Difficulty: Intermediate | Prerequisites: Reaction Types and Stereochemistry study notes (companion document)
These are "predict the product" practice problems covering all six named reactions: organocuprate, Suzuki, Heck, olefin metathesis, and Wittig. For each question, identify the reaction type from the reagents, then apply the stereochemistry and regiochemistry rules from the companion study notes. Try answering before reading the solution. The questions mirror common exam formats.
Q: Et₂CuLi reacts with an sp³ bromide (bromide on a secondary carbon attached to a benzene ring). What is the product?
A: The ethyl group from the cuprate replaces the bromine, forming an ethyl-substituted carbon bonded to the phenyl ring. The halide is swapped for the R group of the Gilman reagent.
Q: (CH₃)₂CuLi reacts with a trans vinyl bromide. What is the product and what is its stereochemistry?
A: The methyl group replaces the bromine. Because the reaction is stereospecific, the trans geometry of the starting vinyl bromide is preserved. The product is a trans-disubstituted alkene with the new methyl group in place of the Br.
Q: (CH₃)₂CuLi reacts with a cis vinyl bromide. What is the product and what is its stereochemistry?
A: The methyl group replaces the bromine, and the cis geometry is retained. The product is a cis-disubstituted alkene.
Q: Would an organocuprate reaction work with (CH₃)₃C-Br (tert-butyl bromide)?
A: No. Organocuprate reagents do not work with tertiary halides.
Q: A trans vinyl iodide is coupled with a phenyl boronic ester using Pd(PPh₃)₄/OH⁻. What is the product and its stereochemistry?
A: The vinyl group and the phenyl group are joined by a new C-C bond. The trans geometry of the vinyl iodide is maintained in the product. You get a trans-substituted styrene-type product.
Q: Bromobenzene reacts with a phenyl boronic ester under Suzuki conditions. What is the product?
A: Biphenyl (two phenyl rings connected by a single C-C bond). Both partners are aryl, so no alkene geometry to worry about.
Q: A cis vinyl bromide is coupled with PhB(OR)₂ under Pd(PPh₃)₄/OH⁻ conditions. What is the product?
A: The phenyl group replaces the bromine, and the cis geometry is maintained. The product is a cis-configured alkene bearing a phenyl substituent.
Q: Bromobenzene + H₂C=CH₂ with Pd(OAc)₂, PPh₃, NEt₃. What is the product?
A: Styrene (PhCH=CH₂). The phenyl group attaches to the less substituted carbon of ethylene (both are equivalent here), producing a monosubstituted alkene. Since the alkene is terminal, there is no E/Z consideration.
Q: Bromobenzene + ethyl acrylate (an alkene bearing an ester -C(=O)OEt group) under Heck conditions. What is the product and its geometry?
A: The phenyl group bonds to the less substituted end of the acrylate alkene. The product is a trans (E) cinnamate ester: Ph-CH=CH-C(=O)OEt with trans geometry across the double bond.
Q: A vinyl iodide (with an alkyl chain) + an alkene bearing a nitrile (-CN) group under Heck conditions. What is the product?
A: The vinyl group from the iodide attaches to the less substituted carbon of the nitrile-bearing alkene. The product alkene has trans geometry. The CN group remains on the more substituted carbon.
Q: A diene (with two terminal alkenes connected by a chain) is treated with Grubbs' catalyst (MLₙ). What is the product?
A: Ring-closing metathesis occurs. The two terminal alkenes react with each other to close a ring (forming a cycloalkene), and ethylene (H₂C=CH₂) is released as a byproduct. The size of the ring depends on the chain length between the two alkenes.
Q: A cycloalkene with two exocyclic alkene arms is treated with Grubbs' catalyst. What happens?
A: Ring-closing metathesis forms a smaller ring. The product is a bicyclic or a simple cycloalkane/cycloalkene, depending on the substrate, with ethylene lost.
Q: Two identical linear alkenes are treated with WCl₆/CH₃Li. What are the products?
A: Cross metathesis. The alkenes exchange partners, producing a mixture of products including a symmetrical internal alkene (the two larger fragments joined) and ethylene. Both E and Z isomers of the internal alkene are expected.
Q: A phosphonium ylide Ph₃P=C(CH₃)₂ reacts with benzaldehyde (PhCHO). What is the product?
A: The C=O of benzaldehyde is replaced by a C=C. The two methyl groups from the ylide end up on one carbon of the new alkene, and the phenyl group (plus H) from the aldehyde end up on the other. The product is a trisubstituted alkene: PhCH=C(CH₃)₂. A mixture of E/Z isomers is possible.
Q: A phosphonium ylide Ph₃P=CH(CH₃) reacts with cyclohexanone. What is the product?
A: The carbonyl oxygen of cyclohexanone is replaced by a C=C. The product is an exocyclic alkene: a cyclohexane ring with a =CHCH₃ group where the C=O used to be. Both E and Z configurations of the exocyclic alkene are possible (the H and CH₃ can be on either side).
Q: How do you identify which part of the product came from the ylide and which from the carbonyl?
A: Find the C=C in the product. One carbon of that double bond was the carbonyl carbon (it was C=O in the starting material). The other carbon, along with its substituents, came from the ylide. Triphenylphosphine oxide (Ph₃P=O) is always the byproduct.
These six reactions connect directly to earlier Orgo I material on alkene stability, E/Z naming conventions, and nucleophilic substitution. Understanding why tertiary halides fail with organocuprates ties back to steric effects covered in SN2 discussions.
The palladium-catalysed reactions (Suzuki, Heck) form the foundation for more advanced cross-coupling methods you may encounter later, such as Negishi and Sonogashira couplings. Olefin metathesis connects to polymer chemistry and macrocycle synthesis. The Wittig reaction bridges carbonyl chemistry (from Orgo I ketone/aldehyde chapters) with alkene synthesis, so it often appears as a retrosynthesis target.
Predict the product, organocuprate practice, Suzuki reaction examples, Heck reaction practice problems, carbene cyclopropanation, Simmons-Smith practice, olefin metathesis ring-closing, Grubbs' catalyst problems, Wittig reaction practice, ylide product prediction, stereochemistry drill, regiochemistry practice, Orgo II exam prep, Organic Chemistry II practice, named reactions exam, C-C bond formation problems, cross-coupling practice