Rotation of PPL by opticaly active compounds (mathematical feeling)

In summary: If M is changed then theta will change. If c is changed then θ will change. If both M and c are changed then both theta and θ will change.
  • #1
namanjain
70
0
i read formulae in textbook :

[α]λt°C = Θ/L*C ...(i)

where Θ is rotation in light
and L is length of tube
and C is concentration in gm/litre

if we consider tube of lenth L and cross section area 'A'
then C= M/A*L
M is mass of sample

so (i) becomes

[α]λt°C = Θ/[M/A]

so are scientist so blind to observe or i am doing something wrong.
 
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  • #2
This appears to be a variation on Verdet's equation for measuring the concentration of an optically active substance, allowing for temperature variations.

You have neatly removed the variable for concentration.
 
  • #3
To blind to observe what?
Your formula is correct, however, I doubt that it is more practical. The point is that you would have to fill the sample of the given mass in a tube which has precisely the cross section you sprecified. Have you tried to fill a tube with precisely the amount of substance you want and to put glass windows on it without neither liquid spilling out or gas bubbles remaining inside?
 
  • #4
DrDu said:
To blind to observe what?
Your formula is correct, however, I doubt that it is more practical. The point is that you would have to fill the sample of the given mass in a tube which has precisely the cross section you sprecified. Have you tried to fill a tube with precisely the amount of substance you want and to put glass windows on it without neither liquid spilling out or gas bubbles remaining inside?

DO IMPROVIZE MY LAST STATEMENT I WANT TO ASK:
the older equation has a feeling that if length of tube is increased one of factor will have to change and my equation marks that rotation(θ) and [α] are both independent of length of tube. I am just a bit confused for example help out with this

Q) if length of tube is doubled what will be the effect on Θ?
 
  • #5
Depends on what you hold constant. If M is constant, nothing, if c is constant, theta will double.
 

1. What is the definition of optical rotation in chemistry?

Optical rotation is the ability of a substance to rotate the plane of polarized light passing through it. This phenomenon is observed in chiral compounds, which have a specific arrangement of atoms that causes them to interact with light in a unique way.

2. How is optical rotation measured?

Optical rotation is measured using a polarimeter, which is a device that measures the angle of rotation of polarized light passing through a sample of a compound. The amount of rotation is directly proportional to the concentration of the compound and the length of the sample tube.

3. What is the relationship between specific rotation and concentration?

Specific rotation is a measure of a compound's ability to rotate light and is defined as the angle of rotation divided by the concentration of the compound and the length of the sample tube. This value is a constant for a particular compound at a specific concentration and temperature.

4. How does temperature affect optical rotation?

Temperature has a significant effect on optical rotation. As the temperature increases, the molecules in a sample of a compound will move more rapidly, leading to a decrease in the observed rotation. Therefore, the temperature must be controlled and specified when reporting optical rotation values.

5. What is the mathematical relationship between optical rotation and molecular structure?

The mathematical relationship between optical rotation and molecular structure is complex and cannot be described by a simple equation. The specific rotation of a compound is influenced by its molecular structure and the arrangement of its chiral centers, but other factors such as solvent, temperature, and concentration also play a role.

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