[ { "name": "IChO-2025_1", "background": { "image": "images/1/1_bg.png", "context": "Sesquiterpenes have the formula C_{15}H_{24}. They are secondary metabolites in plants and both deter insects which eat plants and attract animals which eat the insects. Isocaryophyllene (i-Cy) is a sesquiterpene found in oregano, rosemary, pepper, and cloves. The structural formula of i-Cy can be determined by performing various reactions and analysing the products as shown in the figure." }, "points": 34 }, { "name": "IChO-2025_1.1", "modality": "image + text", "type": "Structure Construction", "evaluation": "Structure Match", "requirement": "", "points": 7, "field": "", "source": "IChO-2025", "question": { "context": "Draw the structures of i-Cy, A, and B.", "image": "images/1/1.1_ques.png", "requirement": "Convert the drawn structures to SMILES format (stereochemistry not required).", "parsing_note": "The reaction diagram has been converted to reaction_scheme.", "reaction_scheme": [ { "reactant_name": "i-Cy", "reactant_formula": "C_{15}H_{24}", "conditions": "H_{2}, Pd/C", "product_name": "B", "product_formula": "C_{15}H_{28}" }, { "reactant_name": "i-Cy", "reactant_formula": "C_{15}H_{24}", "conditions": "(1) BH_{3}/THF (1/3 equiv.), THF ; (2) H_{2}O_{2}, NaOH, H_{2}O", "product_name": "A", "product_formula": "C_{15}H_{26}O" }, { "reactant_name": "i-Cy", "reactant_formula": "C_{15}H_{24}", "conditions": "(1) O_{3}, CH_{2}Cl_{2}; (2) Zn, CH_{3}COOH", "product_smiles": [ "C=O", "CC1([C@]([H])(CCC(C)=O)[C@@](C(CCC([H])=O)=O)(C1)[H])C" ] }, { "reactant_name": "A", "reactant_formula": "C_{15}H_{26}O", "conditions": "(1) O_{3}, CH_{2}Cl_{2}; (2) Zn, CH_{3}COOH", "product_name": "C", "product_smiles": "CC1(C)[C@]([C@@]([H])([C@](CO)(CCC([H])=O)[H])C1)([H])CCC(C)=O" } ] }, "answer": [ { "name": "A", "image": "images/1/1.1_ans_A.png", "smiles": "CC1=CCC[C@@H](CO)[C@]2([H])[C@]([H])(C(C)(C)C2)CC1", "alternative_smiles": "CC1=CCCC(CO)C2([H])C([H])(C(C)(C)C2)CC1", "points": 2, "grading": { "partial_credit": [ { "condition": "if missing a carbon atom in the ring or added another carbon atom in the ring.", "deduction": -1 } ], "notes": "Stereochemistry will not be marked for A." } }, { "name": "B", "image": "images/1/1.1_ans_B.png", "smiles": "CC1CC[C@@]([H])(C(C)(C)C2)[C@@]2([H])C(C)CCC1", "alternative_smiles": "CC1CCC([H])(C(C)(C)C2)C2([H])C(C)CCC1", "points": 2, "grading": { "partial_credit": [ { "condition": "If the structure is incorrect, but consistent with isocaryophyllene (and 2 equivalents of $H_2$ are added).", "deduction": 0 } ], "notes": "Also 2 pt Stereochemistry will not be marked for B." } }, { "name": "i-Cy", "image": "images/1/1.1_ans_i-Cy.png", "smiles": "C/C(CC[C@]1([H])[C@]2([H])CC1(C)C)=C/CCC2=C", "alternative_smiles": "C/C(CCC1([H])C2([H])CC1(C)C)=C/CCC2=C", "points": 3, "grading": { "partial_credit": [ { "condition": "If missing a carbon atom or added another carbon atom in the ring.", "deduction": -1 }, { "condition": "If a ring is made by combining two other C atoms and added a methyl to the other carbon", "deduction": -1 }, { "condition": "If no second ring is present; only added CH3 to all/one/two carbonyls in the right-hand structure.", "deduction": -2 } ], "notes": "The trans-isomer gets full marks. Stereochemistry will not be marked for i-Cy." } } ] }, { "name": "IChO-2025_1.2", "modality": "image + text", "type": "Qualitative Identification", "evaluation": "Selection Check", "points": 3, "field": "", "source": "IChO-2025", "question": { "context": "Circle the stereocentres in compound C and assign them as R or S.", "image": "images/1/1.2_ques.png", "parsing_note": "The structure in the image has been converted to SMILES format.", "smiles": "[H][C@@]1(C(C)(C)C[C@]1([H])[C@@](CCC([H])=O)(CO)[H])CCC(C)=O", "requirement": "1) Count only carbon atoms (C) in the SMILES string from left to right, ignoring all other atoms like H, O, N. Number each carbon sequentially as C-1, C-2, C-3, etc. 2) Assign R or S configuration to each. Output format: 'C-X: R/S'." }, "answer": { "context": "C-1: R, C-6: S, C-7: R", "image": "images/1/1.2_ans.png", "grading": { "partial_credit": [ { "condition": "Each centre not correctly circled", "deduction": -1 }, { "condition": "Each descriptor not correct", "deduction": -0.5 }, { "condition": "Each incorrect centre is circled.", "deduction": -1 } ], "notes": "Minimum score is 0" }, "points": 3 } }, { "name": "IChO-2025_1.3", "modality": "image + text", "type": "Structure Construction", "evaluation": "Structure Match", "points": 6, "field": "", "source": "IChO-2025", "question": { "context": "Clovene (Cv) can be synthesised from i-Cy under acid catalysis. The synthesis of Cv starts from compound D. Draw the structures of compounds E and F.", "image": "images/1/1.3_ques.png", "parsing_note": "The reaction diagram has been converted to reaction_scheme.", "requirement": "Convert the drawn structures to SMILES format (stereochemistry not required).", "reaction_scheme": [ { "reactant_name": "D", "reactant_smiles": "C[C@@]1(CCC2)C=CC(O)[C@@]2(CC(OC)=O)C1", "conditions": "H^{+} (cat.)", "product_name": "E", "product_formula": "C_{12}H_{16}O_{2}" }, { "reactant_name": "E", "reactant_formula": "C_{12}H_{16}O_{2}", "conditions": "1) LiAlH_{4}, Et_{2}O; 2) H^{+}, H_{2}O", "product_name": "F" }, { "reactant_name": "F", "step_name": "1", "product_name": "G", "product_smiles": "C[C@]1(C=C2)CCC[C@](CCO)(C1)C2=O" }, { "reactant_name": "G", "reactant_smiles": "C[C@]1(C=C2)CCC[C@](CCO)(C1)C2=O", "step_name": "2", "product_name": "H", "product_smiles": "C[C@]1(C=C2)CCC[C@](CC(O)=O)(C1)C2=O" } ] }, "answer": [ { "name": "E", "image": "images/1/1.3_ans_E.png", "smiles": "O=C1C[C@@]23C[C@@](CCC3)(C)C=C[C@H]2O1", "alternative_smiles": "O=C1CC23CC(CCC3)(C)C=CC2O1", "points": 3, "grading": { "partial_credit": [ { "condition": "If the structure is not cyclic and only the ester is removed.", "deduction": -2 } ], "notes": "Stereochemistry will not be marked." } }, { "name": "F", "image": "images/1/1.3_ans_F.png", "smiles": "O[C@H]1[C@@]2(CCO)C[C@@](CCC2)(C)C=C1", "alternative_smiles": "OC1C2(CCO)CC(CCC2)(C)C=C1", "points": 3, "grading": { "partial_credit": [ { "condition": "If reducing the ester to an aldehyde (and alcohol).", "deduction": -2 } ], "notes": "Stereochemistry will not be marked." } } ] }, { "name": "IChO-2025_1.4-5", "modality": "image + text", "type": "Qualitative Identification", "evaluation": "Selection Check", "points": 2, "field": "", "source": "IChO-2025", "question": { "context": "Clovene (Cv) can be synthesised from i-Cy under acid catalysis. The synthesis of Cv starts from compound D. For steps '1' and '2' several reagents could be considered. For example: A. PCC