IB Chemistry HL 3.4.9 Hl Nucleophilic Substitution Mechanisms Questions

Use real HL exam questions to classify primary and tertiary halogenoalkanes, draw the one-step SN2 transition state, and explain the two-step SN1 carbocation pathway.

Exam points

Classify primary and tertiary halogenoalkanes and select SN2 or SN1, using substrate structure, rate dependence or solvent evidence as the justification.
Represent the one-step SN2 mechanism with nucleophile attack, leaving-group departure, partial bonds/charges in the transition state and stereochemical inversion.
Represent the two-step SN1 mechanism with ionisation to a planar carbocation followed by nucleophilic attack, including racemisation or protic-solvent stabilisation where assessed.

[Maximum number: 1]

Organic compounds have many industrial applications.

1-Bromobutane reacts with aqueous sodium hydroxide, NaOH(aq), to form butan-1-ol.

Draw the transition state produced in this mechanism.

Figure for Answer to Question IB Chemistry HL 3.4.9 Hl Nucleophilic Substitution Mechanisms Questions question 1 — IB Chemistry HL

Charge and square bracket must be included.

Accept two partial negative charges on Br AND O in HO, shown either as $\delta-$ or $\frac{1}{2-}$ .

Partial bonds from HO to C AND from C to Br must be shown.

Accept any angle for the partial bonds.

Accept carbocation, or a valid transition state, if $S_{N} 1$ named in (d)(l).

Accept any correct representation including skeletal structures.

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IB Chemistry HL 3.4.9 Hl Nucleophilic Substitution Mechanisms Questions question 1