Problem Set Assignments

1
Problem Set Assignments

• Jan 9 class Chapt 1 1,2 Chapt 26,8,18 Chapt
  3 3 Chapt 5 26,30 Chapt 9 1,14 Chapt
  121,18
• Jan 13 class Chapt 6 1,8 Chapt 81,21
• Answers posted on the course website

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What will be on quizzes and exam?

• Lecture material and PP slides
• Problem set material
• Explanations etc. from Demos
• Material covered in weekly Whats in the News
• Questions T/F short answer and multiple choice
  format

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Question from Day 1

• Q Despite having the symbol K derived from the
  Latin (Kalium meaning alkali) or Arabic qali
  (alkali) why do we call this element Potassium
  and not Kalium??
• Also since we use the symbol Na derived from the
  Latin (Natrium), why do we call this element
  Sodium and not Natrium?

4
A Early Soap Making

• Wood ashes (contain both sodium carbonate and
  potassium carbonate) were treated with cold water
  and concentrated by boiling in a pot, to produce
  potash Due to much higher solubility of the
  potassium salt, this is an effective separation.
• Then potash was mixed with animal fat to make
  soap.
• Until 1807, no distinction was made between
  sodium and potassium!

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Sir Humphry Davy 1778-1829

• Discovered anesthetic properties of Nitrous oxide
  (N2O laughing gas) and was addicted to it. Also
  a pioneer in electrolysis.

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Sir Humphry Davy

• Science is a wonderful thing provided you dont
  have to make a living at it!
• Michael Faraday was his famous student
• Used the first battery invented by the Italian
  Volta in 1800 to carry out electrolysis reactions
• Purified 6 new alkali metals. Na, K (1807) and
• Mg, Ca, Sr and Ba in 1808.

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1807 electrochemical isolation of Na and K

• Davy used electrolysis of dry molten caustic
  potash (later detd to be KOH) to get pure
  potassium, and NaOH to get pure Na.
• A number of other compounds containing potassium
  have potash in their traditional names ie.
• Potash fertilizer (K2O) carbonate of potash
  (K2CO3) saltpeter KNO3.

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Washing soda and baking soda

• These are sodium carbonate and sodium bicarbonate
  respectively. Since both contain Na, this element
  was called sodium by the English
• NB.Baking powder contains baking soda , but also
  cream of tartar, so not interchangeable in the
  kitchen!...............
• Early German recipes for gingerbread used potash!

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Potash Canadian Connections

• Early NA settlers burned stumps from land
  clearing to produce potash
• Saskatchewan has some of the worlds largest
  natural potash resources and Potash Corporation
  of Saskatchewan is worlds largest producer.
• Used in glass manufacture as well as a fertilizer

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6. Organic Chemistry an
overview carbon to candles chapter 6
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HYDROCARBON COVALENT BONDING
H H C H H
H




C




Hydrogen Atom
Carbon Atom
Carbon with Hydrogen


C C
C C


Carbon with Carbon
C C
C C
C C
triple
single
double
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ORGANIC STRUCTURES ( a short hand)
H H H H-C-C-C-H
CH3 CH2 CH2
or
CH3
H H H-C-H
H
or
CH3CH2CH2CH3
or
all Hs understood
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Positional Isomers of the Alkanes
of Cs Formula
of Isomers
1 2 3 4 5 6 7 8 9 101520
CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18
C9H20 C10H22 C15H32 C20H42
1 1 1
2 3 5
9 18
35 75
4347 366,319
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The First 10 Straight - Chain Alkanes
Name Molecular Formula
Methane Ethane Propane Butane Pentane Hexane
Heptane Octane Nonane Decane
CH4
CH3CH3

CH3-CH2-CH3
CH3-CH2-CH2-CH3
CH3-CH2-CH2-CH2-CH3
CH3-CH2-CH2-CH2-CH2-CH
3
CH3-CH2-CH2-CH2-CH2-CH2-CH3
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
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More than 10 Cs in the chain

• Undecane (11), dodecane (12) tridecane(13),tetrade
  cane(14), pentadecane(15) hexadecane (16)
  heptadecane (17), octadecane (18), nonadecane(19)
• After C19, beyond the scope of CHEM 1003!
• C20H42 is eicosane

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Where to start numbering?

• At the end of the chain with the most branches
• 3-methylhexane

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Origin of Hydrocarbons
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Additional Complications!

• Isomers!

