CHEM2522 Sustainable Chemical Manufacture

How CHEM2522 is assessed

What CHEM2522 covers

University of Sydney CHEM2522 Sustainable Chemical Manufacture runs in two halves, and this thirteen-chapter map follows the teaching schedule through both.

Chapters 1-6 cover the green-chemistry and process-chemistry half — the 12 principles and green metrics, the Diels-Alder, radical and photoredox chemistry, palladium cross-coupling, feedstocks and catalyst recovery — while Chapters 7-13 cover the polymer half, from chain conformation and molar-mass averages through step-growth, radical and coordination polymerisation to recycling, bio-based plastics and life-cycle analysis.

The unit is assessed by a 130-minute final written exam (a 20-mark multiple-choice section plus structured drawing/mechanism/calculation questions, with a data sheet and periodic table provided) alongside a laboratory course that carries an 80% attendance hurdle; use this map to see how each week's method builds toward that exam.

Weeks 1-6 are green and process chemistry — the 12 principles of green chemistry and the quantitative metrics that score a route (atom economy, E-factor, effective mass yield, % ideality), the Diels-Alder cycloaddition and frontier-molecular-orbital control, radical and photoredox chemistry, palladium cross-coupling, and the industrial realities of feedstocks, scale-up and catalyst recovery.

Weeks 7-13 are polymer science and sustainability — chain conformation and molar-mass averages, step-growth, radical chain-growth and coordination polymerisation, and end-of-life chemistry from recycling to microplastics and life-cycle analysis. The unit is a method-and-mechanism subject: marks come from drawing the right structure or mechanism, applying a datasheet formula with correct units, and interpreting the result.

Assessment runs through Canvas as a 130-minute final written exam — a 20-mark multiple-choice section plus structured questions (structures, mechanisms and green-chemistry / polymer calculations), with a data sheet and periodic table provided — together with a laboratory course of four experiments across about six sessions that carries an 80% lab-attendance hurdle (you must attend at least 80% of the lab sessions to pass).

The exact exam weight is not published in the unit materials (the USyd unit outline releases about two weeks before teaching), so confirm the weighting, the open- or closed-book status and the calculator policy on your Canvas Assessments page. The CHEM2522 result feeds the Weighted Average Mark (WAM) that later chemistry units build on.

CHEM2522 cheatsheet for exam revision

AskSia publishes a free CHEM2522 cheatsheet for exam revision, an exam cheat sheet that follows the official permitted-materials rule for this assessment and condenses the topics in this guide. Open the CHEM2522 cheatsheet.

Worked example · free

Two green metrics on an esterification: atom economy vs E-factor

Key terms

Atom economy

A best-case mass metric: (molar mass of the desired product ÷ molar mass of all reagents) × 100, catalyst disregarded. Highest (up to 100%) for addition, rearrangement and catalytic reactions; low for substitutions and eliminations that shed leaving groups.

E-factor

Mass of waste produced ÷ mass of desired product. Waste counts by-products, unreacted starting material, spent solvents and purification media. Typical values (Sheldon): oil refining ~0.1, bulk chemicals 1-5, fine chemicals 5-50, pharmaceuticals 25-100.

Frontier molecular orbitals (HOMO/LUMO)

The highest occupied and lowest unoccupied molecular orbitals. A reaction pairs the HOMO of one partner with the LUMO of the other; a smaller HOMO-LUMO gap and matching orbital symmetry give better overlap — the basis of Diels-Alder allowed/forbidden analysis.

Cross-coupling (Pd cycle)

A C-C (or C-N) bond-forming catalytic cycle on palladium: oxidative addition of Pd(0) into a C-X bond → transmetalation of the second partner → reductive elimination that forges the new bond and regenerates Pd(0).

Carothers equation

For step-growth polymerisation the number-average degree of polymerisation DP = 1/(1 - p), where p is the fractional conversion of functional groups; dispersity Đ = 1 + p → 2 at high conversion. Reaching high DP demands both high conversion and near-perfect stoichiometry.

Dispersity (Đ)

The breadth of a molar-mass distribution, Đ = Mw/Mn (always ≥ 1; = 1 is monodisperse). Step-growth polymers approach Đ = 2; controlled radical methods such as RAFT reach Đ ≈ 1.1-1.4.

