Chemical Naming & Substance Identity

Thiamine vs Thiamin: One Substance, Two Names — Identity, Documentation and Purchasing Guide

Where each spelling is used, what it actually refers to, and how to write the order so the right material ships — for Thiamine (Vitamin B1).

Are Thiamine and Thiamin the Same Thing?

Yes. “Thiamine” is the standard trade and pharmacopoeial spelling of vitamin B1; “thiamin” is the equally valid biochemical short form. Identical CAS 59-43-8 either way.

Both names map to CAS 59-43-8 (C12H17N4OS+, 265.36 g/mol). The difference is orthographic: one spelling is the systematic or international form, the other the regional variant.

1. Name Comparison at a Glance

Attribute	Thiamine	Thiamin
Refers to	Thiamine (Vitamin B1)	Thiamine (Vitamin B1)
CAS Registry Number	59-43-8	59-43-8
Molecular formula	C12H17N4OS+	C12H17N4OS+
Molar mass	265.36 g/mol	265.36 g/mol
Typical name domain	One is IUPAC/international, the other regional	One is IUPAC/international, the other regional
Chemically different substance?	No	No
Lewis structure guide	Thiamine Lewis structure	Thiamin Lewis structure

Identical CAS, formula and molar mass on both sides is the proof of identity: the difference is purely in how the name is written.

2. Why the Two Names Exist

The difference is orthographic: one spelling is the systematic or international form, the other the regional variant.

“Thiamine” is the standard trade and pharmacopoeial spelling of vitamin B1; “thiamin” is the equally valid biochemical short form. Identical CAS 59-43-8 either way.

Dictionaries and CAS registry records often carry the US spelling, pharmacopoeias and international standards the systematic one, and older literature may use either. Neither is an error; they are the same entry searched under two orthographies.

3. Documentation and Labeling Map

Context	Term Used	What Must Be Verified
Pharmacopoeial	Thiamine hydrochloride / mononitrate	Named salt monographs define purity tests.
Literature	Thiamin	Common in enzyme and pathway papers.
Label/COA	CAS + salt form + assay	The fields that identify what was bought.

4. What Actually Differs at Purchase

Salt form (67-03-8 HCl, 619-32-9 mononitrate) drives stability, flow and dosing calculations; the spelling difference is purely orthographic.

Because the substance is identical either way, grade and documentation do the real separating: pharmacopoeial vs food vs technical grade, assay basis, impurity limits (heavy metals, residual solvents, water), container size and, for stereochemical names, an optical-purity clause.

5. Which Name Should You Use?

Write “Thiamine” when…

your market, catalog or SDS convention uses that form
the audience is US trade, procurement or customs (where Thiamine is often the registered spelling)
you keep CAS 59-43-8 next to the name on every line

Write “Thiamin” when…

the document follows IUPAC, pharmacopoeial or non-US convention
you need the fully qualified form (brand, salt or stereochemistry) on the label
search and matching must work across both spellings

Compare supply offers for Thiamine (Vitamin B1) →

6. FAQs

Are Thiamine and Thiamin chemically identical?

Yes. “Thiamine” is the standard trade and pharmacopoeial spelling of vitamin B1; “thiamin” is the equally valid biochemical short form.

Both map to CAS 59-43-8.

Which spelling is correct?

Both are accepted, but in different domains: The difference is orthographic: one spelling is the systematic or international form, the other the regional variant.

Controlled documents should use the qualified form and always add the CAS.

What should a purchase order say?

Name plus CAS plus grade plus quantity. For Thiamine (Vitamin B1) the CAS alone removes every ambiguity created by spelling, shorthand or stereochemistry prefixes.

Do different countries really use different names?

Yes — and that is precisely why the specification, not the name, decides what ships. The difference is orthographic: one spelling is the systematic or international form, the other the regional variant.

7. References

CAS registry entry for Thiamine (Vitamin B1). Identity anchor for both spellings. Dictionary page | Lewis guide
PubChem name search Cross-checks synonyms and salt forms. PubChem
USP / EP / ISO naming guidance Where the qualified name is normative. Standards overview

Editorial note

This article clarifies naming equivalence for procurement and documentation use. It is not legal or regulatory advice; the controlled source for any label is the current monograph, CAS index entry and applicable market regulations.

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Thiamine Thiamin Comparison