Welcome to 2014 hemistry S Enrichment Day osted by Department of hemistry and Biomolecular Sciences http://www.cbms.mq.edu.au No 1
2014 EMISTRY S ENRIMENT LETURE Production of Materials Ethene, Polymers and Ethanol For these lecture notes See www.cbms.mq.edu.au/hsc_enrichment No 2
I like chemistry a lot 1. True 2. False 0% 0% 1. 2. No 3
The Various Ways of Representing Ethene (Ethylene) See S Booklet from page 1 2 2 2 2 2 4 No 4
Alkenes as Valuable Building Blocks Ethene and other alkenes are essential building blocks for making important compounds Solvents (eg ethanol) Polymers (eg polyethylene, polystyrene, polyvinyl chloride) But does not occur naturally in great amounts No 5
Synthesis of Ethene from Ethanol Ethanol onc. 2 S 4 (at.) Ethene 2 This reaction involves a loss of water ( 2 ) = Dehydration Reaction No 6
Industrial Synthesis of Ethene Industrially, ethene (and other alkenes) produced from fractions obtained by the distillation of crude oil/petroleum The various fractions contain long-chained alkanes and alkenes Broken down into small molecules, including alkenes such as ethene, in a process known as cracking Thermal cracking and catalytic cracking (occurs at lower temperatures using zeolites - aluminosilicates) atalytic cracking has been examined in past exams e.g. see 2008 Q16, 2012 Q26, 2013 Q8 No 7
Which equation best represents catalytic cracking of a petroleum fraction? (modified from 2001 S Q3) 1. 16 34 (l) zeolite 16 34 (s) 2. n 2 4 (g) 2 2 n (s) 3. 4. zeolite 16 34 (l) 7 16 (s) + 3 2 4 (g) + 3 6 (g) zeolite 7 16 (s) + 3 2 4 (g) + 3 6 (g) 16 34 (l) 0% 0% 0% 0% 1. 2. 3. 4. No 8
Major Reaction Type of Alkenes Addition reaction: X Y X Y addition product No 9
Representative Alkene X-Y Addition Product Reaction Type ( 2 ) (with Ni catalyst) l (l) ydrogenation ydrogen halide addition Br Br (Br 2 ) ( 2 ) (with 2 S 4 catalyst) Br l Br alogenation ydration *hydrogenation used for making saturated fats from unsaturated fats (S Exam 2010) No 10
Reactions of Alkenes Alkanes (e.g. 3 3 ethane), due to the lack of the double bond, D NT undergo addition reactions This allows alkenes and alkanes to be readily distinguished from each other For example, if an alkene is present, addition of an orangered solution of Br 2 in a solvent leads to almost instantaneous decolourisation of the Br 2 No 11
Reactions of Alkenes Distinguishing between alkanes and alkenes examined 2008 Q16; 2005 Q16; addition Br 2 to an unsaturated compound was examined 2009 Q6; 2010 Q11, Q24; 2011 Q11; 2013 Q8 No 12
Which compound can form when bromine water reacts with propene? (2011 Q11) int, draw the structure of propene and the product. 1. 1-bromopropane 2. 2-bromopropane 3. 1,1-dibromopropane 4. 1,2-dibromopropane 0% 0% 0% 0% 1. 2. 3. 4. No 13
An organic liquid, when reacted with concentrated sulfuric acid, produces a compound that decolourises bromine water. What is the formula of the organic liquid? (2010 Q11) 1. 6 12 2. 6 14 3. 6 11 4. 511 0% 0% 0% 0% 1. 2. 3. 4. No 14
Acid-Base Reactivity Depends on Partner 2 S 4 and the cockroach No 15
Reactions of Alkenes You should be able to write balanced equations for addition reactions, name the starting materials and products and be able to recognise the starting material, reagents used or product when given the other compounds No 16
With a partner name the starting alkene, then draw the expected product from treatment of the alkene with the reagent indicated 3 Reaction of Alkenes Questions p2 3 2-butene 2 and Ni 3 3 butane 3 3 l 3 l 3 3 3 2,3-dimethyl-2-butene 3 2 3 2-methylpropene Br 2 3 3 2-chloro-2,3-dimethylbutane Br Br 3 2 3 1,2-dibromo-2-methylpropane No 17
Reaction of Alkenes Questions With a partner draw and name the starting alkene in each case Br 2 and 2 Br 3 2 3 3 3 2 3 propene 2 and 2 S 4 (at) 3 3 No 18
