Transcript Unit 8 – Organic Chemistry

Unit 8 – Organic Chemistry
Text – Ch. 1 and 2
Intro to Organic Chem
• Originally, Organic Chemistry was the chemistry of living
things.
• Chemists were aware of a very large number of organic
compounds (such as dyes, soaps, vinegars, sugars,
perfumes, gums, and rubber, to mention a few) but were
unable to explain how so many compounds could be
made from only a few elements.
• Swedish chemist Jöns Jakob Berzelius (1779–1848) had
just explained inorganic compounds as being formed by
oppositely charged atoms.
Intro to Organic Chem
• However, this did not explain organic
compounds such as C2H6, C2H4, C3H8, C4H10,
and so on.
• It was common knowledge that Cl2 could be
substituted for H in C2H6 to produce C2Cl6. This
meant, however, that a negative Cl could be
substituted for a positive H. This was not
consistent with Berzelius’s idea of oppositely
charged atoms attracting.
Intro to Organic Chem
• Up to this point, no organic compound had been
synthesized from inorganic materials and, as a
result, many scientists believed that organic
compounds were formed only under the
influence of a vital force.
• It was Friedrich Wöhler (1800–1882) who, in
1828, made a remarkable discovery at the
University of Göttingham in Germany. He
attempted to prepare ammonium cyanate by
means of a double decomposition reaction in a
solution of ammonium chloride and silver
cyanate.
Intro to Organic Chem
• Both of these compounds were considered to be
inorganic.
• Instead of producing ammonium cyanate,
however, he obtained crystals of urea, an
organic compound.
NH4Cl + AgCHO
AgCl + CH4N2O
Urea
Intro to Organic Chem
Therefore,
• Within a few years of this event, when acetic
acid and several other organic compounds had
been prepared from inorganic materials, the
validity of the vital force was questioned.
•
•
Organic Chemistry is
As time passed, more and more organic
associated
with
all
compounds
were synthesized
from inorganic
materials.
molecules that contain
It became obvious that it was not necessary for
all organic compounds
to be associated with
carbon
living organisms.
Chemistry of Carbon
• Carbon has four valence electrons
– Therefore, it can bond four times per carbon
– Single bonds, double bonds, triple bonds
Hydrocarbons
• Hydrocarbon
– Made of hydrogen and carbon
• Two classes of hydrocarbons
– Chains – Aliphatic and Cyclic hydrocarbons
– Rings – Aromatics
Hydrocarbons
• Alkanes
– Are saturated hydrocarbons
– All bonds are single and filled with hydrogen
– Names end in “ane”
– General formula is CnH2n+2
• Ex. Methane, Ethane, Propane
Hydrocarbons
• Alkenes
– Are unsaturated hydrocarbons
– Some bonds are single and filled with hydrogen, while
others are double bonds
– Names end in “ene”
– Give the position of the bond by using the smallest
numbers possible
– General formula is CnH2n
– More reactive than alkanes
• Ex. Ethene, Propene, Propadiene
Hydrocarbons
• Alkynes
– Are unsaturated hydrocarbons
– Some bonds are single and filled with hydrogen, while
others are triple bonds
– Names end in “yne”
– Give the position of the bond by using the smallest
numbers possible
– General formula is CnH2n-2
– More reactive than alkenes
• Ex. Ethyne, Propyne
Hydrocarbons
• Cyclic Hydrocarbons
– Hydrocarbons arranged in a ring
– Chain end loses one H, and forms a bond
– Name has “cyclo” in it
• Ex. Cyclohexane, cyclohexene
Hydrocarbons
• Aromatics
– Contain a benzene ring
– Called aromatic as most have distinctive odours
– If a functional group, it is called “phenyl” group
– Benzene
• Carcinogen, liquid (low mp and bp), insoluable in water, used to
make derivatives, flammable
• Examples – trinitrotolulene, napthalene, vanillin, salicylic
acid, 2-phenyl butane
– When you change the functional groups, you change the
structure
Hydrocarbons – functional groups
and isomers
• Isomers
– Two molecules which have the same formula but a
different structure
– Therefore they react differently
• For methane, ethane and propane, there are no
isomers or branches
• But butane, has two isomers
• Examples
