CHEM2522 Sustainable Chemical Manufacture is challenging mainly because it spans two integrated halves — making the molecule (synthesis and polymers) and proving what you made (spectroscopy) — both judged against green-chemistry metrics. It rewards reflexes rather than recall: reading a structure and predicting its spectra, reading spectra and deducing the structure, and judging the atom economy of any route. Build those skills and it becomes manageable.

What topics does CHEM2522 cover?

The unit covers green chemistry (the 12 principles), sustainability metrics (atom economy, E-factor, process mass intensity), feedstocks, catalysis (homogeneous vs heterogeneous, TON/TOF), structure elucidation (degrees of unsaturation, IR, mass spectrometry, 1H and 13C NMR), organic mechanisms (SN1, SN2, E1, E2, carbonyl chemistry, named C–C bond formation), oxidation and reduction, and polymer chemistry (chain- vs step-growth, molar mass and dispersity, Tg/Tm, tacticity, sustainable and biodegradable polymers).

How do you calculate atom economy in CHEM2522?

Atom economy is the molar mass of the desired product divided by the sum of the molar masses of all products from the balanced equation, times 100. For example, hydration of ethene to ethanol is 100% (no by-product), while fermentation of glucose to ethanol is about 51% because CO2 is lost. Addition and rearrangement reach 100%; substitution and especially elimination or condensation lose atoms.

How do you tell SN1 from SN2 in CHEM2522?

SN2 is a one-step concerted reaction that favours primary substrates, strong nucleophiles and polar aprotic solvents, and gives inversion of configuration. SN1 is a two-step reaction through a carbocation that favours tertiary substrates and polar protic solvents and gives racemisation. A strong bulky base plus heat pushes toward elimination instead.

What spectroscopy techniques are tested in CHEM2522?

Mass spectrometry gives molecular formula and mass (with the nitrogen rule and Cl/Br isotope patterns), infrared spectroscopy identifies functional groups (the C=O region around 1670–1750 cm⁻¹ is key), and 1H and 13C NMR (with DEPT) reveal the carbon–hydrogen skeleton through chemical shift, integration and multiplicity. Always start by calculating degrees of unsaturation from the molecular formula.

What is the difference between chain-growth and step-growth polymers?

Chain-growth (addition) polymerisation adds vinyl monomers to an active centre with no by-product, reaching high molar mass early — examples include PE, PP, PVC and PS. Step-growth (condensation) polymerisation links bifunctional monomers and often expels a small molecule such as water, reaching high molar mass only near complete conversion (Carothers equation) — examples include nylon, PET and polyurethane.

Why is catalysis considered green chemistry?

A catalyst lowers the activation energy by providing an alternative pathway, is not consumed, and improves selectivity. It replaces stoichiometric reagents so there is less waste and enables milder conditions so there is less energy use. A high turnover number means a small amount of catalyst does a lot of work, which is the green prize — recyclable heterogeneous catalysts are especially favoured.

Is the CHEM2522 exam open or closed book?

Exam conditions, weighting and assessment structure are set by the University of Sydney and can change between offerings, so confirm the open- or closed-book status and the full assessment breakdown in the official CHEM2522 unit outline. This cheat sheet is a revision aid that maps the syllabus, not a statement of exam rules.

CHEM2522

Sustainable Chemical Manufacture

University of Sydney · School of Chemistry

Exam Revision
Sem 1 2026 · Side 1 of 2
Whole-unit revision · all topics

SIDE 1/2 ANALYSE · Green chemistry · Sustainability metrics · Feedstocks · Catalysis · Structure elucidation · IR · MS · ¹H & ¹³C NMR Revision sheet · all topics Compiled by AskSia · mapped to the CHEM2522 syllabus · asksia.ai/cheatsheet/usyd-chem2522

0 · Revision Blueprintread first

This unit has two halves that share one mindset: make the molecule (synthesis + polymers) and prove what you made (spectroscopy) — both judged against the green-chemistry yardstick of doing it with the least waste, energy and hazard.

Side 1 = analysis & sustainability metrics. Side 2 = reactions & polymers. The exam reflex you need: read a structure, predict its spectra; read spectra, deduce the structure; and for any route, judge its atom economy.

Most-tested skills: calculate atom economy / E-factor; assign an IR + MS + NMR set to one structure; pick Sₙ1 vs Sₙ2; classify a polymerisation; name a greener alternative (solvent, catalyst, feedstock).

