Chemistry Subdisciplines | The Canadian Encyclopedia


Chemistry Subdisciplines

Early chemistry was principally analytical in nature; only as the body of experimental data increased did the present-day specialities evolve. The principal chemical subdisciplines are analytical, inorganic, organic and physical chemistry.
John Polanyi, scientist
John Polanyi receiving his share of the Nobel Prize in Chemistry from King Carl Gustaf of Sweden, 10 December 1986 (photo by Rolf Hamilton, Pressens Bild).

Chemistry Subdisciplines

Early chemistry was principally analytical in nature; only as the body of experimental data increased did the present-day specialities evolve. The principal chemical subdisciplines are analytical, inorganic, organic and physical chemistry.

Analytical Chemistry
Analytical chemistry is the science of recognizing different substances and determining their constituents. Satisfactory methods are available for analysis of most of the major components of a material. The main problems arise in analysing for a sample. Classical methods such as those using weight and volume (gravimetric and volumetric methods, respectively) are still used in analysis for major components and for standardization; however, measurement techniques have become increasingly sophisticated as desired detection limits continue to be lowered.

For example, although all elements in Earth's crust are found in the ocean, only a dozen or so have concentrations above one part per million; most are at the part per billion level or less. Methods are being sought for nanogram (10 -9) to picogram (10 -12) quantities in a wide range of materials.

Analysis at these levels requires more sensitive techniques and reduction of background effects; losses and contamination during sampling and storage become highly significant. As a result, considerable attention is being devoted to new preconcentration procedures that selectively concentrate and separate species of interest.

Analytical procedures have been developed that use almost all the known chemical and physical properties of both atomic and molecular species. Procedures based on solution reactions, absorption and emission of radiation, thermal properties, optical properties, magnetic field effects and electroanalytical behaviour are in common use. Computers have become commonplace for automation and handling of data.

Analytical chemistry contributes to daily living through the identification and monitoring of toxic substances in the environment and through the range of laboratory work required in industry (eg, metals, petrochemicals, food and beverages), the biological sciences (eg, medicine) and the physical sciences (eg, geology).

Most screening programs and routine quality control analyses are performed by automated equipment operated by technicians; analytical chemists advise on the selection of equipment, produce and develop new units, and ensure that procedures are scientifically sound.

The analytical chemistry community in Canada consists of scientists in the academic, government and industrial sectors. In the period from WWII to 1960, the academic sector was small, with McGill (G. Cove), Carleton (C. Chakrabarti), McMaster (R. Graham), Alberta (W. Harris), Waterloo (W. McBryde), Queens (J. Page) and Dalhousie (D. Ryan) each having only one staff member carrying out analytical chemistry research.

By 1991 there had been considerable growth in the discipline, with Alberta and Dalhousie each having 6 or more analytical academic staff and British Columbia, Calgary, Saskatchewan, Guelph-Waterloo, McMaster, Toronto, McGill and Montreal all having 3 or more analytical academic staff. The total academic analytical sector now consists of over 50 staff members throughout Canada.

Canada has a number of strong analytical laboratories in the government sector. Among these are the Geological Survey of Canada, the Environment Commissioner of Ontario, Environment Canada, the Ontario Geological Survey and the Analytical Chemistry Section of the Division of Chemistry at the NATIONAL RESEARCH COUNCIL of Canada (NRC).

The latter laboratory, headed by S. Berman, is now the Measurement Sciences Section of the Institute for Environmental Chemistry at NRC and is recognized worldwide for its program directed toward the development of marine reference materials and standards for water, biological tissues and sediments.

The industrial sector of analytical chemistry is less robust. While many industries have excellent analytical support laboratories, the companies actually manufacturing and developing new analytical instruments are rare in Canada. In the early and mid-1980s, Photochemical Research Associates of London, Ontario, developed a strong line of spectrometric instrumentation, only to fail in the latter part of the 1980s, with most of its product lines now taken over by US interests (Laser Photonics, Photon Technology and LECO). Bomen Inc. of Québec City has an internationally marketed range of Fourier transform spectrometers, but recently became partly owned by offshore interests (Applied Automation/Hartmann and Braun).

