notes_ Lecture_Mar 10-11 2010.pdf

1 21.1 Alkanes: Saturated Hydrocarbons 21.2 Alkenes and Alkynes 21.3 Aromatic Hydrocarbons 21.4 Hydrocarbon Derivatives 21.5 Polymers 21.6 Natural Polymers ? Biochemistry Chapter 21. Organic and Biochemical Molecules Computer model of a globular protein ? Benzene, C6H6, is the prototype of aromatic compounds. An unsaturated cyclic hydrocarbon which is relatively less reactive compared to alkenes or alkynes. o r + + + C l 2 H N O 3 C H 3 C l C l N O 2 F e C l 3 H 2 S O 4 A l C l 3 + H C l + H C l C H 3 C h l o r o b e n z e n e N i t r o b e n z e n e T o l u e n e E . g . delocalized ? electrons - sp2 hybrid orbitals - Benzene undergoes Substitution Reactions - The products of these substitution reactions are monosubstituted benzene, with common names. - Systematic and common names with poly-substitution. 21.3 Aromatic Hydrocarbons 2 More Complex Aromatic Compounds ortho (o-) meta (m-) para (p-) X X X X X X 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 (o-)1,2 (m-) 1,3- (p-) 1,4- ? an organic semiconductor used in thin film transistors Some substituted benzenes and their names Pen tacenePentacene 21.4 Hydrocarbon Derivatives ? Functional Groups - Atoms or groups of atoms that are part of an organic molecule and that exhibit characteristic chemistry, e.g. reactivity towards a particular reagent. ( See common functional groups in Table 22.4) ? Alcohols - contain the hydroxyl (-OH) functional group. - nomenclature: replace the ?e of the parent hydrocarbon with ?ol. e.g. methane ? methanol, CH 3OH ethane ? ethanol, CH 3CH2OH In IUPAC naming, 1-Buten-2-ol OH is given a lower number CH2=CHCH2CH3 than C=C or halogen 1-Butene R C H 2 O H C H O H R R ' RCR ' R " O H H2C CHCH2CH3OH Primary alcohol (1o) Secondary alcohol (2o) Tertiary alcohol (3o) 3 - Aromatic alcohols phenol OH Example 21.6 6-Bromo-2-methyl-2-hexanol (a tertiary alcohol ) Name Type of alcohol - Hydrogen bonding is the main intermolecular interaction in alcohols R OH R O H HO R methanol bp = 65 ? CH3OH (molar mass=30) ethane bp = - 89 ? CH3CH3 (molar mass=30) vs R=alkyl or phenyl or other hydrocarbon substituent C C H 3 H 3 C O H C H 2 C H 2 C H 2 C H 2 B r1 2 3 4 5 6 4 Aldehydes and Ketones ? Both are characterized by the carbonyl group CO CHOR f o r m a l d e h y d eC HOH a c e t a l d e h y d eC HOH 3 C C o m m o n n a m e se . g . CR'OR ( a c e t o n e )2 - p r o p a n o n eC C H 3OH 3 Ce . g . ? Names: replace ?e with ?al for an aldehyde replace ?e with ?one for a ketone ? aldehyde carbon is always #1 in naming aliphatic compounds ? aldehydes ? Ketones Figure 21.13: Some common ketones and aldehydes R C H 2 O H R C H Oo x i d a t i o n p r i m a r y a l c o h o l a l d e h y d e R 1 C H O H R 2 R 1 C R 2 Oo x i d a t i o n s e c o n d a r y a l c o h o l k e t o n e ? Carboxylic Acids and Esters ? Carboxylic acids - Contain the carboxyl group: COOH - R-COOH ? carboxylic acid - Names: drop ?e add ?oic acid e.g. CH3COOH ethanoic acid ? parent ethan e - Synthesis: C H 3 C H 2 O H o x i d a t i o nK M n O 4 ( a g ) C H 3 C O O He t h a n o l a c e t i c a c i d( e t h a n o i c a c i d ) Fig. 21.14: Some Carboxylic acids 5 H 3 C CO O H + H - O C H 2 C H 3 H 3 C CO O C H 2 C H 3 + H 2 Oa c e t i c a c i d e t h a n o l e t h y l a c e t a t e - Names: alkyl prefix from the patent alcohol + replace ?oic of parent acid with -oateH 3 C C O O C H 2 C H 2 C H 2 C H 2 C H 2 C H 2 C H 2 C H 3 ( c o m m o n n a m e : n - o c t y l a c e t a t e ) n - o c t y l e t h a n o a t e C O H O O H + H O C C H 3 O C O H O O + C O C H 3 H 2 O S a l i c y c l i c a c i d A c e t i c a c i d A c e t y l s a l i c y c l i c a i c d a s p i r i n ? Esterification reaction R 1 CO O H + H - O R 2 R 1 CO O R 2 + H 2 Oa c i d a l c o h o l E s t e r ? Useful for the synthesis of polymers Esters ? contain the functional group ? synthesis: carboxylic acid + alcohol ? ester COO ? Amines ? Other Functional groups ( Not in Table 22.4) R 1 N H C O R 2 + H 2 OR 1 N H 2 + H O C O R 2 A m i d e s E . g . H 3 C CO N C H 2 C H 3 N - e t h y l a c e t a m i d e ( c o m m o n n a m e ) N H C O a m i d e g r o u p ( a l s o p e p t i d e b o n d ) H Table 21.6 Some common Amines R N H 2 R N HR ' R NR ' R " Primary amine (1o) Secondary amine (2o) Tertiary amine (3o) 6 21.5 Polymers ? A polymer is a large molecule ? ?poly? many ? ?mer? part ? also known as macromolecules ? polymers typically have molar mass in the range of 105 to 107 g/mol ? the enormous size of polymers has consequences for many physical and chemical properties ? rapidly become solids