API-Grade 2-Amino-4-Chloropyrimidine COA: Halogenated Impurity Limits & Color Index Drift
API-Grade 2-Amino-4-Chloropyrimidine COA: Halogenated Impurity Limits & Color Index Drift
For procurement managers sourcing 2-amino-4-chloropyrimidine (CAS 3993-78-0) as a pharmaceutical intermediate, the Certificate of Analysis (COA) is the definitive document that separates industrial-grade material from true API-grade. This heterocyclic building block, also referred to as 4-chloro-2-aminopyrimidine or 2-amine-4-chloropyrimidine, is a critical precursor in the synthesis of antiretroviral agents like Rilpivirine. When evaluating bulk lots, two parameters demand rigorous scrutiny: the halogenated impurity profile, particularly the 4,6-dichloro isomer, and the APHA color index, which can drift under suboptimal storage or synthesis conditions. At NINGBO INNO PHARMCHEM, we treat these as non-negotiable quality gates, ensuring our material functions as a seamless drop-in replacement for established supply chains without reformulation or process adjustments.
Our manufacturing process is designed to minimize the formation of the 4,6-dichloro impurity, which is a common byproduct in the chlorination step of the synthesis route. Through controlled stoichiometry and precise temperature ramping, we consistently achieve levels below 0.5% as quantified by GC-MS. This is not merely a specification on paper; it directly impacts the downstream organic synthesis of diarylpyrimidine (DAPY) derivatives. For a deeper dive into how catalyst poisoning and solvent kinetics affect this impurity profile, refer to our technical discussion on sourcing 2-amino-4-chloropyrimidine for DAPY synthesis.
From a field perspective, one non-standard parameter that often catches procurement teams off guard is the viscosity shift of molten 2-amino-4-chloropyrimidine at sub-zero temperatures during winter transport. While the material is typically a crystalline solid at ambient conditions, residual solvents or polymorphic variations can lead to a semi-solid consistency in unheated warehouses, complicating drum discharge. We address this by recommending controlled pre-heating of IBCs or 210L drums to 30–35°C before use, a practice detailed in our article on bulk 2-amino-4-chloropyrimidine polymorph control and winter filtration. This hands-on knowledge prevents costly downtime in continuous manufacturing lines.
4,6-Dichloro Impurity Threshold: Impact on HPLC Peak Tailing in Final APIs
The 4,6-dichloro impurity (CAS 1193-21-1) is structurally similar to the target molecule, making its removal challenging via simple recrystallization. In HPLC analysis, even trace amounts can cause peak tailing that obscures the purity assessment of the final API. Our specification caps this impurity at ≤0.5% (area normalization by GC-MS), a threshold validated through collaborative studies with generic drug manufacturers. Exceeding this limit not only complicates purification but can also lead to genotoxic concerns, as halogenated pyrimidines are flagged in ICH M7 assessments. We provide batch-specific COAs with chromatograms, allowing your QC team to verify the absence of co-eluting peaks.
| Parameter | API-Grade Specification | Industrial Grade Typical |
|---|---|---|
| Assay (HPLC) | ≥99.0% | ≥97.0% |
| 4,6-Dichloro Impurity | ≤0.5% | ≤2.0% |
| APHA Color (10% in Methanol) | ≤150 | ≤300 |
| Water Content (KF) | ≤0.5% | ≤1.0% |
| Residue on Ignition | ≤0.1% | ≤0.3% |
It is important to note that the CAS number 7461-50-9, often queried in relation to chloropyrimidines, corresponds to 2,4-dichloropyrimidine, a different regioisomer. The correct identifier for our product is 3993-78-0, sometimes listed as 2-amino-4-chloro-pyrimidine. Confusion with 2-chloropyrimidin-4-amine (which is the same compound) or 4-chloro-2-aminopyridine (CAS 19798-80-2) can lead to procurement errors. Always cross-reference the CAS number with the desired substitution pattern.
APHA Color Drift Above 150: Correlation with Crystallization Opacity and Recrystallization Cycles
The APHA color index is a sensitive indicator of oxidative degradation or trace metal contamination. In our experience, batches stored under nitrogen-blanketed conditions maintain an APHA value below 100 for over 12 months. However, exposure to humidity or elevated temperatures can trigger a color drift toward yellow-brown, with APHA values exceeding 150. This discoloration is not merely aesthetic; it correlates with the formation of insoluble oligomers that increase crystallization opacity. When the color index drifts, downstream recrystallization yields drop by 5–8%, and the resulting crystals exhibit a dull appearance unacceptable for parenteral-grade APIs. We recommend that procurement teams request a COA with APHA measured at the time of shipment, not just at production release, to account for any transit-induced changes.
