[Penguinone]

Rank the following in order of nucleophilicity. Justify your answers.
 PhCH2O-    HCO3-    AcO-    PhO-    CF3CO2-

Any help would be greatly appreciated!!

[Babcock_Hall]

According to forum rules, you must show your attempt before we can help you.

[Penguinone]

According to forum rules, you must show your attempt before we can help you.

Sorry I forgot, my embarrassingly bad attempt is: Least: Ph0-(as charge would be stabilized into ring), CF3CO2 (as F would be strongly electron withdrawing so would stabilize charge), HCO3 I think would be less nucleophilic than AcO- as the charge could be stabilised over the two oxygens?, then most nucleophilic PhCH2O as the charge can't be stabilised by the ring due to the CH2 group.

[spirochete]

Nucleophilicity is influenced by several factors.

1) Basicity. More basic species are more nucleophilic, all other things equal.

2) Going down the periodic table, nucleophilicity may increase with polarizability. This is especially true in protic solvents.

3) Steric hindrance. More hindered nucleophiles are less nucleophilic.

[Babcock_Hall]

@OP, What I would do next is to look up the pK_a values of the conjugate acids of these nucleophiles.

[Penguinone]

pKa values of Conjugate Acids:

CF3COOH: 0.52   H2CO3: 3.6     AcOH: 4.76    PhOH: 10.0    PhCH2OH: 15.40

So does the answer just correspond directly to these values?  ie  --> Increasing Nucleophilicity -->

[Sophia7X]

Yeah, for the most part, nucleophilicity trends follow basicity trends with some exceptions like the halide ions in water (they have an opposite trend due to significant solvation effects).

[Babcock_Hall]

When the base is bulky, then it is likely to be a poor nucleophile, for example the tertiary-butoxide ion.  I agree that solvation and polarizability are also factors.