B. K_{2}Cr_{2}O_{7}, H_{2}SO_{4}, H_{2}O C. MnO_{2} D. (i) OsO_{4} , (ii) KHSO_{3} From the reagents above, tick which one(s) would be suitable for step '1'. From the reagents above, tick which one(s) would be suitable for step '2'.", "image": "images/1/1.4-5_ques.png", "parsing_note": "The structure in the image has been converted to SMILES format.", "smiles": { "name": "PCC", "components": [ "c1cc[nH+]cc1", "[O-][Cr](Cl)(=O)=O" ] }, "requirement": "Convert the drawn structures to SMILES format (stereochemistry not required)." }, "answer": [ { "name": "step 1", "choice": "C", "points": 1 }, { "name": "step 2", "choice": "B", "points": 1 } ] }, { "name": "IChO-2025_1.6", "modality": "image + text", "type": "Structure Construction", "evaluation": "Structure Match", "points": 8, "field": "", "source": "IChO-2025", "question": { "context": "Draw the structures of compounds I, J, and K.", "image": "images/1/1.6_ques.png", "parsing_note": "The reaction diagram has been converted to reaction_scheme.", "requirement": "Convert the drawn structures to SMILES format (stereochemistry not required).", "reaction_scheme": [ { "reactant_name": "H", "reactant_smiles": "C[C@]1(C=C2)CCC[C@](CC(O)=O)(C1)C2=O", "conditions": "1) H_{2}, Pd/C; 2) CH_{3}OH H^{+}", "product_name": "I" }, { "reactant_name": "I", "conditions": "1) HOCH_{2}CH_{2}OH, H^{+}; 2) NaOH, H_{2}O", "product_name": "J" }, { "reactant_name": "J", "conditions": "1) SOCl_{2}; 2) Et_{2}CuLi; 3) H^{+}, H_{2}O", "product_name": "K" }, { "reactant_name": "K", "conditions": "1) NaOH, H_{2}O, Δ", "intermediate_smiles": "CC1=C2CC[C@]3(CCC[C@]2(CC1=O)C3)C", "product_name": "Cv", "product_smiles": "CC1([C@@]2(CC[C@]3(CCC[C@]2(C=C1)C3)C)[H])C" } ] }, "answer": [ { "name": "I", "image": "images/1/1.6_ans_I.png", "smiles": "O=C1C=C[C@]2(CCC[C@]1(CC(OC)=O)C2)C", "alternative_smiles": "O=C1C=CC2(CCCC1(CC(OC)=O)C2)C", "points": 3, "grading": { "partial_credit": [ { "condition": "if double bond is not reduced.", "deduction": -2 }, { "condition": "if ester is not formed", "deduction": -1 } ], "notes": "Stereochemistry will not be marked for I. Minimum score is 0 pt." } }, { "name": "J", "image": "images/1/1.6_ans_J.png", "smiles": "CC1CC[C@@]([H])(C(C)(C)C2)[C@@]2([H])C(C)CCC1", "alternative_smiles": "CC1CCC([H])(C(C)(C)C2)C2([H])C(C)CCC1", "points": 2, "grading": { "partial_credit": [ { "condition": "if acetal group is incorrect/not present.", "deduction": -1 }, { "condition": "if original ester is still present; protective group is in place.", "deduction": -1 }, { "condition": "if ester is formed with ethylene glycol.", "deduction": -1.5 } ], "notes": "Stereochemistry will not be marked for I. Minimum score is 0 pt." } }, { "name": "K", "image": "images/1/1.6_ans_K.png", "smiles": "O=C1C=C[C@]2(CCC[C@]1(CC(CC)=O)C2)C", "alternative_smiles": "O=C1C=CC2(CCCC1(CC(CC)=O)C2)C", "points": 3, "grading": { "partial_credit": [ { "condition": "If acetal protecting group is still present.", "deduction": -1 }, { "condition": "If acid is turned into acid chloride and protective group is removed.", "deduction": -2 }, { "condition": "If five-membered ring is already formed with an alcohol group still present.", "deduction": -2 } ], "notes": "Stereochemistry will not be marked for I. Minimum score is 0 pt." } } ] }, { "name": "IChO-2025_1.7-8", "modality": "image + text", "type": "Structure