Another edge-case behavior we've documented is the impact of trace iron on color stability. Even at sub-ppm levels, iron catalyzes the formation of colored complexes during the manufacturing process. Our quality control includes ICP-MS screening for transition metals, a parameter not typically listed on standard COAs but available upon request. This proactive approach ensures that the high purity grade material you receive will not introduce unexpected color bodies into your reaction stream.
Bulk Packaging and Supply Chain Reliability for Industrial-Scale Procurement
For tonnage-scale procurement, packaging integrity is as critical as chemical purity. We supply 2-amino-4-chloropyrimidine in 25 kg fiber drums, 210L steel drums, or 1000L IBCs, all with moisture-barrier liners. Our logistics protocols are designed to maintain product integrity during ocean freight, including desiccant packs and temperature loggers for sensitive shipments. While we do not claim EU REACH compliance, our packaging meets international transport regulations for hazardous chemicals (Class 9, UN 3077). We maintain safety stock at multiple warehouses to buffer against supply disruptions, a key advantage for buyers seeking a reliable global manufacturer.
Procurement managers evaluating bulk price competitiveness should consider total landed cost, including the avoidance of rework due to off-spec material. Our batch-to-batch consistency, documented through statistical process control charts, minimizes the need for incoming QC adjustments. This reliability is why several generic API producers have qualified our material as a direct substitute for higher-cost sources, without any change to their regulatory filings.
Frequently Asked Questions
What is the acceptable APHA range for clear downstream crystallization?
For most pharmaceutical applications, an APHA value ≤150 (10% solution in methanol) is acceptable. However, for colorless final APIs, we recommend sourcing material with APHA ≤100 to avoid additional decolorization steps. Batches with APHA >150 often require an extra recrystallization cycle, increasing solvent usage and cycle time.
How is the 4,6-dichloro impurity quantified via GC-MS?
We use a validated GC-MS method with a DB-5MS column (30 m × 0.25 mm, 0.25 µm film). The sample is dissolved in dichloromethane at 1 mg/mL, and 1 µL is injected in split mode (20:1). The oven program ramps from 80°C to 280°C at 15°C/min. The 4,6-dichloro impurity elutes at approximately 8.2 minutes and is quantified against a certified reference standard using selected ion monitoring (SIM) for m/z 148, 150, and 152. The limit of quantification is 0.05%.
What is CAS number 7461-50-9?
CAS 7461-50-9 is 2,4-dichloropyrimidine, a related compound but not the same as 2-amino-4-chloropyrimidine (CAS 3993-78-0). The former has two chlorine substituents, while our product has an amino group at the 2-position and a chlorine at the 4-position.
What is the CAS number of 2-Chloropyrimidin-4-amine?
2-Chloropyrimidin-4-amine is a synonym for 2-amino-4-chloropyrimidine, and its CAS number is 3993-78-0. This nomenclature variation arises from different naming conventions but refers to the identical chemical structure.
Is 2,4-diamino-6-chloropyrimidine soluble in water?
2,4-Diamino-6-chloropyrimidine (CAS 156-83-2) has limited water solubility (approximately 2 g/L at 25°C). In contrast, 2-amino-4-chloropyrimidine is slightly more soluble in polar organic solvents like methanol and ethanol, which are typically used for recrystallization.
What is the CAS number for 4-chloro-2-aminopyridine?
The CAS number for 4-chloro-2-aminopyridine is 19798-80-2. This is a pyridine derivative, not a pyrimidine, and should not be confused with 2-amino-4-chloropyrimidine. Always verify the heterocyclic core when ordering.
Sourcing and Technical Support
When procuring API-grade 2-amino-4-chloropyrimidine, the COA is your first line of defense against batch variability. By setting tight limits on halogenated impurities and monitoring color drift, you safeguard your downstream synthesis and final product quality. Our team provides comprehensive documentation, including residual solvent profiles and particle size distribution upon request, ensuring a smooth technology transfer. Ready to optimize your supply chain? Reach out to our logistics team today for comprehensive specifications and tonnage availability.