Sia → Two-line discipline: always state degrees of unsaturation first in any structure problem, and always quote the metric (a number) when asked "is this green?" — markers reward the calculation, not the adjective.

1 · Green Chemistry · 12 PrinciplesAnastas & Warner 1998

The design framework for the whole unit. Memorise the mnemonic "PRODUCTIVELY" idea — but really know the high-yield five (★).

Prevent waste — better than treating/cleaning it up
Atom economy — maximise atoms of reactant in product
Less hazardous synthesis (low toxicity to people/environment)
Design safer chemicals (function with minimal toxicity)
Safer solvents/auxiliaries — avoid where possible
Design for energy efficiency — ambient T & P
Renewable feedstocks not depleting ones
Reduce derivatives (protecting groups add waste steps)
Catalysis > stoichiometric reagents
Design for degradation — break down after use, no persistence
Real-time analysis to prevent pollution
Inherently safer chemistry (accident prevention)

Prevention > remediation is the spine: principles 1, 2, 9 do most of the exam work.

1b · Worked · Atom Economytwo routes

Target = ethanol (C₂H₆O, M_r 46):

Hydration CH₂=CH₂ + H₂O → C₂H₅OH
AE = 46/(28+18) = 100% (addition, no by-product).

Fermentation C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂
AE = (2·46)/180 = 51% — CO₂ is lost mass, but the feedstock is renewable.

⇒ greenness trades AE vs feedstock vs energy. Quote all three, don't crown a winner on AE alone.

2 · Sustainability Metricscalculate these

Yield tells you nothing about waste. A 100% yield reaction can still be wasteful if half the reactant mass ends up as by-product. That's why we measure atoms and mass.

Atom economy Trost 1991

% atom economyAE = (M_r desired product / Σ M_r all products) × 100
= M_r product / Σ M_r reactants × 100

Theoretical (uses the balanced equation, ignores yield). Addition & rearrangement → 100% AE; substitution & especially elimination/condensation lose atoms.

E-factor Sheldon

Environmental factorE = mass of waste / mass of product
ideal E = 0 (zero waste)

Industry	Tonnage	E-factor
Bulk chems	10⁴–10⁶	<1–5
Fine chems	10²–10⁴	5–50
Pharma	10–10³	25–>100

Smaller-tonnage, higher-value products are the dirtiest per kg — pharma is the big target.

Process Mass Intensity

PMI & RMEPMI = total mass in / mass product (PMI = E + 1)
RME = mass product / Σ mass reactants × 100

PMI includes solvent & water — usually the largest mass in a process, which AE ignores.

3 · Feedstocksrenew vs deplete

Non-renewable: crude oil, natural gas, coal → cracked to platform chemicals (ethene, propene, BTX = benzene/toluene/xylene). Finite, CO₂-emitting.

Renewable: biomass — sugars, cellulose/lignocellulose, plant oils, terpenes. Bio-platform molecules: ethanol, lactic acid, succinic acid, HMF, glycerol (biodiesel by-product).

Tension: 1st-gen (food crops) vs 2nd-gen (waste lignocellulose) — the latter avoids the food-vs-fuel problem. Renewable ≠ automatically green (land, energy, processing all count).

3b · CO₂ & C1 Feedstockswaste → resource

Use abundant one-carbon sources as raw material: CO₂ → urea, cyclic carbonates, salicylic acid, and (with H₂) methanol; syngas (CO + H₂) → methanol, Fischer–Tropsch hydrocarbons.

Drop-in bio-chemicals = chemically identical to the fossil version (bio-ethene) ⇒ slot straight into existing plants. Novel bio-chemicals = new structures (lactic acid → PLA).

4 · Catalysis · Fundamentalsprinciple 9

A catalyst lowers Eₐ by providing an alternative pathway, is regenerated, and is not consumed. It speeds both directions equally — so it does not shift the equilibrium position or change ΔG/K; it only changes the rate.

Why it's green: replaces stoichiometric reagents (less waste), enables milder conditions (less energy), and improves selectivity.

