxyl
group, remove the “e” and add “oic” acid.
2. The carboxyl group is always carbon 1.
Note: “oic acid” always goes last in the name
Esters
O
• Responsible for tastes and odours.
• Contain the ester linkage
R
C
R'
O
• Made from an alcohol and a carboxylic acid.
Naming
1. Use the “yl” form of the alcohol proceeded
with the “oate” form of the carboxylic acid.
i.e. “alkyl oate”
O
H3C
C
O
CH2CH3
methylpropanoate
O
CH3
CH
H3C
C
O
2-propylethanoate
(isopropylacetate)
CH3
Amines
• Contain the amino functional group
Types of Amines
1. Primary: Contain 1 carbon chain (2 H’s).
2. Secondary: Contain 2 carbon chains (1 H).
3. Tertiary: Contain 3 carbon chains (no H’s).
Naming Amines
1. Determine the longest carbon chain and use it
as the base name.
2. List the other alkyl chains on the N in alpha
order with “N” in front of each to indicate that
they are on the nitrogen and not the main
chain.
3. Remove the “e” from the base name and a
number to indicate where the amino is attached
and then add “amine”
NH
N
N-ethylpentan-2-amine
trans-N,N-dimethylhex-3-ene-3-amine
HO
Cl
5-chloro-N-ethyl-N-methylhexan-2-amine-3-ol
N
Amides
• Contain the amide linkage.
O
C
N
R
R
1
• Structurally similar to esters
• This linkage joins amino acids together to create
polypeptides.
Naming Amides
• The name has 2 parts.
Base Name:
1. The prefix for the number of carbons in the
chain containing the carbonyl.
2. Add amide to the end.
Before:
1. Indicate any groups attached the nitrogen
using N in place of a number.
O
O
NH
N-ethylhexanamide
N
N,N-dimethylbenzamide
O
N
Cl
trans-N-chloro-N-methylhex-2-enamide
Organic Reactions
Combustion
• All of the organic families will under go
combustion.
Complete Combustion
Organic + O2(g) CO2(g) + H2O (g)
Incomplete Combustion
Organic + O2(g) CO2(g) + H2O (g) + CO(g) + C(s)
Substitution
•
An atom or group on the chain is replaced by
another. (SWITCH!! 1 on 1 off)
Families that Participate in Substitution
1. Alkanes
• With: halogens
• Catalyst: UV light
• Products: haloalkane + hydrogen halide
2. Aromatics
A) With Halogens
catalyst: FeBr3 or AlCl3
products: halobenzene + hydrogen halide
B) With Alkyl Halide
catalyst: AlCl3
products: alkyl benzene + hydrogen halide
C) With Nitric Acid
catalyst: sulphuric acid
products: nitrobenzene + water
3. Alcohols
with: hydrogen halide
catalyst: ZnCl2 (Lucas Reagent)
products: alkyl halide + water
• This reaction is a qualitative test for the
different types of alcohols because the rate of
the reaction differs greatly for a primary,
secondary and tertiary alcohol due to the
solubility of the resulting alkyl halides
Tertiary Alcohol  turns cloudy immediately (the
alkyl halide is not soluble in water
and precipitates out)
Secondary Alcohol  turns cloudy after 5 minutes
Primary Alcohol  takes much longer than 5
minutes to turn cloudy
4. Ethers
with: 2 binary acids
catalyst: heat (Δ)
products: 2 alkyl halides + water
5. Preparing Amines (Ammonia)
with: alkyl halide
catalyst: none
products: amine + hydrogen halide
Addition Reactions
•
Adding groups (or atoms) to the chain by
breaking a pi bond.
1. Alkenes
A) With Hydrogen
catalyst: platinum (Pt)
product: alkane
B) With Halogens
catalyst: CCl4
product: haloalkane (2 halogen atoms)
C) With Hydrogen Halide **
catalyst: NA
product: haloalkane (1 halogen atom)
D) With Water **
catalyst: H2SO4 + 100 °C
product: alcohol
** these reactions follow Markovnikov’s Rule
where the H gets added to the C in the double
bond that started with the most H’s
Addition Reactions cont’d
2. Alkynes
with: same as alkenes but 2 moles of each to
fully saturate the triple bond.
