Chemistry, Volume II Organic and Physical Chemistry

347 Pages·013.191 MB·347\347

CHEMISTRY-II
Organic and Physical Chemistry
Dr. J. N. Gurtu Dr. H. C. Khera
MoSc., Ph.D .. M.Sc., Ph. D.
Retd. Principal, Reader & Head,
Meerut College, Meerut. Chemistry Department,
loP. College, Bulandshahr.
»
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1. ORGANIC CHEMISTRY AND PURIFICATION OF ORGANIC COMPOUNDS 1-1 ~
Organic chemistry 1
Requirement and methods of purification 2
Tests of purity 10
Chromatography 12
Exercises 13
2. OUALITATIVE AND OUANTITATIVE ELEMENTAL ANALYSIS 16-'J6
Qualitative detection of elements 16
Quantitative estimation of elements 19
Exercises 32
}. EMPIRICAL, MOLECULAR AND STRUCTURAL FORMULA,
MOLECULAR MASSES OF ORGANIC COMPOUNDS
Empirical formula 37
Molecular formula 39
Molecular weight of organic acids and bases 39
Numerical problems based on empirical, molecular and structural formulae 42
Exercises 52
4. TETRAVALENT CHARACTER OF CARBON, FUNCTIONAL GROUPS AND
NOMENCLATURE OF ORGANIC COMPOUNDS n-8}
Tetrahedral concept of carbon atom 53
Functional groups 54
Nomenclature of organic compounds 55
Exercises 72
~. SATURATED HYDROCARBONS, ALKANES OR PARAFFINS 84-94
Alkanes or paraffins 84
Nomenclature of alkanes 84
General methods of preparation of alkanes 85
General properties of alkanes 88
Exercises 92
6. UNSATURATED HYDROCARBONS (ALKENES AND ALKYNES) 9~-114
Alkenes or olefins 95
Nomenclature of alkenes 95
General methods of preparation of alkenes 96
General properties of alkenes 98
Alkynes or acetylenes 103
Nomenclature of alkynes 103
General methods of preparation of alkynes 104
General properties of alkynes 105
Acidic nature of hydrogen in acetylene 109
Ascent and descent of alkane series and important conversions 110
Exercises 111
7. HALOGEN SUBSTITUTED ALKANES l1~-no
Monohalogen derivatives of alkanes 115
Ethyl bromide or bromoethane 119
Dihalogen derivatives of alkanes 122
Trihalogen derivatives of alkanes 123
Chloroform (Trichloromethane) 123
Exercises 128
8. ORGANOMETALLIC COMPOUNDS AND GRIGNARD'S REAGENT 111-14'J
Organometallic compounds 131
Exercises 143
9. PREPARATION, PROPERTIES AND USES OF COMPOUNDS 144-161
(Ethanol, Glycol and Glycerol)
Alcohols 144
Ethyl alcohol or ethanol 146
Glycols 150
Glycerol 153
Exercises 160
10. ALDEHYDES AND KETONES 162-18)
Introduction 162
Classification 163
Nomenclature 163
General methods of preparation 164
General properties of aldehydes and ketones 166
Formaldehyde or methanal 176
Acetaldehyde or ethanal 177
Acetone or propanone or dimethyl ketone 180
Exercises 181
11. MONOCARBOXYLIC ACIDS AND THEIR DERIVATIVES 184-207
Carboxylic acids 185
Carboxylic acid derivatives 194
Acid anhydrides 195
Acid halides 197
Acid amides 200
Acid esters 202
Exercise& 206
12. DICARBOXYLIC AND TRICARBOXYLIC ACIDS 208-222
Malic acid 208
Tartaric acid 209
Oxalic acid or ethanedioic acid 213
Maleic acid 215
Fumaric acid 217
CItric acid 217
Exercises 221
ll. UREA 221-227
Exercises 226
14. ISOMERISM 228-240
Explanation and definition of isomerism 228
Types of isomerism 228
Exercises 238
1~. STRUCTURE AND BONDING 241-2~8
Hybridisation 241
Bond length 243
Bond angle 244
Bond energy 245
vander Waals interactions 247
Resonance 248
Hyperconjugation or no bond resonance 250
Inductive effect 253
Hydrogen bonding 256
Exercises 257
16. ARENES AND AROMATICITY 2~9-271
Aromatic hydrocarbons or arenes 259
Benzene 259
Constitution of benzene 265
Aromaticity 269
Huckel's (4n + 2) rule 270
Exercises 271
17.THERMODYNAMICS 272-286
Basic definitions 272
Energy 276
Internal energy 276
First law of thermodynamics 277
Heat changes 278
Heat content or enthalpy 278
Heat capacity of system 279
Spontaneous and non-spontaneous processes 280
Second law ofthermodynamics 281
Concept of entropy 282
Exercises 285