Selectivity — 4 types

Chemoselective — one functional group over another
Regioselective — one position/orientation
Stereoselective — one diastereomer
Enantioselective — one enantiomer (asymmetric catalysis)

Homogeneous vs heterogeneous

	Homo	Hetero
Phase	same as reactants	different (usually solid)
Selectivity	high, tunable	lower
Separation	hard (energy cost)	easy, recyclable
Example	Wilkinson's, Pd	Ziegler–Natta, zeolites

Activity metrics

TurnoverTON = mol product / mol catalyst
TOF = TON / time = catalyst productivity rate

High TON ⇒ a little catalyst does a lot ⇒ greener.

5 · Catalysis · Typesknow examples

Acid/base — protonation/deprotonation steps
Organometallic — Pd/Rh/Ru; oxidative addition → migratory insertion → reductive elimination cycle
Biocatalysis — enzymes; water, mild T/pH, exquisite enantioselectivity
Organocatalysis — small organic molecules, metal-free (List & MacMillan, Nobel 2021)
Photoredox — light drives single-electron steps

Asymmetric hydrogenation (chiral metal complex) and enzyme catalysis are the classic "how to make one enantiomer cleanly" answers.

5b · Worked · TON / TOFhow green

0.001 mol catalyst makes 0.8 mol product in 2 h:

TON = 0.8 / 0.001 = 800
TOF = 800 / 2 = 400 h⁻¹

Industrial/enzyme catalysts reach TON 10⁶–10⁹. Real TON is capped by deactivation (poisoning, leaching, sintering) — recyclability is the green prize.

6 · Structure Elucidationthe workflow

Combine the techniques — each answers a different question:

MS → molecular formula & mass (what's the size?)
IR → functional groups (what's attached?)
¹H/¹³C NMR → carbon–hydrogen skeleton (how connected?)

Step 1 always: DBE

Degrees of unsaturation (IHD/DBE)DBE = (2C + 2 + N − H − X) / 2
(O is ignored). Ring or π-bond = 1 each.

DBE ≥ 4 ⇒ suspect a benzene ring (3 C=C + 1 ring). C=O = 1, C≡N = 2, C≡C = 2.

Sia → DBE first, every time — it tells you how many rings/multiple bonds to "spend" before you draw a single line.

7 · IR Spectroscopycm⁻¹

Bond stretching frequency ∝ √(k/μ): stronger bond & lighter atoms ⇒ higher cm⁻¹. Read the diagnostic 4000–1500 region; 1500–500 is the "fingerprint".

Bond / group	cm⁻¹	Note
O–H alcohol	3200–3550	broad
O–H carb. acid	2500–3300	v. broad
N–H amine/amide	3300–3500	1–2 bands
C–H sp³ / sp²	<3000 / >3000	key split
≡C–H alkyne	~3300	sharp
C≡N / C≡C	2210–2260	weak/sharp
C=O	1670–1750	strong ★
C=C alkene	1620–1680	weak
aromatic C=C	1450–1600
C–O	1000–1300	strong

C=O fine print: amide ~1650 < acid ~1710 ≈ ketone 1715 < aldehyde 1725 < ester 1735 < acyl chloride 1800. Conjugation lowers C=O by ~30.

7b · Reading an IR Spectrum3 questions

C=O? strong, sharp 1650–1750 ⇒ carbonyl present
Broad O–H / N–H? 2500–3550 ⇒ acid/alcohol/amine
C–H above or below 3000? ⇒ sp²/aromatic vs sp³

Tell-tales: aldehyde = C=O + twin C–H (Fermi) ~2720/2820; nitrile = sharp 2250; anhydride = two C=O bands.

7c · Distinguish by IRisomer trap

Group	O–H/N–H	C=O
Carb. acid	broad 2500–3300	~1710
Ester	none	1735 + strong C–O
Ketone	none	~1715 only
Amide	N–H ~3300	~1650
Alcohol	broad ~3300	none

8 · Mass Spectrometrym/z

M⁺• molecular ion = relative molecular mass. Then bonds fragment to give a pattern of cations.

Diagnostic rules

Nitrogen rule: odd M⁺ ⇒ odd number of N atoms
M+1 ≈ 1.1% × (number of C) — counts carbons
Cl: M:M+2 ≈ 3 : 1
Br: M:M+2 ≈ 1 : 1

Common neutral losses

Δm	Lost	Implies
15	•CH₃	methyl
18	H₂O	alcohol
28	CO / C₂H₄	carbonyl
29	CHO / C₂H₅	aldehyde
31	•OCH₃	methyl ester
45	COOH	carb. acid

Key fragments: m/z 43 = CH₃CO⁺ (acylium), 91 = tropylium (benzylic), 77 = phenyl. α-cleavage & McLafferty (γ-H transfer, loses an alkene from carbonyls) are the named fragmentations.