3. Aldehydes and Ketones
with: Hydrogen (aka a reduction)
catalyst: Pt and 101 MPa
product: alcohol
aldehyde = primary alcohol
ketone = secondary alcohol
Elimination
•
Removal of 2 atoms/groups to form a double
bond.
1. Alcohols
catalyst: H2SO4 and 100 °C
products: alkene + water
2. Alkyl halides
with: hydroxide ion
product: alkene + water + halide ion
Oxidation
•
•
A loss of electrons by the carbon atom.
Oxidizing agents will usually result in a colour
change.
dichromate  chromium 3+
(orange)  (green)
permanganate  manganese (IV) oxide
(purple)  (brown)
1. Alkenes
oxidizing agent: KMnO4 OR K2Cr2O7
product: “diol” (each C in the double bond gets
an OH group)
2. Alcohols
oxidizing agent: KMnO4 OR K2Cr2O7
product: depends on type of alcohol
Primary Alcohol = aldehyde  carboxylic acid
Secondary Alcohol = ketone
Tertiary Alcohol = NO REACTION
3. Aldehydes
product: carboxylic acid
- Since ketones can not be oxidized, oxidation
reactions can be used as a qualitative test to
distinguish between an aldehyde and ketone.
Oxidizing Agents:
A) KMnO4: purple to brown in aldehyde, stays
purple in ketone.
B) K2Cr2O7: orange to green in aldehyde,
stays orange in ketone.
C) Fehling’s Solution (copper (II) solution): blue
to an orangish brown precipitate (i.e. copper
metal) in an aldehyde, stays blue in a ketone
D) Tollen’s Reagent (Silver ions in ammonia):
clear and colourless to a black precipitate with a
silver mirrored coating on the glassware in an
aldehyde, stays colourless in a ketone.
• Known as the silver mirror test.
Silver Mirror Videos
http://www.youtube.com/watch?v=Uo1zW-JImRk
http://www.youtube.com/watch?NR=1&feature=en
dscreen&v=hUX_cpFWNso
Homework
• Questions from package
Condensation Reactions
• Linking 2 molecules together by removing water.
• The “H” for the water comes from 1 molecule
and the “OH” comes from another.
1. Alcohols
A) with: another alcohol
catalyst: H2SO4 + 140 °C
products: ether + water
B) with: a carboxylic acid
catalyst: H2SO4 + heat
products: ester + water
2. Amines (1° and 2° only)
with: carboxylic acid
catalyst: H2SO4 + heat
products: amide + water
Hydrolysis Reactions
• Splitting apart of a molecule by adding water.
1. Esters
A) Reversible
with: water
catalyst: H2SO4 + heat
products: alcohol + carboxylic acid
B) Irreversible
with: water + base
products: alcohol + carboxylate ion + metal ion
2. Amides
with: water
catalyst: H2SO4 + heat
products: amine + carboxylic acid
Rxn. Questions
•
•
•
•
•
•
•
P. 26 # 1-2
P. 27 # 9-10
P. 31 # 6
P. 37 # 1-2
P. 39 # 4-6
P. 53 # 1
P. 45 # 3
P. 62 # 5-6
P. 55 # 1-10a) c) P. 72 # 7-9
P. 74 # 30-32,35,37-44,47
P. 121 # 38,63,65,71,72,74,103,108,117
Polymers
• Read the following sections
• 2.2 pg 116-127
• Make sure you know
1. What is a polymer?
2. What an addition polymer is and how it is formed.
3. What a condensation polymer is and how one is
formed.
4. Polymer cross-linking
5. Be able to put monomers together to form a
polymer and identify the monomer given the
polymer.
6. Pg 120 #13, 15-18, pg 121 353-62, pg 127 #1-6