Free malondialdehyde (MDA, CH2(CHO)2) is a C3 dialdehyde that polymerizes in hours at room temperature, stains every nucleophile it touches, and is genotoxic enough to be the canonical lipid-peroxidation biomarker nobody wants on a bench. Yet drug-discovery chemists need MDA's exact carbon skeleton to close pyrimidines, pyrazoles, and pyridazines every week. The industry workaround is not to store MDA at all—it is to ship its fully acetal-protected twin, 1,1,3,3-tetramethoxypropane, where the two aldehyde carbons each wear a dimethyl acetal mask (four methoxy groups total), and the mask lifts only under aqueous acid to release MDA exactly where the cyclocondensation wants it. The 1,1,3,3-Tetramethoxypropane CAS No.102-52-3 — Malonaldehyde Bis Dimethyl Acetal TMOP C7H16O4 EINECS 203-037-2 Colorless Transparent Liquid 99 Percent Purity Four Methoxy Groups Protected Malonaldehyde Precursor Acid Hydrolysis C3 Building Block For Pyrimidine Pyrazole Cyanine Dye Pharmaceutical Agrochemical Intermediate Methoxylating Agent 200kg HDPE Drum UN3272 PG III Hazard Class 3 HS 2909199090 Jinghong Code JH026 OEM Supplier Hubei Jinghong Chemical Xiangyang Hubei Hbjhchem is that synthon in its JH026 grade: colorless transparent liquid, 99% assay, d 0.997 g/mL, bp 183℃ (70–75℃/15 mmHg), n20/D 1.407, flash 57℃ closed cup, moisture-sensitive, packed 200 kg HDPE drum, UN 3272 PG III, Hazard Class 3, HS 2909199090. But why do the four methoxy groups function as a 2-step deprotection handle rather than dead weight, how does in-situ MDA beat pre-formed MDA in a pyrimidine ring closure, and what makes Hubei Jinghong (Xiangyang plant, acetylene→vinyl ether→glutaraldehyde→TMOP chain) a synthon producer rather than a trader repacking a Sigma bottle? Below is the full breakdown for medicinal chemists, dye-house formulators, agrochemical R&D, and GMP intermediate buyers evaluating a C3 synthon whose real spec is "MDA released on command, not on the shelf."
Why tetramethyl acetal protection is the only shippable form of malonaldehyde
The 1,1,3,3-Tetramethoxypropane CAS No.102-52-3 — Malonaldehyde Bis Dimethyl Acetal TMOP C7H16O4 EINECS 203-037-2 Colorless Transparent Liquid 99 Percent Purity Four Methoxy Groups Protected Malonaldehyde Precursor Acid Hydrolysis C3 Building Block For Pyrimidine Pyrazole Cyanine Dye Pharmaceutical Agrochemical Intermediate Methoxylating Agent 200kg HDPE Drum UN3272 PG III Hazard Class 3 HS 2909199090 Jinghong Code JH026 OEM Supplier Hubei Jinghong Chemical Xiangyang Hubei Hbjhchem rests on five reconciled facts—acetal stability, in-situ release, heterocycle scope, dye-chain spine, and cluster-scale supply:
Four Methoxy Groups = Two Dimethyl Acetals, Stable At pH 4–9, Labile At pH <3. Each aldehyde carbon of malonaldehyde is masked as –CH(OCH3)2. In neutral or mildly basic organic media (THF, MeOH, toluene, DCM) the acetals survive distillation, column chromatography, and 6-month storage at <30℃—which is why TMOP ships as a 99% colorless liquid and not a brown tar. Drop the pH below 3 with aqueous HCl, p-TsOH, or acetic acid/water, and both acetals hydrolyze in sequence within 20–40 min at 40–60℃, releasing free MDA and 4 equivalents of methanol. The chemist controls MDA concentration locally, avoids the 1–5% MDA commercial solution that polymerizes in a week, and never handles the neat toxin. That "mask on the shelf, unmask in the pot" logic is the entire reason CAS 102-52-3 exists as a traded commodity.
In-Situ MDA Beats Pre-Formed MDA In Pyrimidine / Pyrazole Cyclocondensation. A typical pyrimidine closure pairs TMOP with urea, thiourea, guanidine, or amidine under acid catalysis: the in-situ MDA condenses with the N-C-N fragment to close the six-membered ring at 60–80℃ in one pot, yielding 2-amino-4,6-dihydroxypyrimidine, barbituric acid analogs, or uracil precursors at 70–85% isolated yield. Using pre-formed MDA solution gives 20–30% lower yield because half the MDA oligomerizes before the amidine arrives. For pyrazoles, TMOP + hydrazine derivative + β-keto ester under AcOH gives 3,5-disubstituted pyrazoles without isolating the dialdehyde. The 99% JH026 assay matters here: every 1% impurity is a competing electrophile that forks the cyclocondensation into side-pyrimidines.
C3 Spine Of Polymethine / Cyanine Dyes. TMOP is the commercial source of the –CH=CH–CH=– three-carbon conjugated unit in cyanine and merocyanine dyes. Acid hydrolysis in the presence of aniline derivatives or active methylene compounds extends the polymethine chain; photographic sensitizers, NIR fluorescent probes, and optical-data-storage media all trace their C3 core back to CAS 102-52-3. A dye house buying TMOP is not buying an "intermediate," it is buying the conjugated backbone that determines λmax; batch-to-batch n20/D 1.407 consistency (Jinghong COA) translates directly to ±2 nm dye reproducibility.
Moisture-Sensitive But Not Air-Sensitive; UN 3272 PG III Logistics. TMOP is a Flam. Liq. 3 (GHS02, H226), flash 57℃ closed cup, WGK 1, not classified as toxic (LD50 rabbit oral 2440 mg/kg). It hydrolyzes slowly in standing water but is stable in dry solvent; hence the 200 kg HDPE drum with PE liner, stored <30℃, away from acids and oxidizers. UN 3272 PG III, Hazard Class 3, HS 2909199090 keeps it in the flammable-liquid lane—ADR/IMDG compliant, no poison schedule, roughly 4–6% lower freight than a Class 6.1 aldehyde. For a European dye intermediate importer, that HS code decides whether the drum enters Rotterdam as general flammable or triggers a poison-handling surcharge.
Hubei Jinghong / Xiangyang Acetylene Cluster Co-Location. Hubei Jinghong Chemical Co., Ltd. (Jinghong Code JH026 for TMOP), Xiangcheng Economic Development Zone, Xiangyang, Hubei—same site that runs 25,000 t/a acrolein, 20,000 t/a glutaraldehyde, 15,000 t/a vinyl ether series, emamectin benzoate. TMOP is synthesized from acrolein→malonaldehyde chemistry→acetalization with methanol under acid resin; co-locating with the acrolein generator and the methanol recovery column cuts the acetone/methanol solvent cost ~18% versus a stand-alone fine-chem workshop. Not a trader relabeling a Wuhan drum; a C3-aldol/acetal specialist whose TMOP shares the QA lab, the GC-MS, and the REACH dossier with glutaraldehyde and vinyl ethers on the same PO. The 200 kg HDPE drum, COA (assay ≥99.0%, water ≤0.10%, acid ≤0.05%), and EN/ZH MSDS ship from Xiangyang to Shanghai/Ningbo in 7 days.
