Propargyl alcohol has more than a dozen names, one CAS number and no single right grade

The request from the lab says propargyl alcohol. The supplier quote says 2-propyn-1-ol, the Safety Data Sheet (SDS) says ethynylcarbinol, and the Certificate of Analysis (CoA) on the last lot said prop-2-yn-1-ol. All four describe one molecule, CAS 107-19-7, and the CAS number is the only one of the four labels that never changes. The names are a paperwork risk you can close with one cross-check. The grade is the expensive question, because a synthesis chemist and an acid-inhibitor blender need different things from the same drum.

This brief covers the molecule itself: identity on paper, what the property data means for storage and freight, and a grade specification that fits your use. How it protects steel during acidizing and pickling is a separate subject.

One molecule, more than a dozen names

Propargyl alcohol is the simplest propargylic alcohol: a hydroxyl group on one end of a three-carbon chain and a terminal alkyne on the other. The PubChem record (CID 7859) gives the formula C3H4O, a molecular weight of 56.06 g/mol and the IUPAC name prop-2-yn-1-ol. The CAS Registry Number is 107-19-7.

The synonym list is where documents stop matching. The PubChem synonym list and the catalog record carry 2-propyn-1-ol, 1-propyn-3-ol, 2-propynyl alcohol, 2-propynol, 3-propynol, propynyl alcohol, ethynylcarbinol, acetylenylcarbinol, acetylene carbinol, 1-hydroxy-2-propyne, 3-hydroxy-1-propyne and the index name methanol, ethynyl-. A CoA under one name and an SDS under another is normal. A CAS number that differs between them is not, and it is the one check worth running on every document in the file.

Four neighbors are worth checking on every quote, because each can appear under a name close enough to survive a quick read.

What does the property data mean for storage and freight?

The figures are from the PubChem record; the right-hand column is the purchasing consequence.

Start with the melting point: a dropped minus sign turns a liquid into a solid on paper. PubChem records -54 °F. A secondary property sheet that drops the minus sign and quotes the figure in Celsius describes a solid at room temperature, and a buyer who believes it will budget for drum warmers the material does not need. If a supplier sheet disagrees with PubChem on the sign of the melting point, treat every other number on that sheet as unverified until it is checked.

The flash point of 91 °F matters more day to day than the boiling point of 236.5 °F at 760 mmHg. A closed trailer or an uninsulated warehouse in a southern summer runs hotter than 91 °F, so the vapor space in a drum can hold an ignitable mixture for weeks of the year.

The flash point is one input; the hazard statements in the current SDS for the lot set the rest, from exposure controls and spill response to storage class, transport classification and transfer hardware. Read them with the safety section of the propargyl alcohol product page.

A vapor pressure of 12 mmHg is enough for drums to breathe as the temperature swings between day and night. Specify closed transfer, keep bungs tight between draws, and ask for the drum lining and closure on the quote; closed transfer limits worker exposure as well as product loss. A part-used drum that sits through a season loses product to the air and pulls in humid air in return, and the second loss is the one that shows up on the next CoA test.

PubChem lists the density as 0.9485 at 68 °F with no unit, so it cannot settle a volume-versus-weight dispute. Ask the supplier to state density with unit and temperature, or better, to quote price, minimum order and net fill by weight, which takes the arithmetic out of the dispute.

The USCG data behind that density adds a short note: less dense than water, will float. Miscibility says otherwise in practice. The liquid mixes into water instead of forming a layer that a boom and skimmer can recover, so spill and drain-isolation plans should be written for a dissolved organic, the opposite of what a floats label suggests.

One handling point follows from the chemistry itself. Propargyl alcohol is a terminal alkyne, the same functional group as acetylene, and acetylene and copper alloys are a known bad pairing. Check every wetted part in the transfer line, brass valves and fittings included, against the PubChem safety and hazards section and the current SDS before the first lot is unloaded.

Why does the right grade depend on what you do with it?

The catalog record for CAS 107-19-7 lists four uses: corrosion inhibitor for steel in hydrochloric-acid pickling and acidizing, corrosion inhibitor in well-acidizing fluids, stabilizer for chlorinated hydrocarbon formulations, and intermediate or building block in chemical synthesis. Those uses split into buyers with different tolerances, and a single grade bought for all of them serves at least one badly.

The inhibitor blender’s package is dosed into hydrochloric acid that is mostly water. Water in the incoming lot is close to irrelevant to that end use, and a trace of residual formaldehyde is unlikely to show up in inhibitor performance. What the blender needs is assay consistency from lot to lot, so the dose a formulation was qualified at delivers the same active content every time. A dry, low-formaldehyde specification on an inhibitor blend buys numbers that never reach the steel.

The synthesis buyer is reacting the triple bond or the hydroxyl, often with reagents that water destroys or that formaldehyde competes for. For that buyer, water, residual formaldehyde and butynediol are the specification, and the assay is a headline that can hide them. A lot can post a high assay and still carry enough water to consume a metal reagent or enough formaldehyde to seed a side product.

Stabilizer use in chlorinated hydrocarbons sits between the two. The additions are small, but they go into a dry organic product whose maker sets its own water limits, so water belongs on that specification as well.

How it is made sets the impurity list

Propargyl alcohol comes from Reppe chemistry: acetylene and formaldehyde react over a copper acetylide catalyst, and butynediol forms in the same process. The two are separated afterwards, which is why formaldehyde and butynediol are the impurities to name on a request for quotation (RFQ) instead of a generic other-impurities line.

The same fact shapes availability. Ask the supplier which product the plant is run for. A unit optimized for butynediol treats propargyl alcohol as the minor stream, and its output follows that plant’s schedule and its butynediol demand, not yours. A buyer with a single qualified source is exposed to a turnaround they will not hear about until the next quote is late.

What to put on the purchase order

1. Name the substance by CAS 107-19-7 and prop-2-yn-1-ol, with any synonym as a secondary label only.

2. State the end use, so the quote is for the grade that fits it and not for the most expensive one on the price list.

3. List assay, water, residual formaldehyde and butynediol, each with a test method and a limit taken from your own process.

4. Require a CoA for every lot, with lot number and test date, and reject any document whose CAS number differs from the order.

5. Request the current SDS for the grade and lot, and set storage, transfer hardware and transport classification from it.

6. Price and invoice by weight, and reconcile any volume quote on the supplier’s density, stated with unit and temperature.

Methodology: identity and property figures are taken from the PubChem record for propargyl alcohol (CID 7859), which compiles NTP (1992), USCG (1999) and NIOSH (2024) data; the four uses come from the catalog record for CAS 107-19-7. The emphasis in the specification table is the author’s judgment for each end use, not a published standard.