Othman Alameen Online Education Website

1. Lecture 2:
Organic Chemistry:
Carbon Chemistry

2. Let’s review bonding & Lewis
Structures
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decompressor
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3. What is pencil lead made of if it isn't lead?
• Pencil lead is a mixture
of graphite and clay.
• Graphite is one form of
the element carbon.
• Other forms of carbon
are diamond - the
hardest naturally
occurring substance on
the earth, soot,
charcoal and coke.

4. What is pencil lead made of if it isn't lead?
• Pencils used to be made with lead, many
years ago. Lead is poisonous and so sucking
the end of your pencil could be quite
dangerous.
• We now use graphite and clay because it is
safer and because we can make pencils of
different hardness

5. Chemistry of Living Things
• Living things are a lot like laboratories…
• There’s some serious chemistry going on
inside.
• Your body is an incredibly complex chemical
machine taking in chemicals & food, and
causing countless reactions to occur every
second.
• Biochemistry is the study of substances &
processes occurring in all living organisms.

6. What are living things made of?

7. I’m made of what???
• Guess how many elements your
body is made up of?
• 25 elements make up all living
things
• About 97% of your body’s mass
is made of just 4 elements:
oxygen, carbon, hydrogen, &
nitrogen.
• Two other major elements are
phosphorous & sulfur.

8. Minor
Elements
• Of course, other elements
are also important, but
they’re often found in
small amounts.
• They may seem
insignificant, but they’re
not.
• For example, iron makes
up only 0.004% of your
body mass, but you can’t
live without it!

9. Major Compounds
• The human body also relies on
many compounds, especially
water & salt.
• The human body typically consists
of 60-65% water.
• In other words, 2/3 of your body
weight is water.
• Water is important because many
of our body’s chemical reactions
can only occur in solutions
containing water.
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10. Major Compounds
• Blood, sweat, urine…
all mostly water!
• Salt is also important because
of how it can separate into its
two ions: Na+
and Cl-
.
• Sodium ions regular the
amount of water in our cells,
while chlorine ions help our
body digest food.
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11. The most important element is…
Carbon
• If you take away the water, the rest of the human body
is 53% carbon.
• It may not be the most abundant element in living
things, but it certainly is the most important. At one
time, scientists thought that the chemical reactions that
took place inside of living things could not occur
outside of them.
• The carbon molecules were so complex, scientists
thought they must have been made in some unknown
way. They called these carbon compounds organic
compounds

12. The most important element is…
• The word “organic” has lot s
of meanings. Event ually,
scient ist s realized t hat t he
react ions occurring inside
t he body could occur
out side it as well.
• They also learned how
import ant carbon is in all
living t hings, because of it s
abilit y t o bond wit h ot her
at oms.

13. The most important element is…
• Not all subst ances made of
carbon are living. Diamonds
& graphit e are pure f orms
of carbon.
• Non-organic carbon
compounds, and compounds
wit hout carbon, are called
inorganic compounds.

14. What is organic
chemistry?
• We used to describe organic chemistry as the
chemistry of living things.
• Since the chemistry of living things is based
on carbon, the chemistry of carbon
compounds has come to be known as
organic chemistry.
• It now includes the study of carbon
compounds which are not found in living
things and so is an incredibly large branch of
modern chemistry.

15. Why is life based on the element
carbon?
• There are two important properties of carbon
that make it a suitable element to form the
compounds in living things:
• Firstly, carbon atoms can link together to
form stable chains of great length.

16. Why is life based on the element carbon?
• Car bon at oms bind
st r ongly t o each ot her
and f or m ver y large
molecules which are
built around t his
car bon ' backbone' .
• The covalent bond bet ween t wo car bon at oms is
st r ong so t hat t he backbones are stable. I n all
of t hese compounds simple sub-unit s called
monomer s ar e linked t oget her by condensat ion
r eact ions.

17. What makes carbon so special?
• I t has a “cent r al” r ole in all living or ganisms.
• I t has 4 valence elect rons.
• I t makes 4 covalent bonds.
• I t can bond wit h any
element ,
but really loves t o bond wit h ot her carbon
at oms and make long chains

19. Lots of ways to draw this…

20. 3 Types of Carbon Backbones

21. Carbon forms long chains
• One carbon chain may cont ain hundreds of carbon at oms.
• Unlike ot her element s, carbon at oms can bond t o each
ot her t o f orm very long chains.
• One carbon chain may cont ain hundreds of carbon at oms.
Not ice how t he CH2 unit s repeat .
• A very large carbon-based molecule made of repeat ing
unit s is called a polymer. Each unit of a polymer is called
a monomer.
• Polymers can be thousands of at oms long

22. Carbon forms Rings
• Carbon-based molecules also can be shaped like rings.
Most carbon rings cont ain 5 or 6 carbon at oms.
• One of t he most import ant carbon rings is benzene.
• I t has 6 carbons & 6 hydrogens , wit h alt ernat ing
double bonds.