9 · ¹H NMRδ / ppm

Three readings: shift δ (environment), integration (relative # H), multiplicity (neighbours).

Splittingn equivalent neighbours ⇒ n + 1 peaks
J (coupling constant, Hz) shared by coupled partners

Proton	δ ppm
TMS (ref)	0
R–CH₃ / CH₂ / CH	0.8–1.7
C–H α to C=O	2.0–2.6
C–H next to N	2.2–2.9
C–H next to O / X	3.3–4.5
alkene =C–H	4.5–6.5
aromatic Ar–H	6.5–8.0
aldehyde CHO	9.5–10
carb. acid COOH	10–12

OH/NH = broad, variable, exchange with D₂O (peak vanishes ⇒ confirms OH/NH).

9b · Coupling Patternsrecognise instantly

Group	Pattern
–CH₂CH₃ (ethyl)	triplet 3H + quartet 2H
(CH₃)₂CH– (iPr)	doublet 6H + septet 1H
–OCH₃ / isolated CH₃	singlet (no neighbours)
para-disubst. ring	2 doublets (AA′BB′)

Equivalent H (by symmetry) = one signal & don't split each other. n+1 counts H on adjacent carbons only.

10 · ¹³C NMR + DEPTδ / ppm

Counts unique carbons (no integration; ¹H-decoupled = singlets). Wide 0–220 ppm range.

Carbon	δ ppm
alkyl C	0–50
C–N	30–60
C–O	50–90
alkyne C	65–90
alkene / aromatic	100–150
C=O acid/ester/amide	160–185
C=O ketone/aldehyde	190–220

DEPT

Edits by # attached H: CH & CH₃ up, CH₂ down, quaternary C absent (the give-away for C=O & substituted aromatic).

Counting signals = symmetry

# of signals = # of chemically distinct environments. Benzene = 1 ¹³C; para-disubstituted ring = 4 (two pairs equivalent). Fewer signals than carbons ⇒ symmetry — a fast structural clue.

11 · Worked · C₄H₈Oput it together

MS M⁺ = 72. DBE = (2·4+2−8)/2 = 1 ⇒ one C=O or C=C/ring.

IR 1715 cm⁻¹ strong ⇒ ketone C=O (no broad O–H, no ~2720 aldehyde C–H, no 1735 ester).

¹H NMR triplet 1.0 (3H), quartet 2.4 (2H), singlet 2.1 (3H) ⇒ ethyl + isolated methyl on C=O.

⇒ butan-2-one, CH₃COCH₂CH₃. MS loss of 15 (→57) and 29 (→43, CH₃CO⁺) confirm α-cleavage either side of C=O.

Sia → Reconcile every piece of data to one structure — if a single peak doesn't fit, the structure is wrong. Examiners build the trap on the one ignored signal.

11b · Worked · C₈H₈Ospot the ring

DBE = (2·8+2−8)/2 = 5 ⇒ benzene ring (4) + one more (a C=O).

IR 1685 (conjugated C=O). ¹H: 5H multiplet 7.4–8.0 (mono-substituted ring) + singlet 2.6 (3H, CH₃CO).

⇒ acetophenone, C₆H₅COCH₃. ¹³C ~198 (C=O); m/z 105 (PhCO⁺) & 77 (C₆H₅⁺) confirm.

Which Technique?recap

Question	Use
Mass / formula	MS (M+1, isotopes)
Functional groups?	IR (C=O, O–H, N–H)
# unique C; C type	¹³C + DEPT
H count & connectivity	¹H (δ, integ, J)
Rings / π count	DBE from formula

Formula Beltside 1

AE = M_r(prod)/ΣM_r(react) ×100
E = waste / product · PMI = E+1
DBE = (2C+2+N−H−X)/2
splitting = n+1 · M+1 ≈ 1.1%·nC
Cl 3:1 · Br 1:1 (M:M+2)

CHEM2522

Sustainable Chemical Manufacture

University of Sydney · School of Chemistry

Exam Revision
Sem 1 2026 · Side 2 of 2
Synthesis · mechanisms · polymers

SIDE 2/2 MAKE · Functional groups · Substitution/elimination · Carbonyl · Named C–C coupling · Redox · Polymers · Sustainable polymers Revision sheet · all topics Compiled by AskSia · mapped to the CHEM2522 syllabus · asksia.ai/cheatsheet/usyd-chem2522

12 · Functional Groupsreactivity map

Reactivity lives at the functional group; the carbon skeleton is mostly inert. Two master patterns:

Polar / ionic — a nucleophile (electron-rich, δ−) attacks an electrophile (electron-poor, δ+). Curly arrows go from Nu to E.
Radical — homolysis, single-electron (fish-hook) arrows; chain initiation/propagation/termination.

