Acetyl chloride is an acid chloride derived from acetic acid. It belongs to the class of organic compounds called acyl halides, it is a colorless, volatile liquid. Acetyl chloride was first prepared in 1852 by French chemist Charles Gerhardt by treating potassium acetate with phosphoryl chloride; the reaction of acetic anhydride with hydrogen chloride produces a mixture of acetyl chloride and acetic acid: 2O + HCl → CH3COCl + CH3CO2H Acetyl chloride is produced in the laboratory by the reaction of acetic acid with chlorodehydrating agents such as PCl3, PCl5, SO2Cl2, phosgene, or SOCl2. However, these methods give acetyl chloride contaminated by phosphorus or sulfur impurities, which may interfere with the organic reactions; when heated, a mixture of dichloroacetyl chloride and acetic acid gives acetyl chloride. It can be synthesized from the catalytic carbonylation of methyl chloride, it arises from the reaction of acetic acid and hydrogen chloride. Acetyl chloride is not expected to exist in nature, because contact with water would hydrolyze it into acetic acid and hydrogen chloride.
In fact, if handled in open air it releases white "smoke" resulting from hydrolysis due to the moisture in the air. The smoke is small droplets of hydrochloric acid and acetic acid formed by hydrolysis. Acetyl chloride is used for acetylation reactions, i.e. the introduction of an acetyl group. Acetyl is an acyl group having the formula-C-CH3. For further information on the types of chemical reactions compounds such as acetyl chloride can undergo, see acyl halide. Two major classes of acetylations include the Friedel-Crafts reaction. Acetyl chloride is a reagent for the preparation of esters and amides of acetic acid, used in the derivatization of alcohols and amines. One class of acetylation reactions are esterification. CH3COCl + HO-CH2-CH3 → CH3-COO-CH2-CH3 + H-ClFrequently such acylations are carried out in the presence of a base such as pyridine, triethylamine, or DMAP, which act as catalysts to help promote the reaction and as bases neutralize the resulting HCl; such reactions will proceed via ketene.
A second major class of acetylation reactions are the Friedel-Crafts reactions. Acetic acid Acetyl bromide Acetyl fluoride Acetyl iodide International Chemical Safety Card 0210
Electronegativity, symbol χ, is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus; the higher the associated electronegativity number, the more an atom or a substituent group attracts electrons towards itself. On the most basic level, electronegativity is determined by factors like the nuclear charge and the number/location of other electrons present in the atomic shells; the opposite of electronegativity is electropositivity: a measure of an element's ability to donate electrons. The term "electronegativity" was introduced by Jöns Jacob Berzelius in 1811, though the concept was known before that and was studied by many chemists including Avogadro. In spite of its long history, an accurate scale of electronegativity was not developed until 1932, when Linus Pauling proposed an electronegativity scale, which depends on bond energies, as a development of valence bond theory.
It has been shown to correlate with a number of other chemical properties. Electronegativity cannot be directly measured and must be calculated from other atomic or molecular properties. Several methods of calculation have been proposed, although there may be small differences in the numerical values of the electronegativity, all methods show the same periodic trends between elements; the most used method of calculation is that proposed by Linus Pauling. This gives a dimensionless quantity referred to as the Pauling scale, on a relative scale running from around 0.7 to 3.98. When other methods of calculation are used, it is conventional to quote the results on a scale that covers the same range of numerical values: this is known as an electronegativity in Pauling units; as it is calculated, electronegativity is not a property of an atom alone, but rather a property of an atom in a molecule. Properties of a free atom include ionization electron affinity, it is to be expected that the electronegativity of an element will vary with its chemical environment, but it is considered to be a transferable property, to say that similar values will be valid in a variety of situations.
Caesium is the least electronegative element in the periodic table, while fluorine is most electronegative. Francium and caesium were both assigned 0.7. However, francium's ionization energy is known to be higher than caesium's, in accordance with the relativistic stabilization of the 7s orbital, this in turn implies that francium is in fact more electronegative than caesium. Pauling first proposed the concept of electronegativity in 1932 as an explanation of the fact that the covalent bond between two different atoms is stronger than would be expected by taking the average of the strengths of the A–A and B–B bonds. According to valence bond theory, of which Pauling was a notable proponent, this "additional stabilization" of the heteronuclear bond is due to the contribution of ionic canonical forms to the bonding; the difference in electronegativity between atoms A and B is given by: | χ A − χ B | = − 1 / 2 E d − E d + E d 2 where the dissociation energies, Ed, of the A–B, A–A and B–B bonds are expressed in electronvolts, the factor −1⁄2 being included to ensure a dimensionless result.