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Optical isomers

• Enantiomers contain one chiral (Gr. Chiros
  hand) center and are non-superimposable mirror
  images
• Are identical in all respects except for the
  direction in which they rotate plane polarized
  light
• D and L isomers
• Arise from tetrahedral C with 4 different
  substituents

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Non-superimposable Mirror images
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Amino Acids and Chirality

• All naturally occuring amino acids are the L
  isomers rotate the plane of polarized light in
  counterclockwise direction (Why??)
• Enzymes many are chiral and are only active for
  a specifically handed substrate
• Lock and key (hand in glove) mechanism for
  activity

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Drug activity and handedness

• L-Dopa is active vs. Parkinsons disease
• Its mirror image D-Dopa is inactive
• Chiral synthesis of pharmaceuticals is a
  multibillion operation
• Separations are costly and time consuming

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Isomers with multiple (n) unique chiral centres

• of isomers possible 2n.
• These are diastereomers have different mp, bp
• Cholesterol has 8 chiral centres, hence 28 256
  possible isomers. But only one occurs naturally!

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Cholesterol A steroid

• 8 chiral centres

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Geometrical Isomers

• Geometrical isomers
• Simplest examples are cis-trans isomers
• Differ only in the spatial arrangement of atoms

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Trans fats

• geometrical isomers of cis fats (cissame) ,
  trans opposite

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Trans fats

• Produced by partial hydrogenation of
  polyunsaturated vegetable oil
• Are solids-give longer shelf life to products
• Are worse than lard (satd fat) for your
  arteries!
• Banned in NYC as of Jan 1, 2008

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Can we totally rid our diet of trans fats?

• No, they occur naturally in small amounts in beef
  tallow, butter, milk
• Arise from microbial hydrogenation of
  polyunsaturated fats in the animals digestive
  system
• Ottawa City council has decided against a ban
  (wisely)

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Organic Nomenclature - Descriptors
Examples
R C C
C C R R
R
cis- or trans- fatty acids
trans
cis
R
PABA para-amino benzoic acid (in sunscreen)
R
R
R
R
R
ortho-
meta-
para-
hexane butane pentane

cyclo
cyclo
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More Complex Organic Molecules

• Contain atoms other than C and H
• To understand their properties, they are grouped
  according to the nature of these atoms and how
  they are bonded
• Classified according to reactivity and function,
  hence functional groups

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Organic Functional Groups
Functnl Grp Generic Suffix Prefix
Examples
halocarbon -halide halo- PVC,
R X R OH
R OR R NHR
perchloro- ethylene
alcohol -ol hydroxy menthol,
ethanol cholesterol
ether -ether alkoxy Methyl-t-butyl
ether (MTBE) octane enhancer
amine am(ine) amino- adrenaline
nicotine cocaine
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Organic Functional Groups
Functnl Grp Generic Suffix Prefix
Examples
R C O
aldehyde -al acyl citronellal
retinal formaldehyde
H
R C O
ketone -one ----- cortisone
acetone testosterone
R
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Organic Functional Groups
Functnl Grp Generic Suffix Prefix
Examples
R C O
carboxylic -oic carboxyl acetic acid
acid ASA
OH
fatty acids
R C O
ester -oate ------ phthalates
(acid
polyester
OR
alcohol) ethyl acetate
R C O
amide -amide amido- DEET
(acid
NR2
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Common Names vs. IUPAC

• Acetone (common solvent) is propanone
• Acetic acid (in vinegar) is ethanoic acid
• Benzene (potent carcinogen) is 1,3,5-cyclohexatrie
  ne
• Chloroform is trichloromethane

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Candle Chemistry

• Candle waxes are mixtures of solid saturated
  hydrocarbons (paraffins) and long chain (C16 or
  more) monoesters.
• Combustion in air generates CO2, H2O, heat and
  light

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Wax Components (esters)

• Oleo Stearin or Oleo Stearate (palm vegetable
  wax) mp 155-160oF
• Stearic acid is the common name for octadecanoic
  acid (C18)
• Oleic acid is same as stearic acid, except for a
  cis CC at the C9 position of the chain

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Dripless candles

• Made by overdipping a normal candle (wax mp.
  135-145 F) with a higher melting (160-170 F)
• Candle burns down the middle leaving a hallow
  rim/tube to hold the melted inner wax
• Or, try soaking a normal candle for 24 hours in
  salt water (2 tbs. salt to 2 cups water) for 24
  hours
• Demo!!

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Salted candles dont drip!

• Compare flame intensity

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Why does salt make a candle burn brighter?

• Wick absorbs the NaCl solution
• When the wax starts to burn, it excites the
  sodium electrons to a higher energy level
• Visible light (yellow) is given off when these
  electrons return to a lower E level
• Sodium D line at 589 nm (yellow) in visible range
  of 700 (red) to 400 (violet)3p to 3s

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Sodium D line

• Heat excites 2p electrons to 3p level
• Visible light (589 nm wavelength) is emitted when
  these electrons come down to the 3s level
• Recall electron configurations
• Na is 1s2, 2s2, 2p6, 3s1.
• Na has lost the 3s electron

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Visible light

• Red is longest wavelength, violet is shortest

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Why no drips?

• Flame is hotter and stronger with salt present in
  the wick, hence melted wax on top vaporizes and
  burns off before it drips down the side!