Supplied as a white to off-white crystalline powder, sarcosine methyl ester hydrochloride—also listed as methyl N-methylglycinate hydrochloride or methyl sarcosinate hydrochloride—is identified by CAS 13515-93-0. The linear notation CH₃NHCH₂COOCH₃·HCl corresponds to molecular formula C4H10ClNO2 and molecular weight 139.58 g/mol. Chloride ion contributes 25.4% by mass; the neutral methyl N-methylglycinate portion has molecular weight 103.12 g/mol. No harmonized ISO, DIN, or ASTM model designation is assigned to this chemical. Procurement records therefore reference CAS 13515-93-0, lot number, and specification version rather than a proprietary part number. Supplier-specific catalogue codes such as SME-HCl or SM-98 are used, but they are not interchangeable across manufacturers and must not be substituted for identity in regulatory filings.

Typical release specifications are supplier-defined because no EP, USP, or JP monograph covers this precise hydrochloride salt. A representative technical-grade acceptance profile includes assay 98.0%–101.0% on the anhydrous basis by non-aqueous potentiometric titration with 0.1 mol/L perchloric acid, water content ≤0.50% by Karl Fischer titration, residue on ignition ≤0.10% at 600 ± 25 °C, and total organic impurities ≤2.0% by HPLC area percent. The material is not a food additive and does not carry a GRAS listing under 21 CFR 170–199. For pharmaceutical intermediate applications, residual methanol is evaluated under ICH Q3C Option 2 concentrations, where the Class 2 limit is 3000 ppm. This is one regulatory distinction from the ethyl ester hydrochloride, for which ethanol is Class 3 with a default 5000 ppm.

How Does the Product Differ from Sarcosine Free Base and Ethyl Ester Hydrochloride?

The hydrochloride salt is preferred over sarcosine free base in many synthetic sequences because the salt is crystalline, free-flowing at controlled humidity below 65% RH, and easier to dose into anhydrous or aqueous reactors. Sarcosine free base is a hygroscopic solid with a strong tendency to absorb moisture; its methyl ester free base is isolated only when necessary because the neutral amino ester is more mobile and amine-volatile than the hydrochloride, and large-scale isolation data are limited. The free acid sarcosine, CAS 107-97-1, has molecular weight 89.09 g/mol and exists as a zwitterion in aqueous solution; the methyl ester hydrochloride removes the carboxylate charge and places the material into an organic-solvent-compatible form after neutralization.

Against glycine methyl ester hydrochloride, CAS 5680-79-5, molecular weight 125.55 g/mol, the N-methyl substitution adds 14.03 g/mol and eliminates one N–H hydrogen-bond donor. That difference is exploited in solution-phase peptide and peptidomimetic synthesis to install an N-methyl amide bond with reduced hydrogen-bond-mediated aggregation and altered conformational freedom. Compared with the ethyl ester hydrochloride, the methyl ester carries lower steric bulk at the ester function and is generally more reactive toward aminolysis; however, published kinetic data for this specific pair are limited, and reaction selection should be confirmed by calorimetric screening rather than assumed from ester class alone. In procurement, the methyl ester hydrochloride is selected when the downstream route requires a protected carboxyl group during N-functionalization. The free acid sarcosine is selected when the carboxylate itself participates directly in acylation, as in the manufacture of N-acyl sarcosinate surfactants. The ethyl ester hydrochloride may be preferred when residual methanol is undesirable or when the route will later transesterify to a higher alcohol.

On production-scale drying equipment, residual solvent and moisture endpoints are not controlled by fixed time. In a 2 m² agitated vacuum dryer operated at 40 °C and 15 kPa, residual methanol removal decreases when the wet cake is loaded above 15 cm depth because the upper and lower cake regions reach endpoint at different rates. Intermediate lump breaking and bed inversion are used; endpoint is confirmed by Karl Fischer titration and static headspace GC rather than by drying time alone. For materials entering moisture-sensitive coupling reactions, pre-drying is required if water content exceeds 0.50% or if the storage environment has exceeded 60% RH during handling.