CHEM2522 FAQ

Questions students ask in each CHEM2522 chapter

What is the difference between atom economy and E-factor?

Atom economy is a best-case calculation on the balanced equation — the fraction of reagent mass that ends up in the product if the reaction goes perfectly — so it depends only on the chemistry, not on how the reaction is run. The E-factor is a real measurement: total waste mass divided by product mass, including yield losses, unreacted reagents, solvents and workup media. A route can have a high atom economy and still a poor E-factor because solvent and purification waste dominate real processes; both appear on the exam data sheet because they answer different questions. Chapter 01 · Green Chemistry & Green Metrics

Why is the Diels-Alder called 'green' or atom-economical?

Because it is a concerted addition: the diene and dienophile combine to form the ring with no atoms lost, giving 100% atom economy. It also needs no polar solvent (there are no charged intermediates, so it can run neat), often no catalyst, and it builds a ring plus up to two stereocentres in a single step — hitting several of the 12 principles at once, which is exactly why Week 2 sits inside a sustainability unit. Chapter 02 · Pericyclic Reactions: the Diels-Alder

Why use NBS instead of just adding Br2 for allylic bromination?

Because free Br2 at high concentration adds ionically across the C=C double bond (electrophilic addition), which is not what you want. NBS keeps the bromine concentration very low by mopping up the HBr produced during propagation and releasing Br2 only in small amounts, so the slow radical pathway — H-abstraction at the allylic position followed by Br transfer — wins. Low [Br2] is the whole trick. Chapter 03 · Radical Reactions & Photoredox Catalysis

What is the difference between the named cross-couplings?

They share the same Pd(0)/Pd(II) cycle and differ mainly in the transmetalating partner and its activator: Kumada uses a Grignard (Mg, no base needed), Suzuki-Miyaura uses an organoboron (needs a base to form the boronate), Negishi uses an organozinc, Sonogashira couples a terminal alkyne with a copper(I) co-catalyst and an amine base, and Stille uses an organostannane (LiCl accelerates transmetalation, but tin is toxic). Buchwald-Hartwig makes C-N bonds by having the amine coordinate and a base deprotonate instead of a transmetalation. Learn the cycle once, then tabulate the partner and additive for each. Chapter 04 · Transition-Metal Cross-Coupling Catalysis

Why do we care about renewable feedstocks in a chemistry unit?

Because principle 7 of green chemistry is to use renewable feedstocks, and most bulk chemistry still starts from finite crude oil. Biomass — especially lignocellulose — can supply the same building blocks: lignin can be broken down to aromatic precursors (vanillin, guaiacol, syringol) that stand in for BTX, and cellulose can be converted through glucose and polyols to alkanes. Week 5 teaches you to trace both fossil and renewable routes to the same product so you can compare their sustainability. Chapter 05 · Industrial Chemistry I: Feedstocks & Scale-Up

How does HSAB tell me which scavenger to use?

Match softness. Palladium is a soft Lewis acid, so it forms its strongest bonds to soft Lewis bases — sulfur and phosphorus donors. That is why dithiocarbamates, thiols (QuadraSil-MP), thioureas (QuadraPure-TU) and phosphines (PBu3) are effective palladium scavengers, while a hard oxygen or nitrogen donor would bind it only weakly. In an exam answer, name a soft-donor scavenger and state the soft-acid/soft-base match explicitly. Chapter 06 · Industrial Chemistry II: Catalyst Recovery, Solvents & Flow

Why are there two different average molar masses?

Because a synthetic polymer is a distribution of chain lengths, and how you average depends on what you weight by. The number-average Mn weights every chain equally (it is what colligative and end-group methods 'see'), so the many short chains pull it down. The weight-average Mw weights by mass — the Mi^2 term on top — so long chains count more, and it is what light-scattering methods 'see'. Their ratio, the dispersity Đ = Mw/Mn, tells you how broad the distribution is. Chapter 07 · Introduction to Polymers

Why does step-growth need such high conversion for high molar mass?