The most successful Canadian company in the field of analytical instrumentation is SCIEX of Thornhill, Ontario. Since the early 1970s, they have developed and marketed a unique range of products based on atmospheric sampling interfaces for mass spectrometers. Their instrumentation is based, in part, on the research of B. French at the University of Toronto Institutue for Aerospace Studies (UTIAS).

In the early 1980s, SCIEX developed the first commercial instrumentation for inductively coupled plasma-mass spectrometry (ICP-MS), a technique that now defines the performance limits for trace elemental analysis. They have also been at the forefront in the development of atmospheric pressure ionization and ion spray mass spectrometry for biomolecular applications. Their products are distributed worldwide through joint ventures with British Aerospace and Perkin-Elmer Corporation.


Inorganic Chemistry

Inorganic chemistry traditionally was concerned with the behaviour of chemical elements excluding carbon. Compounds based largely on carbon provided the basis for organic chemistry, but the boundary between inorganic and organic chemistry has become blurred. For example, a rapidly expanding field is organometallic chemistry which, being concerned with compounds containing metal atoms bound to one or several carbon atoms, bridges the 2 disciplines.

In the early development of chemistry, inorganic chemistry included characterization of elements and the measurement of their physical properties (eg, boiling point, density); however, the main current concern of inorganic chemists is the chemical reactions that elements in combination undergo, and the identification and study of new compounds.

In the early 20th century, the development of atomic theory made possible the organization of most information about the more common elements. From 1915 to 1940, inorganic chemistry developed more slowly. During WWII, however, it underwent a remarkable renaissance as a result of the need to understand the chemistry of uranium and other heavy elements, to separate the rare lanthanide elements (atomic numbers 57-71) and to determine their chemical behaviour (since these elements are formed in nuclear fission processes); to develop fully the chemistry of fluorine (since its high reactivity had previously limited its study), and to extend the chemistry of many other elements associated with the development of nuclear weaponry.

Facilities at Chalk River, Ont, played a part in those developments and Canadian NUCLEAR RESEARCH ESTABLISHMENTS have continued this research.

In its present form, inorganic chemistry aims to understand the importance of reaction conditions (eg, reaction temperature), and thus find means to prepare new combinations of elements. For example, many inorganic reactions may be greatly modified by the solvent medium; therefore, much research involves inorganic reactions in different solvents, both organic (eg, hydrocarbons, alcohol) and inorganic (eg, liquefied ammonia, liquid sulphur dioxide).

A second aim is to understand the detailed pathways by which reactions occur; a third, to determine the structure at the atomic level of the products of each reaction. Such structural information allows discussion of the binding forces that hold each molecule together.

In the 1970s and 1980s, considerable emphasis has been placed on aspects of inorganic chemistry related to the solid state and to compounds of the transition metals (eg, cobalt, platinum). Study of solid states has led to preparation of many new materials and to attempts to comprehend the electrical and mechanical properties of solids (relevant to the ELECTRONICS INDUSTRY and to the current interest in preparing new superconducting materials).

Transition metals form numerous organometallic derivatives, many of which catalyze other chemical reactions, eg, syntheses of important chemical fuels, such as methanol and the production of synthetic polymers.

Inorganic chemistry is particularly important to Canada's economy because of the significance of MINERAL RESOURCES. The development of Canada's extraction industries (eg, nickel, potash, lead, zinc, uranium) has involved the application of inorganic chemistry; however, Canada has been a significant contributor to the field mainly since the 1950s.

Significant work in the field includes pioneering studies on acids by R.J. Gillespie (McMaster), work on organometallic chemistry by H.C. Clark and W.A.G. Graham, and X-ray diffraction studies of inorganic materials by J. Trotter (UBC). In 1962 N. Bartlett (UBC) showed that the so-called inert gases (now called noble gases) are not, in fact, inert but are capable of forming stable chemical compounds (eg, xenon tetrafluoride).