Elemental impurities are not universally specified for technical grade, but pharmaceutical intermediate buyers may request a report against USP <232>/<233>. If the material is returned to a continuous feeder or solid-phase reactor, particle-size distribution may be controlled by sieve analysis per ISO 3310-1; no harmonized particle-size specification exists for this salt. For pharmaceutical intermediate supply chains, vendor qualification under ICH Q7 should include review of process validation data, cleaning validation limits, and storage stability data. Analytical method transfers should follow ICH Q2(R1) for assay and related-substance procedures, and residual solvent method validation should cover methanol in the presence of dichloromethane or tetrahydrofuran if those solvents are used upstream.

When the Hydrochloride Salt Is Preferred for Anhydrous Coupling and Selective N-Acylation

In Schotten-Baumann acylation, the salt is charged to a jacketed reactor, suspended in water or aqueous tetrahydrofuran, and cooled to 0–5 °C. Sodium bicarbonate or 20% w/w aqueous sodium hydroxide is metered to maintain a pH window of 8.5–9.5. Acid chloride is then added over 2–4 h under Rushton-turbine agitation at 250–350 rpm. If the pH falls below 7.5, the concentration of free amino ester drops and acylation stalls; if the pH exceeds 10.5, the methyl ester hydrolyzes and the yield of the desired N-acyl derivative falls. Saturated bicarbonate is preferred over concentrated sodium hydroxide when minimizing ester hydrolysis is critical because it buffers near the lower end of the operating window.

In kilogram-scale batches, a significant processing bottleneck occurs when the hydrochloride is neutralized too quickly and the liberated amino ester partitions into the organic phase before the acid chloride feed has been initiated. This produces a transient pH excursion and variable conversion across lots. Production campaigns mitigate this by delaying the acylating agent until the aqueous phase is buffered, and by verifying a stable pH for at least 15 min before feed start. If pH oscillation exceeds ±0.3 pH units, the feed is paused and the jacket is held at 2 °C until control returns.

For anhydrous couplings, the hydrochloride is suspended in dichloromethane or dimethylformamide and treated with one equivalent of N-methylmorpholine at 0 °C. The resulting N-methylmorpholine hydrochloride precipitate is removed by filtration, and the free methyl N-methylglycinate is carried forward immediately without isolation. Coupling reagents such as HATU or EDC with an additive are then used under standard amide-forming conditions; reaction progress is followed by HPLC with UV detection at 210–220 nm. This in situ release route avoids the handling losses and amber discoloration that can accompany storage of the free amino ester.

The secondary amine functional group imposes a nitrosation control boundary. Acidic process streams containing this compound must not be exposed to sodium nitrite, nitrite-bearing reagents, or high-oxide nitrogen species without a documented nitrosamine risk assessment under ICH M7. Published acceptable intake data for N-nitrososarcosine methyl ester are limited; until toxicology-derived limits are available, conservative class-specific default controls and purge calculations are applied. For drug-substance intermediates, nitrosamine risk should be addressed before scale-up, and analytical methods should be validated to detect the specific N-nitroso derivative at a limit of quantification appropriate to the proposed acceptable intake.

The hydrochloride is incompatible with strong bases, strong oxidizing agents, and unneutralized acid chlorides. Contact with strong base releases the free amino ester and methanol; this should be anticipated during wastewater neutralization and equipment cleaning. The product is not marketed as a formulated end-use ingredient. REACH registration status and any specific authorization or restriction requirements must be confirmed with the supplier under the latest EINECS/ELINCS listing, and RoHS obligations do not apply to the neat chemical unless it is incorporated into an electrical or electronic article.

Storage Boundaries, Incompatibility Limits, and Bulk Handling Controls

Bulk storage should be in tightly closed containers under dry nitrogen at 15–25 °C and relative humidity not exceeding 65% RH. In climates where warehouse humidity exceeds 60% RH for prolonged periods, transfer should be completed in a humidity-controlled room or the material should be pre-dried immediately before use. Opened containers are re-sealed under nitrogen after each withdrawal because the salt can cake and form hard lumps upon moisture uptake. Vacuum drying, when required, is performed below 40 °C and at 10–15 kPa; drying above 60 °C should be justified by differential scanning calorimetry because published thermal stability data for this specific salt are limited.

Shelf life is supplier-specific and must be taken from the certificate of analysis; a common retest interval is 24 months when the storage conditions above are maintained, but this is not a harmonized standard. Standard packaging is a 25 kg net fiber drum with a low-density polyethylene liner under nitrogen. After receiving, appearance, water content, and identity should be rechecked for any container that shows liner damage or water contact.