Final answer:
The prefix 'proto-' in chemical nomenclature does not always consistently indicate the first in a series and its application can vary based on structural or historical considerations. 'Proto-' is not standard for indicating a primary stereoisomer, and naming conventions, as outlined by the IUPAC, have evolved to more systematic methods with numbers as infixes.
Step-by-step explanation:
The prefix 'proto-' in chemical nomenclature often indicates an important aspect of the compound's structure or historical discovery. In the case of protocatechuic acid, there might not be a compound named 'catechuic acid' without the prefix 'proto-', but the naming could reflect historical aspects or structural relationships to other compounds.
There's no indication that the prefix 'proto-' is uniformly applied to designate a stereoisomer as the original or primary form, which is confirmed by the fact that other stereoisomers, such as (−)-gala-quercitol, do not follow this pattern.
The broader usage of 'proto-' can vary significantly based on the compound characteristics or history, and may not always denote the first in a series. This is different from other systematic naming conventions, such as the recent IUPAC guidelines that advise placing numbers to indicate specific positions within a compound as an 'infix' (e.g., propan-2-ol rather than 2-propanol). Similarly, common names in chemistry, such as formaldehyde and acetaldehyde, can vary from their systematic names, which reflect the structure more directly, like methanal and ethanal, respectively.
To gain definitive insights into the current nomenclature, one would have to consult with chemical nomenclature experts or reference the latest IUPAC guidelines to understand if the names like 'protocatechuic acid' and '(+)-proto-quercitol' are in alignment with established norms.