Learning Arc 02 · Build electron, stereochemical and substitution grammar
Demonstrate substitution mastery
- Examinations mix representations and evidence.
- Mastery means connecting every row without a memorised jump.
Foundation for this Concept12 symbols · 0 recovery lessons · 1 entry checksOpen
Start here: words and symbols used in this Concept
Open only the recovery material you need before the Mystery.
Read these words and symbols first
- case file
- One substrate, condition set and observation set analysed together.
- Evidence from a different experiment cannot be imported silently.
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- delayed retrieval
- A rule is used after its worked example is no longer beside the Question.
- The learner reconstructs the rule rather than copying a nearby pattern.
- mark-bearing row
- One independently scorable claim with its reason or evidence.
- Several vague claims in one paragraph do not replace separate scored rows.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
- supplied-data response
- An answer derived from data and definitions printed in the Question.
- The AP-style label describes scientific practice and does not claim haloalkanes as required AP recall.
- case labels E, T, N, A, B, L and I
- Temporary names for the displayed structures.
- The letters are not element symbols, carbon numbers or IUPAC locants.
- Ion Y
- The displayed cyanide ion [:C≡N:]− used in the cyanide Question.
- Under the stated KCN condition, its carbon endpoint supplies the electron pair and joins the carbon skeleton.
- sigma bond
- A bond formed by electron density along the line joining two nuclei.
- Nuclei and sigma bonds remain fixed between resonance contributors.
- pi bond
- The second bond in a double bond, formed by sideways overlap.
- A neighbouring pi pair may shift in a resonance contributor.
- solvation
- Surrounding solvent molecules attract and stabilise a dissolved particle.
- Strong solvation can make an anionic nucleophile less available to attack.
- proton transfer
- A hydrogen nucleus, H+, moves from one atom to another with its bonding electrons left behind.
- After water attacks a carbocation, proton transfer converts the oxonium ion into a neutral alcohol.
Entry check 1
What must replace a one-clue pathway slogan?
Show the recovery
A local structure, condition and complete evidence audit.
Return to Concept 2.5.
1 · ObjectiveOpen
What you will understand
Build and verify complete Board and IAT-level substitution arguments across structures, evidence and conditions.
Problems this Concept unlocks
- write Board factors and distinction answers
- audit electron flow and conservation
- solve mixed mechanism evidence
- answer IAT-style integrated cases
- write supplied-data responses
- reconstruct a complete multi-step argument
2 · MysteryOpen
The problem to explain
Read these words and symbols first
- case file
- One substrate, condition set and observation set analysed together.
- Evidence from a different experiment cannot be imported silently.
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
A final case file mixes structure, conditions, electron-flow claims, rate data, an energy profile and labelled geometry.
CH3-CH2-BrDrawing the structural formula…
(CH3)3C-BrDrawing the structural formula…
Can one auditable chain explain every supplied observation and state exactly where the evidence stops?
Your decision
Build the chain before naming SN1 or SN2.
3 · InvestigationOpen
Investigation
Investigation 1
Mastery chain
Read these words and symbols first
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- mark-bearing row
- One independently scorable claim with its reason or evidence.
- Several vague claims in one paragraph do not replace separate scored rows.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
- case labels E, T, N, A, B, L and I
- Temporary names for the displayed structures.
- The letters are not element symbols, carbon numbers or IUPAC locants.
- Ion Y
- The displayed cyanide ion [:C≡N:]− used in the cyanide Question.
- Under the stated KCN condition, its carbon endpoint supplies the electron pair and joins the carbon skeleton.
- sigma bond
- A bond formed by electron density along the line joining two nuclei.
- Nuclei and sigma bonds remain fixed between resonance contributors.
- pi bond
- The second bond in a double bond, formed by sideways overlap.
- A neighbouring pi pair may shift in a resonance contributor.
- solvation
- Surrounding solvent molecules attract and stabilise a dissolved particle.
- Strong solvation can make an anionic nucleophile less available to attack.
- proton transfer
- A hydrogen nucleus, H+, moves from one atom to another with its bonding electrons left behind.
- After water attacks a carbocation, proton transfer converts the oxonium ion into a neutral alcohol.
Do
Write mastery chain as a short flow.
Check
Point to the exact evidence that supports each line.
Investigation 2
Delayed electron ledger
Read these words and symbols first
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- mark-bearing row
- One independently scorable claim with its reason or evidence.
