Capping B (Acetonitril / 2,6-Lutidine / N-methylimidazole; V / V / V = 50 / 30 / 20)

For each synthesis cycle, up to 1 to 2% of free 5’-hydroxy groups remain after the phosphoramidite coupling step has been completed. By running a subsequent „Capping“ step using an anhydride, these free hydroxyl groups are converted to acetates and are hindered from further chain elongation and formation of long oligonucleotides with incorrect sequences.

For optimal acetylation, a solution of acetic anhydride in Tetrahydrofuran or acetonitrile (Capping A) will be mixed in situ during reaction with a catalytic acting solution of N-methylimidazole (Capping B). Additives such as pyridine and lutidine function as mild bases to enhance the efficiency of the capping reaction.

Product Name: Capping B
Description: 50% Acetonitrile, 30% 2,6-Lutidine, 20% 1-Methylimidazole (v/v/v)
CAS Number: Acetonitrile/75-05-8, 2,6-Lutidine/108-48-5, 1-Methylimidazole/616-47-7
Appearance: Clear Solution
Refractive Index: 1,419 – 1,425
Water Content: ≤ 50.0 ppm
Density (g/L): 875.98

Shipping: Ambient
Storage: Ambient

Application Note
Capping reagent for nucleic acid synthesis

Cas Number: 75-05-8

Einecs Number: 200-835-2

HS Code / Commodity Code: 38249992

UN Number: 2924

Hazard Class: 3

Packing Group: 2

Hazard Phrases: H225,H302+H312+H332,H314

Prec Phrases: P210,P260,P280,P302+P352,P305+P351+P338,P403+P233