23. Carbon forms Rings
• Many compounds ar e based on Benzene.
• They of t en have very st r ong smells or ar omas,
so t hey are called aromatic compounds.
• An example of one aromat ic compound is a
molecule called vanillin.
• Guess what t hat smells like!

24. •You have
probably
hear d lot s
of science
f ict ion
programs
on TV
t alking
about
human
beings as
' car bon-
based lif e
f orms' .

25. Prepare to be assimilated…

26. Silicon is similar to carbon. Why are
there no life forms based on silicon?
Silicon is unsuitable because, although it is a
valence IV element like carbon (4 electrons
to share),
BUT the silicon-silicon covalent bond is not
strong enough for it to form long stable
chains.
So, it can not form molecules of the
complexity needed to make up cells like
carbon can!

27. We are not silicon based
life forms!

28. Long Chain Hydrocarbons & their
Names
• The alkanes make up a series of saturated
hydrocarbons, called an homologous series
because they have similar properties and have
the same general formula:
• The first four members of the series are
gases at room temperature and are called:
• methane, CH4
• ethane, C2H6
• propane, C3H8
• butane, C4H10

29. Covalent Bonding Review
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30. Alkanes

31. • Alkanes with increasing numbers of
carbon atoms have names are based on
the Greek word for the number of
carbon atoms in the chain of each
molecule.
• So you can get, for example,
• pentane (5),
• hexane (6),
• heptane (7)
• and octane (8).

32. • From pentane onwards, approximately
the next thirty alkanes in the series
are liquids.
• Alkanes with even longer chains are
waxy solids.
• They are typical covalent compounds,
insoluble in water but able to mix with
each other.
• Alkanes burn in oxygen to produce
carbon dioxide and steam.

33. Lots of carbon compounds seem to be
isomers. What is an isomer?
• In organic chemistry, there are many
examples of different compounds which
have the same molecular formula as
each other,
• But different arrangements
(structures) of the atoms in their
molecules.
• These are called isomers.

34. What is an isomer?
• These compounds are
said to be isomers of
one another.
• Isomerism also occurs
in inorganic
chemistry, but it is
less common.

35. If isomers have the same atoms in them,
surely they have the same properties, so
what's the point?
• In fact, these small changes in structure can
have significant effects on the properties of the
substance!
• But, it is important to realize that this can
have significant effects in a living system.
• One optical isomer of glucose, for example,
can be used by a living cell, but the other
isomer cannot.
• This is because the enzyme in the cell which
recognizes glucose is sensitive to only one
form.

36. There are two types of isomerism
common in organic chemistry:
1. structural isomerism
• Which have the atoms of their
molecules linked in a different
order.
• This can come about in one of
three ways:

37. Chain Isomerism
• Chain isomers of t he same compound ar e ver y
similar .
• Ther e may be small dif f er ence in physical
pr opert ies such as melt ing or boiling point
due t o dif f er ent st r engt hs of int er molecular
bonding.
• Their chemist r y is likely t o be ident ical.

38. Positional Isomers
• Positional isomers are also usually similar.
• Ther e ar e slight physical dif f er ences, but t he
chemical pr oper t ies are usually very similar.
• However, occasionally, posit ional isomers can
have quit e dif f er ent proper t ies

39. Positional Isomers
• A simple example of isomerismis given by propanol:
• it has t he f ormula C3H8O (or C3H7OH) and t wo isomers
propan-1-ol (n-propyl alcohol; I) and propan-2-ol (isopropyl
alcohol; II)
• Not e t hat t he posit ion of t he oxygen at om dif f ers
bet ween t he t wo: it is at t ached t o an end carbon in t he
f irst isomer, and t o t he cent er carbon in t he second.
• The number of possible isomers increases rapidly as t he
number of at oms increases; f or example t he next largest
alcohol, named but anol (C4H10O), has f our dif f erent
st ruct ural isomers.

40. Functional Group Isomers
• Functional group isomers are likely t o be
bot h physically and chemically dissimilar.

41. You Try
It!

42. How
did
you
do?