- Several vague claims in one paragraph do not replace separate scored rows.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
- case labels E, T, N, A, B, L and I
- Temporary names for the displayed structures.
- The letters are not element symbols, carbon numbers or IUPAC locants.
- Ion Y
- The displayed cyanide ion [:C≡N:]− used in the cyanide Question.
- Under the stated KCN condition, its carbon endpoint supplies the electron pair and joins the carbon skeleton.
- sigma bond
- A bond formed by electron density along the line joining two nuclei.
- Nuclei and sigma bonds remain fixed between resonance contributors.
- pi bond
- The second bond in a double bond, formed by sideways overlap.
- A neighbouring pi pair may shift in a resonance contributor.
- solvation
- Surrounding solvent molecules attract and stabilise a dissolved particle.
- Strong solvation can make an anionic nucleophile less available to attack.
- proton transfer
- A hydrogen nucleus, H+, moves from one atom to another with its bonding electrons left behind.
- After water attacks a carbocation, proton transfer converts the oxonium ion into a neutral alcohol.
Do
Write delayed electron ledger as a short flow.
Check
Point to the exact evidence that supports each line.
Investigation 3
Evidence decision
Read these words and symbols first
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- mark-bearing row
- One independently scorable claim with its reason or evidence.
- Several vague claims in one paragraph do not replace separate scored rows.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
- case labels E, T, N, A, B, L and I
- Temporary names for the displayed structures.
- The letters are not element symbols, carbon numbers or IUPAC locants.
- Ion Y
- The displayed cyanide ion [:C≡N:]− used in the cyanide Question.
- Under the stated KCN condition, its carbon endpoint supplies the electron pair and joins the carbon skeleton.
- sigma bond
- A bond formed by electron density along the line joining two nuclei.
- Nuclei and sigma bonds remain fixed between resonance contributors.
- pi bond
- The second bond in a double bond, formed by sideways overlap.
- A neighbouring pi pair may shift in a resonance contributor.
- solvation
- Surrounding solvent molecules attract and stabilise a dissolved particle.
- Strong solvation can make an anionic nucleophile less available to attack.
- proton transfer
- A hydrogen nucleus, H+, moves from one atom to another with its bonding electrons left behind.
- After water attacks a carbocation, proton transfer converts the oxonium ion into a neutral alcohol.
Do
Write evidence decision as a short flow.
Check
Point to the exact evidence that supports each line.
Investigation 4
Condition and counter-pattern check
Read these words and symbols first
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- mark-bearing row
- One independently scorable claim with its reason or evidence.
- Several vague claims in one paragraph do not replace separate scored rows.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
- case labels E, T, N, A, B, L and I
- Temporary names for the displayed structures.
- The letters are not element symbols, carbon numbers or IUPAC locants.
- Ion Y
- The displayed cyanide ion [:C≡N:]− used in the cyanide Question.
- Under the stated KCN condition, its carbon endpoint supplies the electron pair and joins the carbon skeleton.
- sigma bond
- A bond formed by electron density along the line joining two nuclei.
- Nuclei and sigma bonds remain fixed between resonance contributors.
- pi bond
- The second bond in a double bond, formed by sideways overlap.
- A neighbouring pi pair may shift in a resonance contributor.
- solvation
- Surrounding solvent molecules attract and stabilise a dissolved particle.
- Strong solvation can make an anionic nucleophile less available to attack.
- proton transfer
- A hydrogen nucleus, H+, moves from one atom to another with its bonding electrons left behind.
- After water attacks a carbocation, proton transfer converts the oxonium ion into a neutral alcohol.
Do
Write condition and counter-pattern check as a short flow.
Check
Point to the exact evidence that supports each line.
Investigation 5
Exam answer construction
Read these words and symbols first
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- mark-bearing row
- One independently scorable claim with its reason or evidence.
- Several vague claims in one paragraph do not replace separate scored rows.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
- case labels E, T, N, A, B, L and I
- Temporary names for the displayed structures.
- The letters are not element symbols, carbon numbers or IUPAC locants.
- Ion Y
- The displayed cyanide ion [:C≡N:]− used in the cyanide Question.
- Under the stated KCN condition, its carbon endpoint supplies the electron pair and joins the carbon skeleton.
- sigma bond
- A bond formed by electron density along the line joining two nuclei.
- Nuclei and sigma bonds remain fixed between resonance contributors.
- pi bond
- The second bond in a double bond, formed by sideways overlap.
- A neighbouring pi pair may shift in a resonance contributor.
