The document discusses the physical properties of organic compounds, focusing on melting point, boiling point, density, and solubility, along with their measurement methods and influencing factors. It also outlines various separation and purification techniques such as extraction, filtration, distillation, and crystallization. Understanding these properties and techniques is essential for applications in chemistry and pharmaceutical science.

1. Physical properties of chemicals
& separation and purification
methods
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2. Presentation by:
Dr. Tanuja Nautiyal
Department of Chemistry
Sharda Public School
Almora
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3. Physical Properties
 Each organic compound has certain physical and chemical
properties.
 some of the important physical properties of organic
compounds are:
 Melting point,
 Boiling point,
 Density,
 Solubility
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4. Melting Point
Melting point for an organic substance is the
temperature, at which it changes from solid state to
liquid state.
This temperature is also referred to as freezing point at
which a compound changes its state from liquid to
solid.
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5. Melting Point
Melting point determinations have importance in various
applications. Such as:
 Making a comparison with the literature data to observe the
same temperature.
 Having a very rough idea on the purity of a substance (there
are much more available and accurate methods applied to
decide it).
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6. There are lots of factors that affect the melting point. The
chemical structure is the main factor.
 Melting points are higher for higher molecular weight
compounds.
 Impurities decrease the melting point. ice-salt mixtures , Salt
and soil , Ethylene glycol.
 Intramolecular and, in particular intermolecular forces, such as
H-bonds, dipole-dipole interactions increase the melting point.
Factors affect the Melting Point
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7.  Loosing symmetry decreases the chance of intermolecular
interactions. Solid state formation is deeply affected through
the possibility of interaction among molecules.
 Therefore, loosing symmetry, in particular through branching
lowers the melting point.
 Trans isomers are more stable than cis isomers, therefore they
have higher melting points.
Factors affect the Melting Point
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8. Measuring the Melting Point
Old Fashion Model SHARDA PUBLIC SCHOOL,
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9. New fashion model
Measuring the Melting Point
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10. Boiling Point
 Boiling point for an organic substance is the
temperature at which it changes from liquid state to
gas (vapor) state. The vapor pressure of a liquid is
also equal to the pressure of the current environment
at its boiling point temperature.
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11. Factors affecting the Boiling Point
 The lower atmospheric pressure: the lower the
boiling point
 There are structural aspects having effect on boiling
point:
 Higher molecular weight ---higher boiling point
 Intermolecular and intra-molecular interaction
 Hydrogen bonding, Dipole-dipole interaction, Vander
wals forces, Impurities, Branching; increase boiling
point
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12. Density
 A density of a substance is calculated by dividing its
weight to its volume.
 The unit generally employed for density is gm/mL or
gm/cm3.
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13.  Pressure
 Temperature
 Polar groups
 Molecular weight
 Branching
 Double and triple bonds
Factors affecting the Density
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14. Measurement of Density
 By using Pycnometers
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15. In this equation:
W1= the weight of empty pycnometer
W2= the weight of pycnometer filled with the sample
liquid
W3= the weight of pycnometer filled with the inert
liquid.
Measurement the density for liquid
sample
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16. Measuring the density for solid sample
In this equation;
w1 = the weight of pycnometer filled with the inert
liquid.
w2 = the weight of empty pycnometer.
w3 = the weight of pycnometer added a little
amount of solid sample.
w4 = the weight of inert liquid filled w3.SHARDA PUBLIC SCHOOL,
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17. Solubility
 Solubility is the degree of dissolution of a substance
in a solvent.
 The solubility of a liquid substance in another liquid
matter ---miscibility and immiscibility,
 See table for solubility page 68
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18. There are lots of interaction types that might take place in
dissolution of a substance in a liquid.
The organic molecules can not dissolve in water because;
long carbon skeletons, absence of polar functional
groups, absence of heteroatoms, absence of ionic
structures, hydrophobic character
Solubility
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19. like dissolves like
 Like dissolves like, organic substances are soluble in
organic solvent, but not all, varying depending on the
structure of both the organic substance and the organic
solvent.