with good strength ? form unusual solutions (recall collegative properties of solutions) Greek ?polymer? = many parts Polymers Synthetic Elastomers (Rubbers) natural Plastics (Thermoplastics) Thermosetting ? adhesives ? superglue Proteins / polynucleotides Polysaccharides (sugars) Gums Polymerization ? A polymer-forming reaction is called polymerization Polymerization addition polymerization (chain-growth polymerization) ? addition polymers Condensation polymerization (step-growth polymerization) ? condensation polymers an example of a monomer ? A monomer is a molecule that can be polymerized to give a polymer. ? An addition polymerization consists of 3 different steps. i. initiation ii. propagation iii. termination free radical ionic etc. ? Addition Polymerization n CH2=CH2 n>> 103 ethylene catalyst C C H H H Hn polyethylene 7 ? Free radical polymerization of vinyl monomers ? Initiation CH2=CH2 + I · ? free radical initiator generated by various ways ? Propagation growing active chain ? Termination (i) (ii) (iii) I CH2CHH I C H 2 C H H + H 2 C C H 2 I C H 2 C H 2 C H 2 C H H I C H 2 C H 2 + H 2 C C H 2C H Hx I C H 2 C H 2 C H Hx + 1 I C H 2 C H 2 +CHHx CHH C H 2 C H 2 Iy I C H 2 C H 2 x + y + 1 I Table 21.7 Some Common Synthetic Polymers, Their Monomers, and Applications 8 Table 21.7 Some Common Synthetic Polymers, Their Monomers, and Applications (Continued) ? Condensation Polymerization (Step-Growth Polymerization) ? polymerization reactions involving the elimination of a small molecule, such as water or methanol, at each step. n HO-CH2CH2-OH (ethyl glycol, a dialcohol) + (terephthalic acid) esterification rxn Poly(ethylene terephthalate) (PET) mylar, dacron, etc. ? a polyester used for fibers for clothing, films for photography, etc. + (2n-1) H2O small molecules non-monomers ? cannot be polymerized monomers ? polymerizable ? Monomer ? a molecule capable of being polymerized into a high molecular weight polymer ? a monomer is bifunctional or multifunctional. i.e. has two or more functional groups suitable for polymerization Monofunctional (not a monomer) bifunctional(not a monomer) bifunctional( a monomer) C O O HH O O Cn CC OO O O C H 2 C H 2 n C O O H N O 2O 2 N H 2 N N H 2 9 ? Polyesters HO-R1-OH H2N-R2-NH2 HOOC-R3-COOH HO-R1-OH +HOOC-R 2-COOH + (2n-1) H2O end group end group ? Polyesters can also be made from a single monomer, e.g. self-condensation of ?-hydroxycarboxylic acids ? Self-condensation of aminoacids: HOOC-R-NH2 + (n-1) H2O polyamide R= ?CH 2? , nylon 65 ?R -NHCO? n H O R 1 O CO R 2 CO O Hn n HO-R-COOH + (n-1) H2OR COO n ? Polyamides + (2n-1) H2O Polyamide is nylon 66 (Du Pont) H 2N C H 2 N H 2+ H O O C C H 2 C O O H 6 4 n n H N C H 2 N H C O6 C H 2 CO n4 ? Polyimides high temperature dielectric films used in computer chips ? Polyurethanes ? biocompatible materials for implants, drug delivery, etc. ? Polymerization Processes ? 4 Main approaches are used industrially: ? bulk polymerization: only the monomer e.g. styrene, vinyl chloride, methyl methacrylate etc. ? Solution polymerization: monomer in a solvent e.g. polyethylene, poly(acrylonitrile), poly(vinyl acetate) ? Suspension polymerization: organic monomer dispersed in water ? emulsion polymerization: insoluble liquid monomer disperse in an aqueous phase with a surfactant e.g. poly(vinyl chloride) O O O O OO + H 2 N R N H 2 N N O O OO R n + ( 2 n - 1 ) H 2 O w h e n R = O O CO NH 10 ?- Conjugated Polymers: The 4th Generation of Polymers Recall Conjugated Molecules ? Have been around a long time with numberous examples from organic and biological chemistry (e.g. ?-carotene, 11 conjugated double bonds; chromophore responsible for color vision; etc.) ? Molecules composed of alternating single and double or triple bonds e.g. 1,3-butadiene 1,3,5-hexatriene benzene naphthalene anthracene pentacene biphenyl terphenylbenzene ?- Conjugated Polymers: polymer semiconductors trans-polyacetylene, trans-PA poly(p-phenylene), PPP polypyrrole, PPy poly(p-phenylene vinylene), PPV polyquinoline, PPQ n n S n N n n N n S S S S N N N N H H H H H N P h N P h N P h polythiophene, PT 11 N P h N P h N P h S S S S S R R R R R R ?-Conjugated Polymers Solar Cells, Photodetectors, Imaging technologies Chemical & Biosensors LEDs, Lasers Electrochromic Devices, Batteries Molecular Electronics Thin Film Transistors ? Photophysics ? Charge Transport ? Photoconductivity ? Conductivity ? Redox Properties ? Photophysics ? Luminescence ? Charge Transport ? Charge Transport ? Single-Molecule Charge Transport ? Electrochemistry ? Electronic Structure Pei-Tzu 22.5 Polymers