- solvation
- Surrounding solvent molecules attract and stabilise a dissolved particle.
- Strong solvation can make an anionic nucleophile less available to attack.
- proton transfer
- A hydrogen nucleus, H+, moves from one atom to another with its bonding electrons left behind.
- After water attacks a carbocation, proton transfer converts the oxonium ion into a neutral alcohol.
Do
Write exam answer construction as a short flow.
Check
Point to the exact evidence that supports each line.
Investigation 6
Independent verification
Read these words and symbols first
- audit chain
- A fixed sequence from structure through electron movement, evidence, condition, product and checks.
- A skipped link must be supplied before a mechanism verdict is accepted.
- mark-bearing row
- One independently scorable claim with its reason or evidence.
- Several vague claims in one paragraph do not replace separate scored rows.
- independent verification
- A second check that does not merely repeat the chosen method.
- Examples include atom-charge-valence audit, rate prediction, energy topology or labelled geometry.
- case labels E, T, N, A, B, L and I
- Temporary names for the displayed structures.
- The letters are not element symbols, carbon numbers or IUPAC locants.
- Ion Y
- The displayed cyanide ion [:C≡N:]− used in the cyanide Question.
- Under the stated KCN condition, its carbon endpoint supplies the electron pair and joins the carbon skeleton.
- sigma bond
- A bond formed by electron density along the line joining two nuclei.
- Nuclei and sigma bonds remain fixed between resonance contributors.
- pi bond
- The second bond in a double bond, formed by sideways overlap.
- A neighbouring pi pair may shift in a resonance contributor.
- solvation
- Surrounding solvent molecules attract and stabilise a dissolved particle.
- Strong solvation can make an anionic nucleophile less available to attack.
- proton transfer
- A hydrogen nucleus, H+, moves from one atom to another with its bonding electrons left behind.
- After water attacks a carbocation, proton transfer converts the oxonium ion into a neutral alcohol.
Do
Write independent verification as a short flow.
Check
Point to the exact evidence that supports each line.
4 · MeaningOpen
Build the meaning
Meaning 1
Mastery chain
Read structure, assign roles, move electron pairs, audit bonds and charges, compare rate-energy-geometry evidence, carry conditions, then verify independently.
Check
Point to the exact evidence that supports each line.
Meaning 2
Delayed electron ledger
Rebuild source, destination, immediate bond effect, atom count, total charge and carbon valence before naming a pathway.
Check
Point to the exact evidence that supports each line.
Meaning 3
Evidence decision
Choose SN2, SN1, insufficient evidence or conflicting evidence only after rate, energy, timing and geometry are compared.
Check
Point to the exact evidence that supports each line.
Meaning 4
Condition and counter-pattern check
Test adjacent crowding, allylic or benzylic support, nucleophile availability, leaving group and medium without treating a tendency as proof.
Check
Point to the exact evidence that supports each line.
Meaning 5
Exam answer construction
Write one mark-bearing claim on one line and attach its exact reason, condition or observation.
Check
Point to the exact evidence that supports each line.
Meaning 6
Independent verification
Check the proposed answer through a different ledger such as conservation, rate prediction, energy topology or labelled geometry.
Check
Point to the exact evidence that supports each line.
5 · ExamplesOpen
Worked examples
Example 1 of 6
Cyanide retrieval
Ion Y attacks through carbon under the stated KCN condition.
CH3-CH2-BrDrawing the structural formula…
[:C≡N:]−Drawing the structural formula…
Key evidence
- The stated KCN rule selects cyanide carbon.
- C* is the carbon that loses Br.
- The old bond must break as the new bond forms.
- A mechanism must conserve each quantity.
One lawful move at a time
One move at a time
Step 1 of 4
- Action
- Identify the donor endpoint.
- Why
- The stated KCN rule selects cyanide carbon.
- Result
- A lone pair on cyanide carbon supplies the new bond.
Answer
CH3-CH2-C≡N and Br− are formed.
Independent check
Reverse atom mapping recovers bromoethane and cyanide.
Counter-pattern
AgCN can use the nitrogen endpoint under the separately stated Board rule.
6 · QuestionsOpen
Questions
Question 1 of 14
Coordinate ambident connectivity, carbon count, electron source and conservation without a nearby worked answer.
- Specimen E reacts with ion Y through its carbon endpoint.
- Select every required statement.
CH3-CH2-BrDrawing the structural formula…
[:C≡N:]−Drawing the structural formula…
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