Strongest nucleophile isRNH2ROHC6H5O−CH3O−

The question seems to be asking which of the given compounds is the strongest nucleophile. The compounds given are RNH2, ROH, C6H5O−, and CH3O−.

Nucleophilicity is the measure of a species' ability to donate an electron pair to an electrophile. It is influenced by charge, electronegativity, steric hindrance, and the solvent.

1. RNH2: This is a primary amine. Amines are generally good nucleophiles because nitrogen has a lone pair of electrons it can donate. However, it is not negatively charged, so it is not as strong a nucleophile as some other species.

2. ROH: This is an alcohol. Alcohols are not very good nucleophiles because the oxygen atom is quite electronegative and holds onto its lone pair of electrons tightly.

3. C6H5O−: This is a phenoxide ion. The negative charge on the oxygen makes it a strong nucleophile. However, the resonance stabilization of the phenoxide ion decreases its nucleophilicity because the negative charge is delocalized over the entire phenyl ring.

4. CH3O−: This is a methoxide ion. Like the phenoxide ion, it has a negative charge on the oxygen, making it a strong nucleophile. However, unlike the phenoxide ion, it does not have resonance stabilization, so the negative charge is localized on the oxygen.

Therefore, out of the given options, CH3O− (methoxide ion) is