Hydrocarbons – functional groups
and isomers
• Rules for Naming Isomers (branched
hydrocarbons)
– Find the longest chain of carbons
– Count from the end of the chain closest to the branch
or branches
– Name the longest branch(es) then the chain
– If the structure contains a double or triple bond, it
takes priority and is named and numbered from the
bond
– Goes in alphabetical order
– Examples
Hydrocarbons – functional groups
and isomers
• Functional Groups
– CH3- R
– CH3- CH2- R
– CH3- CH2- CH2- R
– OH- R
–R–O–R
– NH2 – R
methyl
ethyl
propyl
hydroxyl (alcohol)
ether
amyl (amine)
Hydrocarbons – functional groups
and isomers
• Some special ways to name are to look at the
functional groups and the point at which they are
bonded
–
–
–
–
n – normal (on the end)
iso – in the middle
s - secondary
t – tertiary
• Examples
– Isopropyl alcohol, t – butyl alcohol, 2 – butanol or s butanol
Hydrocarbons – functional groups
and isomers
• Functional Groups (Cont)
Carboxyl group
Aldehyde
Organic acids
Ketone
Amide
Ester – made from the condensation reaction
of an alcohol and an organic acid
Reactions of Alkanes, Alkenes and
Alkynes
• Alkanes
– Without energy, alkanes generally are inert
– When they are exposed to a spark, they form
carbon dioxide and water.
2 C4H10(g) + 13 O2(g) 8 CO2(g) + 10 H2O(g)
Reactions of Alkanes, Alkenes and
Alkynes
• Alkanes (continued)
– When exposed to steam and extreme
temperatures, alkanes break to form an
alkene and hydrogen gas
– This is called thermal cracking or
dehydrogenation and takes temperatures of
1400oC
Reactions of Alkanes, Alkenes and
Alkynes
• Alkanes (Cont)
– Going from alkenes to alkanes (or
hydrogenation) does not take as much energy
as dehydrogenation
– In presence of a catalyst and hydrogen, the
alkene adds the hydrogen at the carbons
surrounding the double bond
Reactions of Alkanes, Alkenes and
Alkynes
• Halogenation (Text p. 24 – 26)
– Alkanes that react with heat or uv light, will go
through a substitution reaction, where a alkyl
halide will be produced
– This is called a substitution reaction
– If the reaction proceeds, a di-substitution
reaction takes place
Reactions of Alkanes, Alkenes and
Alkynes
• Halogenation (p. 24 – 26)
– Alkenes and alkynes are unsaturated and
more reactive than alkanes
– Since no hydrogen is lost, this reaction is
called an addition reaction, and occurs at
room temperature
– Alkenes and alkynes will react with halogens,
as well as hydrogen halides and water
Reactions of Alkanes, Alkenes and
Alkynes
• Reactions – Markovnikov’s Rule (p. 26)
– When a reactant consists of non-identical
atoms (such as a hydrogen halide), and is
added to an alkene or alkyne, the hydrogen
atom bonds to the side of the double bond
that has more hydrogen atoms
More Organic Reactions
• Aromatic Reactions (p. 28 and 29)
– Not very reactive
– Even though aromatics are unsaturated, they
undergo substitution reactions, to form
substituted benzene’s
More Organic Reactions
• Alcohols
– Contain a hydroxyl group, which is in the
place of a hydrogen group
– Where the hydroxyl group is will determine
the name (as mentioned before)
– Made from the hydration reaction of an alkene
and water
– A condensation reaction of two alcohols will
make an ether
More Organic Reactions
• Carboxylic Acids (Organic Acids)
– Weak acids that have a vinegar type smell, which can
be used in law inforcement
– Contain a carboxyl group that replaces the hydrogen
on the terminal carbon
– Take the name of the molecule with “oic” in the name
– Made from the oxidation of alcohols to aldyhydes and
then to acids
– Relatively soluable in water with high bp
– Used to make Esters
More Organic Reactions
• Esters (Organic “Salts”) (p. 64 – 67)
– Account for many smells we are accustomed to
– Made from the reaction of a carboxylic acid and
alcohol, which produces water (Condensation
reaction) and can be broken apart by hydrolysis
reactions
– The name is the alcohol, dropping the “ol” and adding
“yl” and the acid, dropping the “oic” and adding “oate”
– Really cool!!!
Polymers
• Post a WIKI!!!