Problem Set Assignments/2009 May 12 class: Chapt 1

Problem Set Assignments/2009  May 12 class: Chapt 1

Problem Set Assignments/2009 May 12 class: Chapt 1 #1,2; Chapt 2#6,8,18; Chapt 3 #3; Chapt 5 #26,30; Chapt 9# 1,14; Chapt 12#1,18 May 14 class: Chapt 6 #1,8; Chapt 8#1,21 Answers posted on the course website What will be on quizzes and exam? Lecture material and PP slides

Problem set material Explanations etc. from Demos Material covered in Whats in the News Questions: T/F; short answer and multiple choice format 6. Organic Chemistry : an overview carbon to candles chapter 6 All life depends on water and compounds of carbon Organic chemicals are those compounds containing carbon(at least 1 atom). Originally organic compounds were thought to be

only from living matter, ie. containing a vital force. ( consider the symbolism of organic foods) Probably ~10 million organic compounds known! Inorganic compounds are compounds/molecules that do not contain carbon. HYDROCARBON COVALENT BONDING H H H C

C H Hydrogen Atom H Carbon Atom Carbon with Hydrogen C:C C C

single C::C Carbon with Carbon C C double

C C triple ORGANIC STRUCTURES ( a short hand) HHH H-C-C-C-H H H H-C-H H CH3 CH2 CH2 or

CH3 or CH3CH2CH2CH3 or all Hs understood T h e P r o b le m w ith P r e fix e s C 5H C H 3

C H 2 C H 2 C H 2 12

C H 3 Is o m e r s ( p o s itio n a l) C H 3 C H C H P e n ta n e C H

2 C H 3 3 Is o p e n ta n e (M e th y l b u ta n e ) C H 3

C H 3 C C H C H3 3 N e o p e n ta n e ( D im e th y l p ro p a n e ) Positional Isomers of the Alkanes

# of Cs Formula 1 2 3 4 5 6 7 8 9 10 15

20 CH4 C 2H 6 C 3H 8 C4H10 C5H12 C6H14 C7H16 C8H18 C9H20 C10H22 C H # of Isomers

1 1 1 2 3 5 9 18 The International Union of Pure and Applied Chemistry, beginning in 1892, has attempted to systematize the naming of organic compounds. This IUPAC system for organic nomenclature is still in general use. Here are a few basic rules:

1. Find the longest continuous chain of carbon atoms and apply the appropriate term; this will be the parent name. # of Cs 1 2 3 4 5 6 7 8 9

10 Parent name methethpropbutpent* hexheptoctnondec- Derivation methe-(Gr.) aither(Gr.) protos + pion(Gr.) butyrum(Lat.) pente(Gr.) hex(Gr.) hepta(Gr.) okto(Gr.); octa(Lat.) novem(Lat.)

deka(Gr.); decem(Lat.) *NB. no sex- (Lat.) The First 10 Straight - Chain Alkanes Name Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane

Decane Molecular Formula CH4 CH3CH3 CH3-CH2-CH3 CH3CH2-CH2-CH3 CH3-CH2-CH2-CH2-CH3 CH3-CH2-CH2-CH2-CH2-CH3 CH3-CH2-CH2-CH2-CH2-CH2-CH3 CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3 CH3CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3 CH3-CH2CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3 More than 10 Cs in the chain

Undecane (11), dodecane (12) tridecane(13),tetradecane(14), pentadecane(15) hexadecane (16) heptadecane (17), octadecane (18), nonadecane(19) After C19, beyond the scope of CHEM 1003! C20H42 is eicosane Where to start numbering? At the end of the chain with the most branches 3-methylhexane Families of compounds are compounds of similar

structure and therefore similar properties. Hydrocarbons are composed exclusively of carbon and hydrogen. There are 4 sub-categories of hydrocarbons: alkanes alkenes alkynes aromatics Origin of Hydrocarbons H y d r o c a r b o n s (A lk y l) S tru c tu re

B ond S u ffix E x a m p le s C C S in g le ___ane

B u ta n e , is o o c ta n e C C D o u b le ___ene P o ly s ty r e n e , p r o p y le n e , -c a ro te n e

C C T r ip le ___yne A c e ty le n e (e th y n e ) Additional Complications! Isomers! Isomers are compounds that have the same

molecular formula but are different in some aspect of their structure, eg. a. positional: structural chemical b. geometrical: iso-, neo-, tert- -OH & C=O vs. -COOH cis-, trans- c. 3-dimensional(stereo-): all chiral centers mirror images (D/L; +/-) only 1 center

epimers 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 Non-superimposable Mirror images

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 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

Isomers with multiple (n) unique chiral centres # of isomers possible =2n. These are diastereomers: have different mp, bp Cholesterol has 8 chiral centres, hence 2 8= 256 possible isomers. But only one occurs naturally! Cholesterol : A steroid 8 chiral centres Geometrical isomers Simplest examples are cis-trans isomers

Differ only in the spatial arrangement of atoms Trans fats geometrical isomers of cis fats (cis=same) , trans= opposite 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 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) Organic Nomenclature - Descriptors R C R Examples C

C R trans C cis R R R ortho-

R R meta- R para= cyclo R cis- or transfatty acids PABA = paraamino benzoic

acid (in sunscreen) hexane cyclo butane pentane 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 A functional group is a small set of atoms, held

together by covalent bonds in a specific and characteristic arrangement, that is responsible for the principal chemical and physical properties of that compound Organic Functional Groups Functnl Grp Generic Suffix Prefix halocarbon -halide RX R

alcohol OH R OR -ol Examples halo- PVC, perchloroethylene hydroxy

menthol, ethanol cholesterol ether -ether alkoxy Methyl-tbutyl ether (MTBE); octane enhancer amine nicotine am(ine) amino- adrenaline cocaine Organic Functional Groups Functnl Grp

Generic R C = O aldehyde H RC=O R ketone Suffix Prefix Examples -al acyl

citronellal retinal formaldehyde -one ----- cortisone acetone testosterone 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 OR (acid + -oate R C = O amide

(acid+ NR2 -amide alcohol) ------ phthalates polyester ethyl acetate amido-

DEET Common Names vs. IUPAC Acetone (common solvent) is propanone Acetic acid (in vinegar) is ethanoic acid Benzene (potent carcinogen) is 1,3,5cyclohexatriene Chloroform is trichloromethane 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

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 C=C at the C9 position of the chain 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!! Salted candles dont drip! Compare flame intensity 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

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 Visible light Red is longest wavelength, violet is shortest 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!

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