Question

It has been assumed that the only compound in your carrot extract that absorbs at 449 nm is β- carotene. How could this be proved? How many grams of carrots must you eat each day to meet your recommended daily dietary allowance of retinol? Show all calculations neatly and clearly, including units. 7.

Answer 1

6. Beta-carotene is a highly conjugated compound. It contains 11 C-C double bonds which are in conjugation. So, as we move from less conjugation to more conjugation, the compound becomes more and more stable. The stability decreases the energy difference between electronic levels. So, the electronic transition becomes easy and it absorbs less energy to excite lower energy level to higher. Less is the energy, more is the wavelength. So, beta carotene absorbs in the visible region, which starts from 380 nm approximately. beta-carotene also absorbs at 449 nm, so we can confirm that the compound is beta carotene.

7. The daily dietary allowance for retinol for a human being is around 1000 $\mu$g RAE per day. And 100 g of carrots contain 835 $\mu$g RAE.

So, if 835 $\mu$g RAE is present in 100 g carrots, then 1000 $\mu$g RAE can be obtained from = 100*1000/835 = 119.8 g of carrots are required daily.