In 1965 A.D. Allen and C.V. Senoff, at U of T, showed that molecular nitrogen can be bound chemically to a metal atom, thus laying the foundation for much of the present intensive search for alternative economical routes to nitrogen fixation (which is of enormous significance to Canadian crop production).

Canadian inorganic chemists continue to be dominant contributors in a wide range of areas that are important to the country's development. Inorganic compounds are of paramount importance in the chemical industry, with eight of the top ten chemicals being inorganic compounds. In addition, inorganic compounds are indispensable as catalysts in the petrochemical industry and as components of automobile catalytic converters and emission control devices.

Inorganic compounds have important new uses in the fabrication of new solid state materials for use as semiconductors, advanced ceramics, nonlinear optics and in the production of thin metal film coatings. The pharmaceutical industry and medicine also depend heavily on the inorganic chemist.

Not only are inorganic catalysts important in the sythesis of new drugs, but they are also used directly in the treatment of Alzheimer's, cancer, arthritis and other diseases, and as radiotracers in the diagnosis of diseases. Indeed there is now a whole area, bioinorganic chemistry, that studies the importance of inorganic chemistry in biological systems.

Inorganic compounds have a pivotal role in processes such as oxygen storage and transport, photosynthesis, and digestion of proteins and electron transfer, to name a few. In 1983 the Nobel Prize in Chemistry was awarded to Henry TAUBE, a Canadian-born and -educated chemist, for his work on electron transfer reactions.


Organic Chemistry

The isolation of products from animal and plant fluids and tissues has interested humans since antiquity. Few pure substances were identified before the 19th century. Animal and plant products are extremely complex mixtures of largely nonvolatile molecules. Because these substances were derived from living organisms, those involved in investigating them were called organic chemists. The different materials that could be isolated all contained the element carbon.

During the 19th century, the inventory grew rapidly of organic compounds that could be isolated in high purity, either directly (as naturally occurring products) or as derivatives (of their thermal or chemical degradation). The carbon content was found to vary greatly among them, and the most common other elements were hydrogen, nitrogen and oxygen. Sulphur and phosphorus also were often present but other elements occurred rarely.

As both organic and inorganic (ie, mineral) reagents became available, the theory of organic chemistry developed rapidly. It became apparent that products from natural sources and related new substances could be synthesized from nonliving sources, using increasingly well-understood reaction pathways. These developments made possible an understanding of the molecular structures of organic compounds and their reaction properties.

Complex organic molecules owe their existence to a strong tendency for carbon atoms to share their electrons with other atoms, in strong, direct covalent bonds. This property is the source of the molecular structures that comprise the largest part of dry living matter, and of the over one million man-made synthetic compounds developed over the past century.

The chemical manipulation of hydrocarbon molecules, derived mainly from petroleum, has given rise to such indispensable items as synthetic plastics, resins, fibres, rubbers, adhesives, paints, detergents, pesticides and explosives.

The wide range of prescription drugs of the modern pharmaceuticals industry owe their existence to the knowledge and skills of organic chemists. Organic chemistry has also made major contributions to human pleasure, eg, through dyes, colour photography, perfumes, flavours and sweetening agents.

As a result of the continually increasing and widespread use of its basic principles, organic chemistry in the 20th century has become a mainstay of other scientific disciplines, both within and outside the field of chemistry. Indeed the processing of animal and plant tissues and studies of biological transformations have passed to new disciplines including BIOCHEMISTRY, Pharmacology, DIETETICS and MOLECULAR BIOLOGY.

Nevertheless, although the field has become only marginally concerned with living matter, the term lives on to describe activities that concentrate on the chemistry of carbon-containing compounds. The term "bio-organic chemistry" refers to efforts to use the theory of organic chemistry to imitate living processes. The power of modern synthetic organic chemistry is illustrated by the completion (1973) of the chemical synthesis of vitamin B12. Similar challenges continue to be met in laboratories throughout the world.