Because in step-growth every functional group has to react to link chains, and the Carothers equation DPn = 1/(1 - p) is brutally sensitive near p = 1: p = 0.90 gives DP = 10, p = 0.99 gives DP = 100, p = 0.999 gives DP = 1000. Below ~99% conversion you only have oligomers. That is very different from chain-growth, where high molar mass appears almost immediately. Chapter 08 · Step-Growth Polymerisation

How does the termination mode change the molar mass?

Combination joins two live chain ends into one dead chain, so the product molar mass is about the sum of the two — roughly double a single growing chain. Disproportionation instead transfers a hydrogen from one chain to the other, ending both without joining them, so each stays at its own length (one gets a saturated end, one a terminal double bond). Methacrylates favour disproportionation because of their abstractable alpha-hydrogens and hindered ends, whereas styrene tends to combine. Chapter 09 · Radical Chain-Growth Polymerisation

How does coordination polymerisation differ from radical polymerisation?

In coordination polymerisation the chain grows by insertion at a metal centre, which controls how each monomer adds — so you get linear chains with defined stereochemistry (tacticity) and can copolymerise precisely. Radical polymerisation grows through free radical chain ends with far less control, and side reactions like back-biting graft branches. That control is why coordination catalysts make linear HDPE and stereoregular polypropylene, while the radical high-pressure process makes branched LDPE. Chapter 10 · Coordination Polymerisation: Ziegler-Natta & Metallocene

What is the difference between ceiling temperature and decomposition temperature?

The ceiling temperature Tc is a thermodynamic equilibrium point: above it, depolymerisation (chains going back to monomer) outpaces polymerisation. The decomposition temperature is where a polymer simply breaks apart thermally into a mixture of smaller molecules. A polymer with a low ceiling temperature can be unzipped cleanly back to monomer for closed-loop chemical recycling, whereas one that only decomposes gives a broad product mixture. Comparing the two tells you how recyclable-to-monomer a polymer is. Chapter 11 · Polymer Recycling & Waste

How is chemical recycling different from mechanical recycling?

Mechanical recycling melts and remoulds the polymer, so quality falls with each cycle and contamination is a big problem. Chemical recycling instead breaks the polymer back to its monomers (for PET, by hydrolysis, glycolysis, methanolysis or enzymatic PETase), which can then be purified and re-polymerised into virgin-quality material. That makes true closed-loop recycling possible, at the cost of more energy and processing. Chemical recycling is the answer to the quality-loss limits of mechanical recycling seen in Week 11. Chapter 12 · Chemical Recycling & Bio-Based Plastics

Where do microplastics actually come from?

Mostly from everyday wear and fragmentation rather than deliberate microbeads. The largest contributors are synthetic microfibres shed when washing textiles (~35%), tyre wear from driving (~28%) and general fragmentation of larger plastic litter (~22%), with smaller inputs from nurdles (pre-production pellets), cosmetic microbeads and paint. Once released they are persistent, disperse widely and can enter the food chain, which is why source-level design (durable textiles, better tyres, less unnecessary plastic) matters more than clean-up alone. Chapter 13 · Microplastics & Life-Cycle Analysis

How to study for the exam

Treat CHEM2522 as two linked skill sets rather than one reading unit, and rehearse both weekly rather than cramming through STUVAC.

For the Weeks 1-6 process half, redraw each week's mechanism from memory — the Diels-Alder [4+2] with endo/exo, a radical chain, the full Pd(0)/Pd(II) cross-coupling cycle — and work one green-metric calculation end to end (atom economy and E-factor on the same route, so you feel why they disagree).

For the Weeks 7-13 polymer half, drill the datasheet calculations until they are automatic: Carothers DP = 1/(1 - p) and the stoichiometric-imbalance form, Mn/Mw/dispersity from a mixture, and the Kuhn-length random-flight relations. Because the exam provides the data sheet and periodic table, practise applying the formulas with correct units and a sanity check, not memorising them.

Build a one-page map of named reactions and named polymers (which coupling uses which partner; which polymer is step- vs chain- vs coordination-growth) because the multiple-choice section rewards fast recall. Cover breadth first — you want to be able to start every topic — then deepen the ones you find hardest.

When a step won't click, ask Sia to explain that single step a different way and set you a fresh practice question in the same style; it teaches the method and checks your reasoning, and it never substitutes for your own graded work. Confirm the exam date, room, weighting and open/closed-book status on Canvas and the University of Sydney exam timetable.

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