Surface tension

Q: What do you mean by surface tension?

Ans: It represents the intermolecular attraction due to cohesive quality at the surface of the liquid, in contact with another fluid or solid, which tends to move the molecules of the liquid inside from the surface.
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Further Reading:

Some types of reactions in Pharmacy

Q: What do you mean by acetylation?

Ans: Acetylation is a reaction for the production of acetyl derivative.

Q: What do you mean by acetyl?
Ans: It is a radical showing CH3CO- in the formula. It is obtained from acetic acid (CH3COOH) by the removal of hydroxyl group (-OH).

Q: What is the use of acetylation and give its example?
Ans: Acetylation is used to lessen the toxicity of amines in drug production. Paracetamol is produced from p-nitrophenol by the use of acetylation.

Q: What do you mean by radical?

Ans: It represents a chemical group that works as a single unit in a chemical reaction.

Q: What do you know about alkylation?
Ans: It represents a chemical reaction in which the alkyl group is introduced into the compound in place of hydrogen.

Q: What do you mean by alkyl?
Ans: It is used to represent a hydrocarbon group obtained from alkane such as an ethyl (group).

Q: Give an example of alkylation.
Ans: Caffeine, an important constituent of coffee or tea, is obtained by the methylation (alkylation) of theophylline or theobromine.
Q: What do you mean by amination?
Ans: Amination represents the insertion of amine group into a compound.

Q: Give an example of amination.

Ans: Amphetamine is obtained from phenylacetone by the process of amination.
Q: What do you mean by condensation?
Ans: It represents the conversion of gas to a liquid or liquid to a solid. It also represents the bonding of molecules for the formation of denser substance and involves the connecting together of two or more organic molecules.

Q: Give an example of product obtained by condensation.
Ans: Hexylresorcinol is obtained by the condensation of resorcinol with hexanoic acid.

Q: What do you mean by esterification?
Ans: It represents the formation of ester.

Q: Give an example of esterification.
Ans: Formation of ethyl acetate by the reaction of ethanol and acetic acid.

Dissociation

It is a process in which there is separation of ionic compounds into smaller parts (molecules or ions).

It is usually a reversible process.

It is the opposite of association and recombination.

pKa

pKa is an acid dissociation constant.

Definition:
It is the negative logarithm of the acid dissociation constant i.e., Ka

Equation:
Its equation is:
pKa = -log10 Ka

Importance:
1. It shows the extent of dissociation. As the value of pKa increases, the extent of dissociation will decrease.
2. It has the ability of telling the acidic or basic properties of a substance.

Mass analyzer

Mass analyzer is a technique used for the separation of the ions according to mass/charge ratio.

Equation for the Mass analyzer:

1. Lorentz force law:
F=Q(E+v*B)

Where
F = force applied to the ion
Q = ion charge
E = electric field
v*B = the vector cross product of the ion velocity and the magnetic field

2. Newton's second law of motion:
F=ma

Where
F = force applied to the ion
m = mass of the ion
a = acceleration

By combining the above two equations, we get:

Q(E+v*B) = ma

=> E+v*B = a(m/Q)

where m/Q denotes mass to charge ratio.

Types of mass analyzers:

There are various types of mass analyzers:

1. Scanning Mass Analyzers

2. TOF - Mass Analyzers

3. Trapped Ion Mass Analyzers

Ion Source

It is a type of an electro-magnetic instrument, primarily used to create charged particles.

It is used in ion implanters, ione engines, mass spectrometersand particle accelerators.

Mass spectrometry

Introduction:
Mass spectrometry is a technique used in analysis.

It is a form of spectrometry in which, usually, high energy electrons are bombarded onto a sample and this produces charged particles of the parent sample; these ions are then focused by electrostatic and magnetic fields to produce a spectrum of the charged fragments which is helpful in establishing the ratio of charged to mass of the particles.

Essential parts:
The design of a mass spectrometer has three essential modules:

1. An ion source:
This transforms the molecules in a sample into ionized fragments.

2. A mass analyzer:
This causes the sorting of the ions by their masses by applying electric and magnetic fields

3. A detector:
This measures the value of some indicator quantity and thus provides data for calculating the abundances of each ion fragment present.

Uses and applications:
The technique has both qualitative and quantitative uses, such as

1. Identifying unknown compounds,
2. Determining the isotopic composition of elements in a compound,
3. Determining the structure of a compound by observing its fragmentation. Its use is there in the identification and structural determination of the flavonoid glycosides. ( Maciej Stobiecki)
4. Quantifying the amount of a compound in a sample,
5. Studying the fundamentals of gas phase ion chemistry
6. Determining other physical, chemical, or biological properties of compounds.

It is now applicable in the field of proteomics. (Christine C. Wu et al.)

References:
Christine C. Wu and John R. Yates III, The application of mass spectrometry to membrane proteomics, Nature Biotechnology 21, 262 - 267

Maciej Stobiecki, 2000, Application of mass spectrometry for identification and structural studies of flavonoid glycosides , Phytochemistry, 54, 237-256

Further reading:
Mass Spectrometry: Principles and Applications by Edmond de Hoffman and Vincent Stroobant

Mass Spectrometry: A Textbook by Jürgen H. Gross