The technologies behind the space program have also had a revolutionary effect on organic chemistry. In recent decades, developments in computer science, electronics, detectors and materials have placed at the disposal of organic chemists an array of sophisticated instruments for separation, identification and structural analysis of matter.

In the case of living matter, such analysis raises moral issues which society, rather than organic chemists, biochemists, geneticists and microbiologists, will have to explore (seeBIOETHICS, GENETIC ENGINEERING).

Much notable work in Canada has been carried out on naturally occurring compounds. Perhaps the most significant discovery was that of INSULIN by F.G. BANTING, C.H. BEST, and J.B. COLLIP at U of T (1922). The early work on alkaloids by L.E. MARION and R.H.F. MANSKE at the National Research Council in Ottawa, the first laboratory synthesis of sucrose by R.U. LEMIEUX at the Prairie Regional Laboratory of NRC in Saskatoon (1953), the first synthesis of ABO and other human blood group determinants, also by Lemieux, at the U of A (1975) and the brilliant syntheses of many natural products by K. WIESNER at the University of New Brunswick all have received worldwide attention.

Gobind KHORANA, who won the Nobel Prize for Medicine in 1968 for his work on the genetic code, carried out his early work at the BRITISH COLUMBIA RESEARCH COUNCIL, Vancouver. Most recently Michael SMITH with the University of British Columbia shared a Nobel Prize for developing techniques to manipulate and determine the functions of segments of DNA.


Physical Chemistry

Physical chemistry begins with the measurement and calculation of the physical properties of atoms and molecules in the gaseous, liquid and solid states (phases). Physical chemists use these results to characterize systems in chemical equilibrium; to study the energy, rate and direction of chemical transformations; and to understand the atomic and molecular structure of matter. In contemporary physical chemistry, these goals are met through the study of chemical thermodynamics, SPECTROSCOPY, kinetics and theoretical chemistry.

Chemical Thermodynamics

Chemical thermodynamics involves the calculation of energy (measured as heat and work) and the evaluation of entropy (degree of randomness). When energy, entropy and chemical potential are known, physical chemists can characterize equilibria in reactions, in solutions and between phases.

Electrolysis, the formation of emulsions, the mechanism of transport through membranes and the description of adsorption on surfaces are a few examples of contemporary chemical problems that are treated using thermodynamics and statistical mechanics. The extension of thermodynamic principles to far-from-equilibrium systems (eg, biological systems with their highly ordered structures) has been successfully undertaken by physical chemists.


The energy of atoms and molecules is available in small packets called quanta, which are characteristic of the energy of electronic, vibrational and rotational motions. Each quantum is associated with a particular wavelength of electromagnetic radiation and appears as a distinct line in a spectrum.

Analysis of spectral lines in the visible and ultraviolet range has clarified the electronic structure of atoms and molecules; that of infrared spectra gives bond stretching and bending characteristics and, for simple molecules, bond lengths. X-ray crystallography permits the determination of nuclear positions even in very large molecules.

Chemical Kinetics

Chemical kinetics involves measurement and interpretation of the rates at which molecules, atoms, ions and radicals react to form new products. The effect of pressure, temperature, concentration of reactants and radiation allows kineticists to specify how reactions occur in terms of collisions, transition complexes, intermediates and reaction paths. The study of gas-phase reactions has provided insight about how energy is redistributed as the reaction progresses; indeed the role of the electronic, vibrational and rotational states involved can be examined.

Theoretical Chemistry

Theoretical chemistry involves using fundamental principles of PHYSICS and MATHEMATICS to create models for chemical processes. It is best known for its role in explaining chemical bonding. The laws of quantum physics are essential in interpreting and directing spectroscopic measurements. Similar contributions have been made in the evolution of models for kinetic studies, particularly for the redistribution of energy in elementary reactions.