Hence, the difference in Pauling electronegativity between hydrogen and bromine is 0.73 As only differences in electronegativity are defined, it is necessary to choose an arbitrary reference point in order to construct a scale. Hydrogen was chosen as the reference, as it forms covalent bonds with a large variety of elements: its electronegativity was fixed first at 2.1 revised to 2.20. It is necessary to decide which of the two elements is the more electronegative; this is done using "chemical intuition": in the above example, hydrogen bromide dissolves in water to form H+ and Br− ions, so it may be assumed that bromine is more electronegative than hydrogen. However, in principle, since the same electronegativities should be obtained for any two bonding compounds, the data are in fact overdetermined, the signs are unique once a reference point is fixed. To calculate Pauling electronegativity for an element, it
Safety data sheet
A safety data sheet, material safety data sheet, or product safety data sheet is a document that lists information relating to occupational safety and health for the use of various substances and products. SDSs are a used system for cataloging information on chemicals, chemical compounds, chemical mixtures. SDS information may include instructions for the safe use and potential hazards associated with a particular material or product, along with spill-handling procedures. SDS formats can vary from source to source within a country depending on national requirements. A SDS for a substance is not intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational setting. There is a duty to properly label substances on the basis of physico-chemical, health or environmental risk. Labels can include hazard symbols such as the European Union standard symbols; the same product can have different formulations in different countries. The formulation and hazard of a product using a generic name may vary between manufacturers in the same country.
The Globally Harmonized System of Classification and Labelling of Chemicals contains a standard specification for safety data sheets. The SDS follows a 16 section format, internationally agreed and for substances the SDS should be followed with an Annex which contains the exposure scenarios of this particular substance; the 16 sections are: SECTION 1: Identification of the substance/mixture and of the company/undertaking 1.1. Product identifier 1.2. Relevant identified uses of the substance or mixture and uses advised against 1.3. Details of the supplier of the safety data sheet 1.4. Emergency telephone number SECTION 2: Hazards identification 2.1. Classification of the substance or mixture 2.2. Label elements 2.3. Other hazards SECTION 3: Composition/information on ingredients 3.1. Substances 3.2. Mixtures SECTION 4: First aid measures 4.1. Description of first aid measures 4.2. Most important symptoms and effects, both acute and delayed 4.3. Indication of any immediate medical attention and special treatment needed SECTION 5: Firefighting measures 5.1.
Extinguishing media 5.2. Special hazards arising from the substance or mixture 5.3. Advice for firefighters SECTION 6: Accidental release measure 6.1. Personal precautions, protective equipment and emergency procedures 6.2. Environmental precautions 6.3. Methods and material for containment and cleaning up 6.4. Reference to other sections SECTION 7: Handling and storage 7.1. Precautions for safe handling 7.2. Conditions for safe storage, including any incompatibilities 7.3. Specific end use SECTION 8: Exposure controls/personal protection 8.1. Control parameters 8.2. Exposure controls SECTION 9: Physical and chemical properties 9.1. Information on basic physical and chemical properties 9.2. Other information SECTION 10: Stability and reactivity 10.1. Reactivity 10.2. Chemical stability 10.3. Possibility of hazardous reactions 10.4. Conditions to avoid 10.5. Incompatible materials 10.6. Hazardous decomposition products SECTION 11: Toxicological information 11.1. Information on toxicological effects SECTION 12: Ecological information 12.1.
Toxicity 12.2. Persistence and degradability 12.3. Bioaccumulative potential 12.4. Mobility in soil 12.5. Results of PBT and vPvB assessment 12.6. Other adverse effects SECTION 13: Disposal considerations 13.1. Waste treatment methods SECTION 14: Transport information 14.1. UN number 14.2. UN proper shipping name 14.3. Transport hazard class 14.4. Packing group 14.5. Environmental hazards 14.6. Special precautions for user 14.7. Transport in bulk according to Annex II of MARPOL73/78 and the IBC Code SECTION 15: Regulatory information 15.1. Safety and environmental regulations/legislation specific for the substance or mixture 15.2. Chemical safety assessment SECTION 16: Other information 16.2. Date of the latest revision of the SDS In Canada, the program known as the Workplace Hazardous Materials Information System establishes the requirements for SDSs in workplaces and is administered federally by Health Canada under the Hazardous Products Act, Part II, the Controlled Products Regulations. Safety data sheets have been made an integral part of the system of Regulation No 1907/2006.