Electrophilic carbons: C–X (halide), C=O (carbonyl). Nucleophiles: OH⁻, RO⁻, CN⁻, NH₃, enolates, RMgX (carbanion equiv.).

13 · Substitution & EliminationSₙ1/2 · E1/2

	Sₙ2	Sₙ1
Steps	1 (concerted)	2 (carbocation)
Rate	k[RX][Nu]	k[RX]
Substrate	1° > 2°	3° > 2°
Stereo	inversion	racemisation
Solvent	polar aprotic	polar protic
Nu	strong	weak ok

E2: concerted, anti-periplanar H & LG, strong base, rate k[RX][base]; E1: via carbocation, rate k[RX]. Both follow Zaitsev (more-substituted alkene) — except a bulky base (t-BuO⁻) gives Hofmann (less-substituted).

The fork: strong bulky base + heat ⇒ elimination; good Nu, weaker base ⇒ substitution. 3° + weak Nu/protic ⇒ Sₙ1/E1 mix.

13b · Nucleophiles & Leaving Groupsrank them

Leaving group best→worst: I⁻ > Br⁻ > Cl⁻ ≫ F⁻; TsO⁻ & H₂O good. A weak base is a good LG (stable once it leaves); OH⁻, RO⁻, NH₂⁻ are poor LGs.

Nucleophilicity ↑ with negative charge & less steric bulk. Basicity ≠ nucleophilicity: in polar aprotic they track; in polar protic the bigger, more-polarisable ion wins (I⁻ > F⁻).

13c · Carbocation Stabilitydrives Sₙ1/E1

Order 3° > 2° > 1° > methyl (hyperconjugation + induction); benzylic/allylic are extra-stable (resonance).

An unstable cation rearranges (1,2-hydride or alkyl shift) to a more stable one — the classic Sₙ1/E1 "wrong product" trap.

13d · Mechanism Arrowsmethod marks

Arrow starts at a lone pair or bond, points where electrons go
Never start an arrow at H⁺ or a + charge
Conserve charge & atoms each step
Double-head = 2e⁻ (polar); fish-hook = 1e⁻ (radical)

14 · Carbonyl ChemistryC=O

The carbonyl C is electrophilic (δ+); O is the basic/nucleophilic end. Two regimes:

Aldehydes & ketones

Nucleophilic addition — Nu adds to C, O becomes O⁻/OH. e.g. + RMgX → alcohol; + NaBH₄ → alcohol; + H₂O → hydrate; + ROH → acetal; + amine → imine.

Carboxylic acid derivatives

Nucleophilic acyl substitution (addition–elimination): Nu adds, then the leaving group leaves, C=O reforms.

Reactivity (LG ability)acyl chloride > anhydride > ester ≈ acid > amide
can convert "downhill" only

Enolates / aldol

α-C–H is acidic (~pKa 20) ⇒ base gives an enolate nucleophile → aldol (β-hydroxy carbonyl), then dehydration to enone. Key C–C bond-forming chemistry.

15 · Named C–C Bond Formationbuild the skeleton

Grignard RMgX + C=O → 2°/3° alcohol (carbanion adds)
Aldol enolate + carbonyl → β-hydroxy carbonyl
Wittig ylide + C=O → alkene (makes C=C cleanly)
Pd cross-coupling — Nobel 2010:

Name	Couples
Suzuki	R–X + R'–B(OH)₂
Heck	R–X + alkene
Sonogashira	R–X + terminal alkyne

Cycle: oxidative addition → transmetalation → reductive elimination. Catalytic in Pd, mild, tolerant of functional groups ⇒ green & widely used in pharma.

15b · Imines, Acetals & Protecting Groupscarbonyl + N/O

Carbonyl + 1° amine → imine (C=N); + 2° amine → enamine. Acid-catalysed, water removed to drive the equilibrium.