With the aid of statistical mechanics, thermodynamic quantities (eg, specific heat) and transport properties (eg, viscosity) have yielded to theoretical interpretation. Computational chemistry began in the 1960s when large-capacity computers became available. Contemporary programs in quantum chemistry not only produce molecular orbitals and electronic energy levels but also provide a wide variety of molecular properties. Complex reaction schemes can be modelled, synthetic spectra can be produced and even properties of fluids can be calculated by computer programs.

Physical chemistry began to take shape in the 1870s when Willard Gibbs's thermodynamics treatise appeared. By the 1890s, electrochemistry was a major preoccupation of physical chemists, especially for industrial applications (seeMETALLURGY), and by the early 1900s physical chemists were deeply involved in the study of radioactivity.

The assimilation of results of work in other fields has continued and some ideas (eg, quantum theory) have changed the course of physical chemistry. Other ideas, such as nuclear-magnetic resonance and infrared spectroscopy, were nurtured and perfected by physical chemists and have emerged as essential tools in all chemical subdisciplines.

The past century has seen major Canadian contributions to this development of physical chemistry, from the thermodynamic work of William Lash MILLER in the 1890s to the calculations of how electrons move about in chemical reactions, which earned Rudolph Marcus a Nobel Prize in 1992.

The electrochemical innovations of T.L. WILLSON (calcium carbide production patent, 1893) and A.E. LeSueur (chlorine production for bleaching paper pulp, 1888) received worldwide application and provided the impetus for Canadian hydroelectric development and the pulp and paper industries.

This early interest in classical thermodynamics was furthered by Andrew GORDON (U of T), who carried out the first calculation of thermodynamic properties of triatomic molecules (1932), by the careful measurements of Otto MAASS on critical phenomena (1930s) and by the phase rule analyses of A.N. CAMPBELL (University of Manitoba, 1930s-60s).

The work of R. Scheissler and J.H. Ross in developing explosives, during WWII, and the more recent development of improved recovery processes for copper-nickel mining and for extraction of BITUMEN from oil sands are examples of Canadian applications of classical thermodynamics to industrial problems. The modern experiments and analysis of S.G. Mason (Pulp and Paper Institute, Montréal) for fluid and particle flow have received worldwide recognition.

Studies of radioactivity and atomic and nuclear structures came early to Canada, and the work of physical chemists, such as Ernest RUTHERFORD (on the atom) and Frederick Soddy (radioactivity) at McGill, led to Nobel prizes (in 1908 and 1921, respectively).

This interest evolved into contemporary expertise in radiation chemistry (the use of cobalt-60 gamma radiation in cancer therapy was developed first in Canada by Harold JOHNS), to isotope separation (by H.G. THODE) and isotope-labelling techniques in tracer work (by J.W.T. SPINKS) and into the nuclear power reactor CANDU. The pioneering contributions of E.W.R. STEACIE (NRC), Carl Winkler (McGill) and M. Polanyi (U of T) to gas phase and solution kinetics placed Canada in a position to develop a polymer industry (wartime products, such as synthetic rubber, were manufactured at Polysar, Sarnia).

This Canadian prominence in free radical chemistry and photochemistry has been carried forward by the conceptual contributions of J. POLANYI (U of T) and by experiments with photosensitized mercury carried out by H.E. GUNNING (U of A). Indeed, John Polanyi's observation of infrared chemiluminescence and its significance for chemical lasers was recognized by a Nobel prize in 1986. Another outstanding contribution of a Canadian to physical chemistry is the work of Gerhard Herzberg, whose exhaustive investigation of the spectroscopy of small molecules culminated in a Nobel Prize in 1971.

In looking to the future, the clearest trend in physical chemistry is the resurgence of interest in the complex chemistry of the liquid and solid phases. Certainly physical chemistry will also turn more and more to the study of biological processes. Computational chemistry must surely continue to expand, and with it will come the opportunity to develop and test theoretical models to do computer experiments.


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