 Acetone has the ability of dissolve most of the organic
molecules. For instance, the solubility of naproxen in
acetone is 0.726 mol/L, which is quite higher than its
solubility in other solvents.
Solubility
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20.  The acidic or basic property of substances is
measured in terms of pH.
 It is a measurement of the hydrogen ion
concentration.
 pH is defined as the negative logarithm
(base 10) of hydrogen ion concentration.
pH of a Solution
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21.  PH < 7 ACIDIC
 PH = 7 NEUTRAL
 PH > 7 BASIC
 PH << 7 MORE ACIDIC
 PH >> 7 MORE BASIC
pH of a Solution
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22. pH
Henderson-Hasselbach equation:
pH = pKa + log ([A-] / [HA])
•pH = pka; the concentration of ionized and non-ionized forms are
equal
•pH > pKa---the concentration of ionized >non-ionized forms
•pH < pKa---the concentration of ionized <non-ionized forms
Carboxylic acid ---pKa=4-5
HA, PH=7 more than 99 % A-
If an organic molecule is insoluble in a liquid, it precipitates.
precipitation and dissolution might be evaluated as opposite actionsSHARDA PUBLIC SCHOOL,
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23. Miscibility
 Miscibility of organic solvents is quite important.
 For instance; Some reactions utilize more than one organic
solvent to conduct a reaction as reagents or to increase the
solubility.
 Some work-up and purification studies also require the
employment of more than one solvent.
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24. Partition Coefficient
Organic compound has different solubility in different organic
solvents have applications in various experiments.
Partition coefficient is the ratio of concentration of an organic
molecule in two immiscible organic solvents. The organic
compound must be at unionized (neutral). It is important to adjust
the pH that guarantees the non-ionized state of a molecule.
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25. Partition Coefficient
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26. Distribution Coefficient
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27. Application of Distribution Coefficient
Solubility in water and lipid systems are both required for a
drug molecule to pass through different biological fluid systems
to reach to its active site.
In general, a Log(Partition coefficient) value in 3-5 range is one of
those drug-likely parameters that shows a good criteria for a
drug candidate molecule. Chloroform is sometimes used as an
alternative to n-octanol.
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28. Polar groups, groups tend to make Hydrogen bonds,
ionic bonds definitely trigger solubility in aqueous
systems, therefore resulting in low Log(Partition coefficient)
values relatively.
In contrast, lacking of those structural features and
abundance of hydrophobic groups creating london -
london forces positively affect lipophilicity and high
Log(Partition coefficient) values.
Application of Distribution Coefficient
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29. Methods of Purification
Extraction
Filtration
Distillation
Crystallization
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30. Extraction
Extraction is a separation technique.
Types of Extraction:
• Solid-liquid Extractions:
Solid liquid extractions simple aims to extract the
material from a solid mixture into a liquid.
• Liquid-liquid Extractions:
Liquid-liquid extractions employ the solubility
difference of an organic compound in two
immiscible liquids.
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31. Extraction depends on several factors:
• Solubility in two immiscible solvents
• Temperature
• The amount of each solvent used
Factors affect the Extraction
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32. Separation funnels are utilized
for liquid-liquid extraction.
Immiscible solvents separate
in funnel such that heavier
(higher density) stays at
bottom.
Liquid-liquid Extraction
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33. Liquid-liquid Extraction
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34. After the extraction process, in general, the organic
phase is evaporated to gain the organic compound.
In practice, most of the organic solvents have the ability
to dissolve some amount of water as well. The amount
of water transferred into organic phase changes
depending on the organic solvent used. Anhydrous
sodium sulfate, and anhydrous magnesium sulfate,
anhydrous calcium chloride, anhydrous cupper sulfate,
and anhydrous calcium sulfate
Drying of liquid
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35. Therefore, some drying phase changes depending on
the agents are used to have the organic solvent water
free.