Carbonyl + 2 ROH → acetal = a protecting group for C=O (stable to base & nucleophiles, removed by aqueous acid). But every protecting group adds steps ⇒ poor atom economy (principle 8 — reduce derivatives).

15c · Enols & Conjugate Additionα & β reactivity

Keto–enol tautomerism: the keto form dominates, but the enol is the nucleophile in α-substitution (halogenation, the aldol).

α,β-unsaturated carbonyl is electrophilic at the carbonyl C (1,2-addition) and at the β-C: 1,4 / Michael / conjugate addition. Soft nucleophiles & stabilised enolates favour 1,4.

16 · Oxidation & Reductionthe toolkit

Oxidation (add O / remove H)

1° alcohol → aldehyde (PCC, Swern, TEMPO) → acid (KMnO₄, CrO₃/Jones). 2° alcohol → ketone. Green oxidants: O₂, H₂O₂ (by-product = H₂O), catalytic TEMPO.

Reduction (add H / remove O)

Reagent	Strength	Reduces
NaBH₄	mild	aldehyde, ketone
LiAlH₄	strong	+ ester, acid, amide
H₂ / Pd	catalytic	C=C, hydrogenation

Catalytic H₂ is greenest (atom-economic, no metal-hydride waste). Chemoselectivity: NaBH₄ leaves esters/acids alone.

Greener redox

Replace toxic Cr(VI) & heavy-metal oxidants with O₂ / H₂O₂ (by-product = H₂O) + catalytic TEMPO; use catalytic hydrogenation or enzymatic reduction over stoichiometric hydrides.

17 · Polymers · Two Routesclassify first

	Chain-growth	Step-growth
Monomer	C=C (vinyl)	2 functional groups
Mech.	active centre adds monomer	any two ends react
MW vs time	high early	high only near 100%
By-product	none (addition)	small molecule (H₂O)
Examples	PE, PP, PVC, PS, PMMA	nylon, PET, PU

Carothers (step-growth)X̄_n = 1 / (1 − p) · p = conversion
⇒ need p > 0.99 for useful chain length

Addition vs condensation = does it lose a small molecule? Addition keeps every atom (100% AE); condensation expels H₂O ⇒ lower AE.

17b · Copolymers2+ monomers

Arrangement tunes properties: random (–ABBABA–), alternating (–ABAB–), block (–AAA·BBB–, needs living polymerisation), graft (B branches off an A backbone).

Block copolymers self-assemble into thermoplastic elastomers (e.g. SBS rubber) — precision delivered by controlled radical (RAFT/ATRP).

17c · Identify the Routeexam reflex

Given a monomer or repeat unit:

A C=C & repeat unit = same atoms as monomer ⇒ addition / chain-growth
Two functional ends + a small molecule (H₂O) lost ⇒ condensation / step-growth
Ester links in backbone ⇒ polyester (PET); amide links ⇒ polyamide (nylon)

18 · Addition Polymerisationchain-growth

Radical (free-radical)

Initiation — initiator (AIBN, BPO) homolyses → R•
Propagation — R• + monomer → new chain radical, repeats
Termination — combination or disproportionation of two radicals

Cheap, robust (PE, PS, PVC) but poor control of MW/architecture. RAFT / ATRP = controlled "living" radical → narrow Đ, block copolymers (a green/precision advance).

Coordination — Ziegler–Natta / metallocene

Transition-metal catalyst inserts monomer stereoregularly ⇒ controls tacticity & linearity (HDPE, isotactic PP). Heterogeneous, recyclable catalyst.

19 · Condensation Polymersstep-growth

Polyester (PET) — diacid + diol → ester links + H₂O. Bottles, fibres.
Polyamide (nylon) — diacid + diamine → amide links + H₂O.
Polyurethane — diol + diisocyanate (no by-product; addition-type step-growth).
Polycarbonate — bisphenol + carbonate source.

Need exact stoichiometry & high purity (Carothers) for high MW. The ester/amide links are also the handle for chemical recycling (hydrolysis/solvolysis back to monomer).

19b · Nature's Step-Growthbiopolymers

The largest condensation polymers are biological: proteins (amino acids → peptide/amide bonds + H₂O), polysaccharides (sugars → glycosidic bonds + H₂O), nucleic acids (phosphodiester). All are hydrolysable ⇒ inherently degradable — the design template for sustainable polymers.