Addition Polymers Small building-blocks (monomers) add together to form a polymer, with no atoms lost When ethene molecules combine together in addition polymerisation, polyethylene is formed 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 n No 19
Starting Monomers of ommon Addition Polymers and their uses Polymer Polymer Structure Monomer (Building Block) Examples of Use Polyethylene (LDPE and DPE) 2 2 n Polyvinyl chloride (Polychloroethene) 2 l n ethene l vinyl chloride LDPE: wrapping materials, carry bags, lining milk cartons, squeeze bottles, electrical insulation DPE: bowls, kitchen utensils, buckets, milk crates, freezer bags Electrical insulation, drainage pipes, guttering, garden hoses No 20
More Starting Monomers of ommon Addition Polymers and their uses Polymer Polymer Structure Monomer (Building Block) Examples of Use Polystyrene (Polyethenylbenzene) 2 n 2 Foam (drink cups, and packaging), tool handles, containers, insulation styrene (ethenylbenzene) Polytetrafluoroethylene PTFE, or Teflon (Polytetrafluoroethene) F 2 F 2 n F F F F tetrafluoroethylene (tetrafluoroethene) Non-stick cookware surfaces, electrical insulation, pipe thread sealant No 21
Teflon Information http://en.wikipedia.org/wiki/ Polytetrafluoroethylene Man skating on Teflon No 22
Addition Polymers Properties For a given type of polymer, the longer the polymer chain (higher molecular weight), the higher the melting point and the harder the substance is The less branched a polymer is, the more ordered the chains are and more crystalline the substance is. This leads to a more dense, higher melting point, tough and hard substance The bigger the side group, the less flexible the substance is, e.g. polystyrene (benzene, 6 5 group) is typically a hard, stiff plastic compared to polyethylene No 23
Addition Polymers Past Exams ow alkenes can be used to make new materials Identifying the monomer(s) or polymer in a polymerisation reaction (when given one of the two) Relating the properties exhibited by a polymer(s) to the structure of the polymer(s) and uses of that polymer(s) In 2011 needed to compare the properties of polystyrene with a biopolymer In 2012 needed to recognise polymerisation of ethene in the presence of a catalyst shown by using models In 2013 needed to show how polyetheylene and a biopolymer are formed No 24
Which polymer is made by the polymerisation of methyl methacrylate? (2003 S Q11) 3 2 3 methyl methacrylate Used to make perspex 1. 2 3 2 3 3 3 2 3 3 2. 2 3 3 3 2 2 3 3 3 3. 4. 3 3 3 3 3 3 3 3 3 3 3 3 0% 0% 0% 0% No 25
ondensation Polymers These are formed when the monomer units react together to eliminate (or kick-out, or remove, or lose ) a smaller molecule, which is often water arothers and colleagues examining the nylon stocking No 26
Reaction of a arboxylic Acid and an Amine The Formation of an Amide This is an example of a condensation reaction 3 2 2 2 2 N 2 2 2 2 2 3 hexanoic acid 1-aminohexane 3 2 2 2 2 N 2 2 2 2 2 3 new bond exyl hexanamide + 2 No 27
Reaction of a arboxylic Acid and an Alcohol The Formation of an Ester This is also an example of a condensation reaction 3 2 2 + conc. 2 S 4 3 3 2 2 3 1-propanol acetic acid (ethanoic acid) propyl acetate (propyl ethanoate) No 28
Difunctional Molecules ondensation of Amino Acids R R R R N N N N amino acid building blocks R = an attached group, for example, if R = 3, the amino acid is Alanine R N R N R N N R + 3 2 R a polypeptide N n denotes a new bond the repeat unit of a polypeptide No 29
Reaction of a Diacid and a Diamine Formation of a Polyamide (Nylon 6,6) - a condensation polymer ( 2 ) 4 N ( 2 ) 6 N ( 2 ) 4 N ( 2 ) 6 N 1,6-hexanedioic acid 1,6-diaminohexane ( 2 ) 4 N ( 2 ) 6 N ( 2 ) 4 N ( 2 ) 6 N + 3 2 a polymer N ( 2 ) 6 N ( 2 ) 4 n the repeat unit in nylon 6,6 No 30
Reaction of a Diacid and a Dialcohol Formation of a Polyester another example of a condensation polymer 2 2 2 2 1,2-ethanediol terephthalic acid 2 2 2 2 + 3 2 a polyester 2 2 n the repeat unit in polyethylene tetraphthalate, PET denotes a new bond 2005 S Exam needed to recognise monomers given the polymer No 31
