SME
Organic Chemistry I
Substitution and elimination
Use this for “Does 2-bromo-2-methylpropane with sodium ethoxide in ethanol substitute or eliminate, and by which path?”
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Which path does each reaction mostly take?
Tap a card, then tap its group.
Methyl and primary carbons with a good nucleophile substitute in one step; tertiary carbons form a cation unless a strong base takes a proton.
Assumptions
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Count the carbons bonded to the carbon holding the leaving group: none is methyl, one primary, two secondary, three tertiary.
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A strong base is charged and basic (HO⁻, CH₃O⁻, (CH₃)₃CO⁻); a weak one is neutral (water, an alcohol).
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Polar aprotic solvents (DMSO, acetone, DMF) speed SN2; water and alcohols hold a cation and help SN1 and E1.
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Heat favors elimination over substitution, and a bulky base takes a proton rather than reach the carbon.
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
More problem types
How the rate changes with [RX] and [Nu]
Use this for “In an SN2 reaction [RX] is halved and [Nu] is made 4 times larger. How does the rate change?”
Reading a two-step energy diagram
Use this for “Step 1 climbs 85 kJ/mol to a cation at 50 kJ/mol; step 2 climbs 15 more and ends at −30. Which step is slow, and what is ΔH?”
SN2 rate: fastest to slowest
Use this for “Rank 2-bromopropane, bromomethane and bromoethane by how fast each reacts with iodide in acetone.”