19c · Worked · Carotherswhy purity matters

Degree of polymerisation vs conversion p:

p	X̄_n = 1/(1−p)
0.90	10
0.95	20
0.99	100
0.995	200

⇒ step-growth needs near-complete conversion for useful chain length. A single impurity or stoichiometric imbalance caps M — hence the purity demand.

20 · Polymer Propertiesstructure→property

Molar mass

Averages & dispersityM̄_n = Σn_iM_i/Σn_i (number avg)
M̄_w = Σn_iM_i²/Σn_iM_i (weight avg)
Đ = M̄_w/M̄_n ≥ 1 (dispersity)

Đ = 1 ⇒ perfectly uniform; step-growth ~2; controlled radical → low Đ.

Thermal & order

T_g glass transition (amorphous softens); T_m melts (crystalline)
Tacticity — iso / syndio / atactic; regular ⇒ crystalline, higher T_m
Thermoplastic (linear, re-meltable, recyclable) vs thermoset (cross-linked, cannot re-melt) vs elastomer

Crystallinity ↑ ⇒ stronger, stiffer, more opaque, higher T_m.

21 · Sustainable Polymersprinciples 7 & 10

Bio-based (renewable feedstock): PLA (polylactic acid, from corn/sugar), PHA/PHB (bacterial), starch, cellulose.

Biodegradable ≠ bio-based — they're independent. PLA is both; bio-PE is bio-based but not biodegradable. Design for degradation = build in hydrolysable links.

Recycling hierarchy

Mechanical — remelt/reform (thermoplastics; quality degrades)
Chemical — depolymerise to monomer (PET glycolysis/methanolysis) ⇒ closed-loop / circular
Energy recovery (last resort)

21b · Structure → Propertyquick rules

Branching ↓ ⇒ packs tighter ⇒ denser & stronger (HDPE > LDPE)
Cross-linking ↑ ⇒ rigid, insoluble thermoset (rubber vulcanisation)
Chain length / M ↑ ⇒ higher T_m, strength, viscosity
Polar groups / H-bonds (nylon) ⇒ stronger, higher T_m
Plasticiser ⇒ lowers T_g (rigid PVC → flexible)

21c · Measuring Molar Massmethods

GPC / SEC — size-exclusion; gives the full distribution → M̄_n, M̄_w, Đ
End-group analysis (NMR/titration) → M̄_n (low MW only)
Osmometry → M̄_n; light scattering → M̄_w

M̄_w ≥ M̄_n always ⇒ Đ ≥ 1; broad Đ ⇒ wide spread of chain lengths.

22 · Greener Process Toolkitprinciples 5,6,9

Green solvents — water, scCO₂, ionic liquids, bio-solvents (2-MeTHF, ethanol); avoid chlorinated & VOCs
Biocatalysis — enzymes; mild, aqueous, enantioselective
Flow chemistry — continuous, better heat/mass transfer, safer, scalable (process intensification)
Catalysis > stoichiometric reagents everywhere
Avoid protecting groups (principle 8 — reduce derivatives)

23 · Worked · Atom Economyshow the number

Q. Wittig vs substitution to make an alkene — which is greener by AE?

Wittig expels Ph₃P=O (M_r 278) — a large by-product ⇒ low atom economy despite high yield. An elimination or a catalytic metathesis keeps more atoms in product.

Lessonhigh yield ≠ green. Quote AE/E-factor,
then name the by-product driving waste.

24 · Exam Disciplinedon't lose marks

State DBE before drawing any structure
Assign every spectral peak — reconcile to one structure
"Is it green?" ⇒ give a number + name the waste
Mechanisms: curly arrows from Nu→E, charges & lone pairs shown
Classify polymer route before drawing the repeat unit
Don't confuse yield with atom economy

Sia → Half the marks here are "show the calculation / show the arrow." Method marks survive even when the final number slips — always write the working.

25 · Green Metrics Recapname the trade-off

Metric	Captures	Misses
Atom economy	by-products (theory)	yield, solvent
Yield	conversion achieved	waste atoms
E-factor	real total waste	toxicity
PMI	+ solvent & water	hazard

No single number means "green" — name which trade-off the question tests.

Formula Beltside 2

X̄_n = 1/(1−p) · Đ = M̄_w/M̄_n ≥1
splitting n+1 · reactivity: RCOCl>ester>amide
Sₙ2 inversion · E2 anti-periplanar
green: catalysis · renewable · degrade