Does MPEG-350 have an exact molecular weight of 350?

No. MPEG-350 is a monomethyl ether polyethylene-glycol distribution with a nominal average molecular weight near 350. Confirm the molecular-weight range, hydroxyl value, water, color, viscosity, and functional requirements of the offered grade; these are more useful for comparison than the nominal label alone.

Does CAS 9004-74-4 prove that an industrial MPEG-350 grade meets NF or Ph. Eur. requirements?

No. Industrial and compendial MPEG-350 grades can share the same CAS. Pharmacopoeial suitability requires the exact grade, current monograph claim, manufacturing controls and supporting documents. State the regulated application and required standard before requesting a specification, COA, TDS and SDS.

Methoxy Polyethylene Glycol 350 (MPEG-350) CAS 9004-74-4

MPEG-350 (CAS 9004-74-4), also called Poly(ethylene glycol) methyl ether or Methoxy PEG, is a monomethyl-ether polyethylene glycol with a nominal average molecular weight near 350. It is used as a chemical intermediate, solvent, carrier and formulation component. Confirm average molecular weight, hydroxyl value, water, color and viscosity against the current COA, TDS and SDS.

CAS: 9004-74-4
Synonyms: Poly(ethylene glycol) methyl ether, mPEG 350, Methoxy PEG, Polyethylene Glycol Monomethyl Ether, Methyl Polyglycol, Methoxypolyethylene Glycol Ether
Einecs: 618-394-3 (ECHA List)
Molecular Formula: CH₃O(CH₂CH₂O)ₙH (average Mn ≈ 350)
Grade: Specified by average molecular weight or hydroxyl range, water, viscosity, color, acidity or pH and physical form; see the current TDS and COA.
Package: Drums or bulk; confirm container, liner, net weight and handling for your order and destination.

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Product Description

1 Identity and physicochemical profile

2 Applications and grade selection

3 Storage and handling

4 Safety, documentation and procurement

Identity and physicochemical profile

Item	Technical guidance
Product identity	Methoxy Polyethylene Glycol 350 (MPEG-350); polyethylene glycol monomethyl ether
CAS / EC	9004-74-4 / 618-394-3 (ECHA List)
Nominal formula	CH₃O(CH₂CH₂O)ₙH, with a molecular-weight distribution centered near average Mn 350
Functionality	Nominally monofunctional with one terminal hydroxyl group; residual or distribution-related components depend on the supplied grade
Key quality controls	Average molecular weight, hydroxyl value, water, viscosity at a stated temperature, color, acidity or pH and appearance

Applications and grade selection

MPEG-350 is evaluated as a reactive intermediate for esters and other derivatives, and as a polar solvent, carrier, humectant or lubricity component in technical formulations.

For synthesis, use hydroxyl value and water to calculate charge and monitor reaction conversion; nominal molecular weight alone is insufficient.
Do not substitute PEG-400 directly: PEG is nominally difunctional, whereas MPEG has a methyl end cap and one terminal hydroxyl group.
Compare viscosity, water, color and downstream reaction or formulation performance before approving a new source.

Storage and handling

MPEG-350 is moisture-sensitive in many applications. Keep packages tightly closed, limit humid-air exposure and follow the current TDS and SDS for storage temperature, transfer and any blanketing requirement.

Safety, documentation and procurement

Use the exact SDS for PPE, spill control, transport and disposal. A purchase specification should state average molecular weight or hydroxyl range, water, viscosity method and temperature, color, application, package, quantity, destination and required COA, TDS and SDS.

For adjacent PEG and PEG-ester pages, review Polyethylene Glycol 300 and PEG Monooleate.

FAQ - Technical & Supply Chain

Q:
Does MPEG-350 have an exact molecular weight of 350?

A: No. MPEG-350 is a monomethyl ether polyethylene-glycol distribution with a nominal average molecular weight near 350. Confirm the molecular-weight range, hydroxyl value, water, color, viscosity, and functional requirements of the offered grade; these are more useful for comparison than the nominal label alone.
Q:
Does CAS 9004-74-4 prove that an industrial MPEG-350 grade meets NF or Ph. Eur. requirements?

A: No. Industrial and compendial MPEG-350 grades can share the same CAS. Pharmacopoeial suitability requires the exact grade, current monograph claim, manufacturing controls and supporting documents. State the regulated application and required standard before requesting a specification, COA, TDS and SDS.

Ordering & Documentation

Key information for document requests, quotations, and supply planning.

Documents

COA, TDS, SDS/MSDS and packing details are available on request.

Quotation

Send the CAS number, grade, quantity, packing preference and destination.

Sample & Supply

Support is available for samples, trial orders, bulk and repeat supply.

Storage & Shipping

Product-specific conditions are confirmed before order.

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