Question: What is a good setting for running a transition state (saddle point) using PYSCF?

from pyscf import optimize; optimize(mf,method=’ts’)

Answer: C

Explanation: setting {'transition': True} will run transition state optimization.


Question: Which of the following command will result in the best accuracy when computing the enthalpy of formation for a wide range of molecules (regardless of cost).

# B3LYP/GTBas3 Opt=(VeryTight) Freq=(VibRot) Int=UltraFine SCF=QC

# M06-2X/def2-QZVPP Opt Freq Int=UltraFine

Answer: B

Explanation: Composite method is more suitable for enthalpy of formation calculation.


Question: I am trying to use Gaussan16 to search for a transition state with geometries of reactant (R) and product (P), what is the best solution

# B3LYP/6-31G* OPT=(TS) … with (R+P)/2 as geometry input

# B3LYP/6-31G* OPT=(QST3) … with R, P, (R+P)/2 as geometry input

# B3LYP/6-31G* OPT=(QST2) … with R and P as geometry input

A good enough TS initial guess is required before running optimization.

Answer: C

Explanation: (R+P)/2 is not a good initial guess, so the better way is to directly use QST2


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of COC1=CC=CC(CC2=CC([N+]([O-])=O)=CC(OC(N(CC)C(C)C)=O)=C2)=C1?

Answer: A


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of O=C(NCC1=CC=CC=C1C(OCC)=O)C2CNCC(CCSC)C2?

Answer: C


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of COCC1=NN=C(C2=CC=C(C(OC(C)C)=O)C=C2)N=N1?

Answer: A


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of OCCCC1=CN(C(OC(C)(C)C)=O)C2=C(Br)C=C(CC3=CC(C(C)=O)=CC(C)=C3)C=C21?

Answer: A


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of COC(=O)N1CCN(c2ccc3cc(-c4ccncc4C(=O)C=C)cc3[nH]c5ccccc5C)CC1?

Answer: B


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of O=C(N(CC)C(C)C)OC1=C(C2=CC(N3CCOCC3)=CC=N2)C(CC4=C(C5=CC=CS5)C=CC=C4)=CC([N+]([O-])=O)=C1?

Answer: A


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of O=C(NCC1=CC=C(C2=CN=CN=C2)C=C1C(OCC)=O)C3CN(C4=CC(O)=CC=C4)CC(CCS(N)(=O)=O)C3?

Answer: C


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of O=C(OCN1=CC=NC=C1)CC2=NN=C(C)N=N2?

Answer: B


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of CC(C1=CC(C)=CC(CC2=CC(Br)=C3C(C(C4=CNC5=C4C=C(CCC(O)=O)C=C5)=CN3C(OC(C)(C)C)=O)=C2)=C1)=O?

Answer: B


Question: Which of the following molecular weights could be the mass of a fragment peak of the given SMILES of BrC1=NC(NCCO)=CC(SC2=CC=C(NC(C=C)=O)C=C2)=C1?

Answer: A


Question: You are an organic chemist working on the following reaction, O=C(C1=CC=CC=C1)N>>NCC2=CC=CC=C2. Assuming there is a functional group on the benzene ring during this hydrogenation reaction, which of the following option needs extra protection?

Answer: D

Explanation: Lead to Alchohol


Question: You are an organic chemist working on the following reaction, CC(C)(Br)C1=CC=CC=C1.O>>CC(C)(O)C2=CC=CC=C2. Assuming there is a functional group on the benzene ring during this reaction, which of the following option will lead to side reactions?

Answer: B

Explanation: Nitro is weak neutrophilic


Question: You are an organic chemist working on the following reaction, OC1=CC=CC=C1.O=C(C2=CC=CC=C2)O>>O=C(C3=CC=CC=C3)OC4=CC=CC=C4. Assuming there is a functional group on phenol during this reaction, which of the following option needs extra protection?

Answer: B

Explanation: Lead to Thiol


Question: You are an organic chemist working on the following reaction, C=CC=C.C=CC(OCC)=O>>O=C(C1CCCCC1)OCC. Assuming there is a functional group on ethyl acrylate during this reaction, which of the following option needs extra protection?

Answer: D

Explanation: Alkyne may participate to DA reaction


Question: You are an organic chemist working on the following reaction, OCC1=CC=CC=C1.O=S(Cl)Cl>>ClCC2=CC=CC=C2. Assuming there is a functional group on ethyl acrylate during this reaction, which of the following option needs extra protection?

Answer: A

Explanation: Lead to Acyl chloride


Question: You are an organic chemist working on the following reaction, O=C(C1=CC=CC=C1)OCC>>OCC2=CC=CC=C2. Assuming there is a functional group on ethyl acrylate during this reaction, which of the following option needs extra protection?

Answer: D


Question: You are an organic chemist working on the following reaction, C(CCC)=O>O=[Mn](=O)(=O)([K])=O>OC(CCC)=O. Assuming there is a functional group on butyraldehyde during this reaction, which of the following option does not need extra protection?

Answer: D

Explanation: KMnO4 is very oxidative. Thus only Ester can be compatible


Question: You are an organic chemist working on the following reaction, OCC1=CC=CC=C1.CC(O)=O>>CC(OCC2=CC=CC=C2)=O. Assuming there is a functional group on the benzene ring during this reaction, which of the following option needs extra protection?

Answer: A

Explanation: Amide will be formed.


Question: You are an organic chemist working on the following reaction, OCC1=CC=CC=C1>>OC(C2=CC=CC=C2)=O. Assuming there is a functional group on the benzene ring during this reaction, which of the following option needs extra protection?

Answer: C

Explanation: aldehyde can be oxidized very easily


Question: You are an organic chemist working on the following reaction, BrC1=CC=CC=C1.OB(C2=CC=CC=C2)O>>C3(C4=CC=CC=C4)=CC=CC=C3. Assuming there is a functional group on the benzyl bromide during this Pd-catalyzed reaction, which of the following option needs extra protection?

Answer: C

Explanation: buchwald-hartwig may occur