C-14 Carbon-14 Labeling & Synthesis Techniques

Question 1

What is the established half-life of Carbon-14?

Accepted Answer

5,730 years

Answer

5,268 years

Answer

1,600 years

Answer

12.3 years

Question 2

What type of radiation does Carbon-14 emit during its decay?

Accepted Answer

Low-energy beta particles

Answer

Alpha particles

Answer

Gamma rays

Answer

Positrons

Question 3

What does 'specific activity' mean for a C-14 labeled compound?

Accepted Answer

The amount of radioactivity per unit mass or mole (e.g., Ci/mmol or GBq/mmol)

Answer

The chemical purity percentage of the compound

Answer

The rate of radiolytic decomposition over time

Answer

The percentage of label located at a single molecular position

Question 4

In C-14 synthesis, what does 'position-specific labeling' mean?

Accepted Answer

Placing C-14 at one defined, predetermined carbon position within the molecular structure

Answer

Incorporating C-14 at every carbon position in a molecule

Answer

Using multiple radioisotopes simultaneously in the same molecule

Answer

Labeling only the terminal carbons of an aliphatic chain

Question 5

Which primary approach is used to introduce C-14 into organic molecules at specific positions during synthesis?

Accepted Answer

Building the molecule from C-14 labeled small-molecule precursors such as 14CO2, K14CN, or 14CH2O

Answer

Neutron bombardment of the finished compound

Answer

Isotope exchange reactions triggered by ultraviolet light

Answer

Electrochemical reduction using C-14 coated electrodes

Question 6

What is the maximum beta particle energy (Emax) emitted by Carbon-14?

Accepted Answer

156.5 keV

Answer

18.6 keV

Answer

546 keV

Answer

1.71 MeV

Question 7

Why is C-14 often preferred over stable C-13 for metabolic tracing in pharmaceutical research?

Accepted Answer

C-14 can be detected at trace concentrations using radioactivity counting, without requiring mass spectrometry

Answer

C-14 is always less expensive to produce than C-13 enriched compounds

Answer

C-14 participates in a greater variety of chemical reactions than C-13

Answer

C-14 is metabolized more slowly, allowing longer study windows