Question

Y it is more difficult to record c13 nmrthan h1 nmr

Answer 1

With 1H NMR a useful spectrum can be obtained very quickly (5 minutes) with a few milligrams of material, however with 13C NMR normally the minimum scan time would be longer (~20-30 minutes) and a more concentrated sample would be needed (~30 mg/0.6 mL) to obtain a useful spectrum. The amount of material needed should be increased as the molecular weight of the compound increases, I think I was previously told ~5 mg of sample per carbon atom per 0.6 mL of solution. So if you have an compound with a single aromatic ring 30 mg of sample may be fine but for a larger molecule 100 mg may be needed. If you only have 30 mg of a larger molecule then 4-12 hours of scanning time may be required.

Answer 2

beacuse more scanning time is used