Some features required form drying agents:
• No solubility in the organic solvent
• High efficiency to dry
• Inert material
Drying of liquid
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36. Filtration
Filtration is one of the most applied processes in
organic and pharmaceutical chemistry practices.
In general, filtration is categorized into two groups;
1. Gravity filtration
2. Vacuum filtration
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37. Gravity Filtration Method
Gravity filtration is the
simple form of
filtration.
Requirement: Funnel,
Filtration paper and a
Erlenmeyer..
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38. Vacuum Filtration
Vacuum filtration is much faster than gravity
filtration. The only difference is the employing of
vacuum as a deriving force for filtration.
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39. Distillation
Distillation is an old-known separation and purification
technique, particularly applied for liquids.
It is based on a system consisting of both heating and
cooling units.
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40. Distillation
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41. Fractional Distillation
Liquids that have different boiling points and do not
make azeotrope mixtures can be separated
employing the fractional distillation technique. The
difference of fractional distillation from the simple
distillation is the employment of fractional
condenser.
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42. Fractional Distillation
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43. During the separation, some liquids can form
azeotropes. The boiling point of the azeotropes might
be lower or higher than the boiling point of each
components of the azeotrope mixture.
For example: For instance, 96% ethanol boils at around
78.3 ºC which is lower than the boiling points of water
and ethanol, 100 ºC, and 78.8 ºC, respectively. Due to
the formation of azeotrope, technically it is not possible
to separate ethanol-water mixture employing fractional
distillation. In such a case, another solvent is added to
break down the azeotrope, such as benzene addition to
ethanol-water mixture.
Azeotropes
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44. Steam Distillation
This type of distillation is especially for those liquids,
that have high boiling points and decompose at high
temperatures less than their boiling point.
The steam distillation system applies the in-situ
generation of steam and applying it directly onto the
material to activate it for distillation.
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45. Steam Distillation
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46. Vacuum Distillation
It is also referred to as low-pressure distillation. boiling point of an
organic substance depends on several factors including the pressure.
The vacuum application to a distillation unit would be enough to
decrease the pressure inside the system, resulting in the boiling of a
liquid compound at temperatures lower than its regular boiling
temperature.
For instance, dimethylsulfoxide has a relatively high boiling point,
around 190 ºC. Vacuum application to the system physically takes
down the boiling point of dimethylsulfoxide. An effective vacuum can
even take it to less than 100 ºC.
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47. Low-pressure Distillation
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48. Crystallization
Crystallization is one of the oldest purification
techniques applied for solid organic compounds. It has
these stages of a continuous process summarized below:
• Dissolution
• Hot filtration
• Crystallization
• Filtration of crystal
• Drying of crystal SHARDA PUBLIC SCHOOL,
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49. Steps of Crystallization
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50. Crystallization
•The overall technique simply relies on the dissolution of
an organic compound in the presence of impurities in a
hot organic solvent concomitant with its crystallization in
the same solvent during the cooling down of the organic
solvent.
•A crystal lattice is perfectly ordered for the same type of
molecules. Therefore, crystals physically chemically
tends to form between the same type of molecules. This
also means that impurities are excluded from the crystal
lattice. SHARDA PUBLIC SCHOOL,
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51. Crystallization
Salt Chemical formula Shapes of crystals
Potash alum K2SO4.Al2(SO4)3.24H2O Octahedral
Blue vitriol CuSO4.5H2O Triclinic
Green vitriol FeSO4. 7H2O Monoclinic
Sodium chloride NaCl Cubic
Potassium nitrate KNO3 Rhombic
Washing soda Na2CO3.10H2O Monoclinic
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52. Dr. Tanuja Nautiyal
Department of Chemistry
Sharda Public School
SHARDA PUBLIC SCHOOL,
ALMORA