18. NUCLEAR CHEMISTRY 287-l08
Nucleus 287
Isotopes 287
Isobars 289
Isotones 290
Natural radioactivity 290
Artificial disintegration or transmutation of atoms 293
Artificial radioactivity 294
Detection and measurement of radioactivity 295
Radioactive decay as first order reaction 298
Binding energy 300
Nuclear reaction equations 301
Nuclear fission (atomic fission) 302
Nuclear fusion (atomic fusion) 303
Transuranic elements 304
Applications of radioactivity and radioisotopes 304
Exercises 307
CHEMISTRY PRACTICALS }09-}40
Volumetric analysis 311
Types oftitrations 316
Exp. 1. To prepare N/10 standard solution of ferrous ammonium sulphate and
find out the strength of the supplied ferrous ammonium sulphate using
potassium permaganate solution as an intermediate solution. 317
Exp.2. To prepare N/10 standard solution of oxalic acid and find out the
strength of the given oxalic acid solution by using potassium
permanganate solution as an intermediate solution. 318
Exp.3. To prepare N/30 standard solution of ferrous ammonium sulphate and
find out the strength of supplied ferrous ammonium sulphate solution by
319
using K2Cr207 solution as an intermediate solution.
Exp.4. To prepare N/30 standard solution of ferrous ammonium sulphate and
find out the strength of the given ferrous ammonium sulphate solution
by using K2Cr207 solution as an intermediate solution (internal
320
indicator)
Exp.5: To prepare N/30 standard solution of potassium dichromate and find out
the strength of given potassium dichromate solution using ferrous
ammonium sulphate as an intermediate solution (internalindicator). 321
Exp.6. To prepare N/30 copper sulphate solution and find out the strength of the
given copper sulphate solution by titrating it with sodium thiosulphate
solution iodometrically. 322
Exp. 7. To prepare N/30 K2Cr207 solution and find out the strength of the given
K2Cr207 solution by titrating it against sodium thiosulphate solution
iodometrically. 324
PHYSICAL CHEMISTRY EXPERIMENTS l26
Surface tension 326
Exp. 1. To find the surface tension ofthe given liquid by drop number method at
room temperature. 328
Viscosity 329
Exp.2. To find the relative and absolute viscosity of the given liquid at room
temperature. 331
Thermochemistry 332
Exp.3. To find the water equivalent of a calorimeter. 333
Exp.4. To find out the heat of neutralisation of sodium hydroxide and
hydrochlOrIC acid. 334
Solubility 337
Exp. 5. To determine the solubility of potassium nitrate at room temperature
and also to draw its solubility curve. 339
CHAPTER 1
ORGANIC CHEMISTRY AND
PURIFICATION OF ORGANIC COMPOUNDS
ORGANIC CHEMISTRY
The term organic signifies life. Berzelius in early nineteenth century proposed
'vital force theory', according to which organic compounds could be obtained from
sources containing life, i.e., from living organisms, e.g., animals and vegetable
sources.
However, in 1828, Wohler, a German chemist gave the first blow to the vital
force theory. He prepared the first organic compound, urea (a compound present
in the urine of animals) in laboratory by heating a mixture of ammonium sulphate
and potassium cyanate.
(NH4)2S04 + 2KCNO ---7 2NH4CNO + K2S04
Ammonium sulphate Potassium cyanate Ammonium cyanate
NH4CNO ---7 NH2CONH2
Urea
The work did not at once disturb the belief in vital force theory. But the
synthesis (preparation of compound from its elements) of acetic acid by Kolbe in
1845, gave the final blow to vital force theory. Soon after, methane was also
synthesised by Berthelot in 1856, therefore, the term organic lost its original
significance.
It was Lavoisier who showed that carbon was the essential element of organic
compounds. Accordingly, organic compounds are now defined as 'the compounds of
carbon' and organic chemistry as the study of these compounds.