Synthesis of Nylon 6,10 a Demonstration 2 N 2 2 2 2 2 1,6-diaminohexane 2 N 2 2 N 2 6 N 2 as a 5% (by weight) solution in water, with 1 pellet of sodium hydroxide + l 2 2 2 2 2 2 2 2 Sebacoyl chloride l l 2 8 l as a 5% (by weight) solution in hexane 2 8 N 2 nylon 6,10 6 N n No 32
ellulose condensation polymer of Glucose 6 2 5 6 2 4 4 1 5 2 1 3 2 3 Glucose Glucose in its puckered ring (chair) arrangement 4 6 2 Glucose is a -sugar (beta sugar), which means 5 that 6 and the group on 1 are on the same side (face) of the ring. 3 1 Glucose "stripped down" for clarity 2 2 2 n cellulose No 33
ellulose - an Important source ellulose contains basic building blocks for making starting molecules for petrochemicals, such as ethene (2 atoms), propene (3 atoms) and butene (4 atoms, a starting point for synthetic rubber) onsiderable scientific effort looking at cellulose as an alternative source of chemicals now obtained from oil Industries producing ethanol from cellulose for use as a biofuel No 34
ondensation Polymers Past Exams Identifying the monomer(s) or polymer in a polymerisation reaction (when given one of the two) Related to this questions are also often asked about esters, their properties, names and how made Recognising the structure of cellulose, that it is a condensation polymer formed from loss of water, is a major component of biomass, and is of interest as a source of chemicals we now obtain from oil Discussing preparation, properties and provide structures of polymers, including cellulose, was a feature of 2010, 2011 and 2013 exams No 35
Ethanol As a Solvent Ethanol is a commonly used solvent It is a polar molecule The - and - bonds are polar due to the atom being more electronegative than the and It can hydrogen-bond and undergo dipole-dipole interactions with polar molecules helping them to dissolve (like dissolves like) It also has a non-polar portion ( 3 ) which helps it dissolve less polar molecules - + + No 36
Ethanol Production Fermentation Ethene from catalytic cracking is the main industrial source of ethanol Fermentation is a process in which glucose (typically) is broken down to ethanol and carbon dioxide by the action of enzymes present in yeast A suitable grain or fruit is mashed up with water; yeast is added; air is excluded (anaerobic); and the mixture is kept at about 25-37 o Enzymes in the mixture convert any starch/sucrose to glucose and/or fructose and then glucose/fructose to ethanol and 2 6 12 6 (aq) 2 3 2 (aq) + 2 2 (g) No 37
Ethanol as Fuel Ethanol readily burns through a combustion/oxidation reaction to give carbon dioxide, water and energy 3 2 (l) + 3 2 (g) -> 2 2 (g) + 2 (g) + energy = -1360 kj/mol heat of combustion No 38
Ethanol as Fuel Ethanol is increasingly being used as a fuel due to it being a renewable resource referred to as biofuel ommonly being produced from starch or sugars from a wide variety of crops, including sugar cane and corn onsiderable debate due to land required for crops and energy-pollution balance (inc greenhouse gas) Ethtec, based in NSW, is developing methods to get ethanol from cellulosic waste such as wood, bagasse (waste from sugar production), crop stubble and municipal green waste No 39
Ethanol Past S Exams Production of ethanol from hydration and fermentation and comparison to catalytic cracking, its use as a solvent and comparison to water, combustion reactions of it and other alcohols and fuels, its use as a fuel, including the advantages and disadvantages, are all commonly assessed No 40
lickers No 41
For Further Information ontact A/Prof Joanne Jamie Phone: 9850 8283 Email: joanne.jamie@mq.edu.au Lecture notes will be made available soon at www.cbms.mq.edu.au/hsc_enrichment TANK YU AND GD LUK No 42