Why is the name 2-ethylbutanoic acid preferred to the name pentane-3-carboxylic acid?

Question

I used ChemSketch to find the preferred IUPAC name of this structure, according to the IUPAC 2013 rules:

Why is the name 2-ethylbutanoic acid preferred to the name pentane-3-carboxylic acid? They have the same principal group, so the same priority according to P.44.1.1 right?

P-44.1.1 The senior parent structure has the maximum number of substituents corresponding to the principal characteristic group (suffix) or senior parent hydride in accord with the seniority of classes (P-41) and the seniority of suffixes (P-43).

I would think that the rule P.44.3.2 would give the second name preference:

P-44.3.2 The principal chain has the greater number of skeletal atoms [criterion (b) in P-44.3].

Also, according to P-42.1, it seems both -carboxylic acid and -oic acid have the same seniority. If anything, carboxylic is more senior because it's placed higher in the list. There is also the rule:

P-45.2.1 the maximum number of substituent groups cited as prefixes;

Which would prefer 2-ethylbutanoic acid, but the rule P.44.3.2 is senior to this rule so that shouldn't matter.

Answer 1

I found the answer. It was not in the section P-4 of the IUPAC rules, but it was stated in the section about carboxylic acids. According to P-65.1.2.2.2 and P-65.1.2.2.1, the suffix carboxylic acid is only used when there the group is attached to a ring, or when there are more than two occurrences of the group:

P-65.1.2.2.1 If an unbranched chain is linked to more than two carboxy groups, all carboxy groups are named from the parent hydride by substitutive use of the suffix ‘carboxylic acid’, preceded by the appropriate numerical prefix ‘tri’, ‘tetra’ etc. and appropriate locants.

P-65.1.2.2.2 Carboxy groups attached to cyclic parent hydrides or heteroacyclic parent hydrides are always named by using the suffix ‘carboxylic acid’.

There are similar rules for most other characteristic groups, like P-66.6.1.1.2 and P-66.6.1.1.3 for carbaldehydes and P-66.5.1.1.3/P-66.5.1.1.2 for carbonitriles.