[I] Justification for Separate Study
The reason to study compounds of carbon separately, coming under the heading
of organic compounds, is the large number of their typical characteristics.
At present, over two million organic compounds are known and each year the
number of new organic compounds discovered or synthesised, sometimes exceed
the total number of compounds of all the remaining elements (nearly 75,000 are
known), This provides sufficient justification for their study as a separate branch
of chemistry.
[II] Characteristics of Organic Compounds
(i) All the organic compounds are covalent compounds.
(ii) The carbon present in organic compounds is always tetravalent, i.e .•
tetracovalent.
(iii) Unlike inorganic compounds, most of them are insoluble in water.
2 CHEMISTRY-II (BIOTECH.)
(iv) Most of the organic compounds possess low m.p. or b.p. as compared to
inorganic compounds.
(v) Perhaps the most important characteristic property is the phenomenon
of 'isomerism', which may be defined as "when two or more compounds
possess the same molecular formula but differ in their properties". Such
compounds are called 'isomers' and the phenomenon as 'isomerism'. The
phenomenon of isomerism is exhibited by organic compounds due to their
highly directional covalent bonds.
(vi) Another characteristic of organic compounds is the presence of
'catenation property', actually a property of carbon, which means the
tendency to link together. The carbon atoms unite with each other by all
possible means including linking through single, double or triple bonds,
forming straight or branched chains or cyclic compounds. It is this
property of carbon which is mainly responsible for such a large number
of organic compounds known.
REQUIREMENT AND METHODS OF PURIFICATION
[I] Requirement of Purification
Since most of the organic compounds are isolated from natural sources where
they are present along with other organic compounds with identical properties, it
is essential to purifY them before subjecting them to qualitative and quantitative
analysis. Unlike inorganic compounds, the purification of organic compounds is
tedious as large number of them decompose on heating, are sensitive to other
reagents and resist the solvent action of water.
[II] Methods of Purification
Separation and purification of organic compounds depend mainly on the
difference of physical properties of organic compounds. The main methods of
purification of organic solids and liquids are as follows :
(1) Purification of Organic Solids
(i) S'imple crystallisation
This method is used to purify those organic compounds which are mixed either
with insoluble impurities or less soluble impurities.
Principle: Each organic compound is more soluble in a particular solvent at
higher temperature but less soluble at lower
temperature.
The process includes the preparation of a
saturated solution of the solid at a higher
temperature and then separating the solid in pure
form by cooling the solution.
The method is also employed in inorganic
chemistry. The only difference in the case of organic
compounds is the use of various organic solvents,
e.g., alcohol, benzene, ether, acetone, chloroform
etc., apart from the use of water. The success of the
method depends upon the selection of suitable
solvent. A good solvent must have low boiling point Fig. 1. Hot water funnel
ORGANIC CHEMISTRY AND PURIFICATION OF ORGANIC COMPOUNDS 3
Whatman
tilter paper ~~:=~
Trap.
Fig. 2. Filtration by using filter pump
and easy vaporisation. Moreover, the solid to be purified should be more soluble
at high temperature but less at a low temperature so that cooling should lead to
crystallisation.
Method : The crystallisation of an organic solid involves the following
procedure:
A saturated solution ofthe solid to be purified is prepared at high temperature.
It is decolorised, if necessary, by heating or refluxing with animal charcoal, and
filtered while hot through a hot water funnel (Fig. 1) using filter pump (Fig. 2). A
hot water funnel is·an ordinary funnel surrounded by a double walled copper jacket
between which hot water is filled. This keeps the funnel hot and thus prevents
cooling and consequent crystallization of the solid over the filter paper during
filtration.
The filtrate is then allowed to cool in a shallow container when pure solid starts
depositing in the form of crystals leaving behind impurities in the mother liquor.
Crystals thus obtained are separated by filtration or by centrifuging. Filtration is
generally done on a Buchner funnel applying a little
vacuum by using a filter pump (Fig. 2) to expedite the
procedure.
Normally, after the first filtration, the crystals,
separated on filter paper, are washed once or twice by
the same solvent in order to remove any adhering
impurity. Crystals thus obtained may further be
purified by recrystallisation.
Crystals of pure compound are kept in a vacuum
desiccator (Fig. 3). A vacuum desiccator differs from
an ordinary one in that it has on the top a tube which
is connected to a suction pump to suck out the air from
desiccator. Fig. 3. Vacuum desiccator