Construction", "evaluation": "Structure Match", "points": 4, "field": "", "source": "IChO-2025", "question": { "context": "Humulene (Hu) is another sesquiterpene. It can be converted to α-caryophyllene alcohol (α-Ca), which is similar in structure to Cv. This conversion is an acid-catalysed hydration reaction which takes place via multiple intermediate structures. Incomplete structures of some intermediates, X and Y, are shown. The transformation from Hu to X is an acid-catalysed isomerisation reaction. Intermediate Y is charged.", "image": "images/1/1.7-8_ques.png", "parsing_note": "The reaction diagram has been converted to reaction_scheme.", "requirement": "Convert the completed structures to SMILES format.", "reaction_scheme": [ { "reactant_name": "Hu", "reactant_smiles": "CC1(C)C/C=C(C)/CC/C=C(C)/C/C=C/1", "conditions": "H^{+} (cat.)", "product_name": "X", "product_smiles": "CC1CCC(C)(C)CCC(C)CCC1" }, { "reactant_name": "X", "reactant_smiles": "CC1CCC(C)(C)CCC(C)CCC1", "conditions": "+H^{+}", "product_name": "Y", "product_smiles": "CC1(CC2C3(C)CCCC(C)C3C2C1)C" }, { "reactant_name": "Y", "reactant_smiles": "CC1(CC2C3(C)CCCC(C)C3C2C1)C", "conditions": "1) H_{2}O, -H^{+}", "product_name": "α-Ca", "product_smiles": "CC1(C)CC(C2C1)C3(CCCC2(C3O)C)C" } ] }, "answer": [ { "name": "X", "image": "images/1/1.7-8_ans_X.png", "smiles": "CC1=C\\CC/C(C)=C/CC(C)(C)C/C=C/1", "alternative_smiles": "C/C1=C/C=C/C(C)(C)C/C=C(C)/CCC1", "points": 2, "grading": { "partial_credit": [ { "condition": "for each mistake down to zero.", "deduction": -1 }, { "condition": "if all double bonds are mirrored.", "deduction": -1 } ] } }, { "name": "Y", "image": "images/1/1.7-8_ans_Y.png", "smiles": "CC1(C)CC2C3(CCC[C+](C3C2C1)C)C", "points": 2, "grading": { "partial_credit": [ { "condition": "if any other charge or group has been added to the structure.", "deduction": -2 } ] } } ] }, { "name": "IChO-2025_1.9", "modality": "image + text", "type": "Qualitative Identification", "evaluation": "Selection Check", "points": 2, "field": "", "source": "IChO-2025", "question": { "context": "Five carbon atoms are circled in Hu. Through understanding the mechanism we can determine where these five carbon atoms end up in α-Ca. Circle the five corresponding carbon atoms in α-Ca which are circled in Hu.", "image": [ { "Hu": "images/1/1.9_ques_Hu.png" }, { "Y": "images/1/1.9_ques_α-Ca.png" } ], "smiles": { "Hu": "CC1(C)CC/C=C(C)/CC/C=C(C)/C/C=C/1", "Y": "CC1(CC(C2(C)CCCC3(C)C2O)C3C1)C" }, "parsing_note": "The structure in the image has been converted to SMILES format.", "requirement": "1) Count only carbon atoms (C) in the SMILES string from left to right, ignoring all other atoms like H, O, N. Number each carbon sequentially as C-1, C-2, C-3, etc. 2) In Hu, C-6, C-7, C-12, C-14, C-15 are circled based on Hu smiles. 2) Give the five corresponding carbon atoms in α-Ca which are circled in Hu, Output format: 'C-X, C-X'." }, "answer": { "context": "C-5, C-6, C-8, C-12, C-13", "image": "images/1/1.9_ans.png", "grading": { "partial_credit": [ { "condition": "if five circles are correct.", "deduction": 0 }, { "condition": "if four circles are correct and one incorrect or missing.", "deduction": -1 }, { "condition": "for more than five carbons circled or two or more incorrect/missing.", "deduction": -2 } ], "notes": "Minimum score is 0" }, "points": 2 } } ]