The original requirements of REACH for SDSs have been further adapted to take into account the rules for safety data sheets of the Global Harmonised System and the implementation of other elements of the GHS into EU legislation that were introduced by Regulation No 1272/2008 via an update to Annex II of REACH. The SDS must be supplied in an official language of the Member State where the substance or mixture is placed on the market, unless the Member State concerned provide otherwise; the European Chemicals Agency has published a guidance document on the compilation of safety data sheets. The German Federal Water Management Act requires that substances be evaluated for negative influence on the physical, chemical or biological characteristics of water; these are classified into numeric water hazard classes. WGK nwg: Non-water polluting substance WGK 1: Slightly water polluting substance WGK 2: Water polluting substance WGK 3: Highly water polluting substance This section contributes to a better understanding of the regulations governing SDS within the South African framework.
As regulations may change, it is the responsibility of the reader to verify the validity of the regulations mentioned in text. As globalisation increased and countries engaged in cross-border trade, the quantity of hazardous material crossing international borders a
A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed by the reception of a proton by a base—in other words, it is a base with a hydrogen ion added to it. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid; because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic. In summary, this can be represented as the following chemical reaction: Acid + Base ⇌ Conjugate Base + Conjugate Acid Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed that any compound that can transfer a proton to any other compound is an acid, the compound that accepts the proton is a base. A proton is a nuclear particle with a unit positive electrical charge. A cation can be a conjugate acid, an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is the viewpoint.
The simplest anion which can be a conjugate base is the solvated electron whose conjugate acid is the atomic hydrogen. In an acid-base reaction, an acid plus a base reacts to form a conjugate base plus a conjugate acid: Conjugates are formed when an acid loses a hydrogen proton or a base gains a hydrogen proton. Refer to the following figure: We say that the water molecule is the conjugate acid of the hydroxide ion after the latter received the hydrogen proton donated by ammonium. On the other hand, ammonia is the conjugate base for the acid ammonium after ammonium has donated a hydrogen ion towards the production of the water molecule. We can refer to OH- as a conjugate base of H2O, since the water molecule donates a proton towards the production of NH+4 in the reverse reaction, the predominating process in nature due to the strength of the base NH3 over the hydroxide ion. Based on this information, it is clear that the terms "Acid", "Base", "conjugate acid", "conjugate base" are not fixed for a certain chemical species.
The strength of a conjugate acid is directly proportional to its dissociation constant. If a conjugate acid is strong, its dissociation will have a higher equilibrium constant and the products of the reaction will be favored; the strength of a conjugate base can be seen as the tendency of the species to "pull" hydrogen protons towards itself. If a conjugate base is classified as strong, it will "hold on" to the hydrogen proton when in solution and its acid will not dissociate. On the other hand, if a species is classified as a strong acid, its conjugate base will be weak in nature. An example of this case would be the dissociation of Hydrochloric acid HCl in water. Since HCl is a strong acid, its conjugate base will be a weak conjugate base. Therefore, in this system, most H+ will be in the form of a Hydronium ion H3O+ instead of attached to a Cl anion and the conjugate base will be weaker than a water molecule. If an acid is weak, its conjugate base will be strong; when considering the fact that the Kw is equal to the product of the concentrations of H+ and OH.
A weak acid will have a low concentration of H+. The Kw divided by a low H+ concentration will result in a low OH- concentration as well. Therefore, weak acids will have weak conjugate bases, unlike the misconception that they have strong conjugate bases; the acid and conjugate base as well as the base and conjugate acid are known as conjugate pairs. When finding a conjugate acid or base, it is important to look at the reactants of the chemical equation. In this case, the reactants are the acids and bases, the acid corresponds to the conjugate base on the product side of the chemical equation. To identify the conjugate acid, look for the pair of compounds that are related; the acid–base reaction can be viewed in a before and after sense. The before is the reactant side of the after is the product side of the equation; the conjugate acid in the after side of an equation gains a hydrogen ion, so in the before side of the equation the compound that has one less hydrogen ion of the conjugate acid is the base.
The conjugate base in the after side of the equation lost a hydrogen ion, so in the before side of the equation, the compound that has one more hydrogen ion of the conjugate base is the acid. Consider the following acid–base reaction: HNO3 + H2O → H3O+ + NO−3Nitric acid is an acid because it donates a proton to the water molecule and its conjugate base is nitrate; the water molecule acts as a base because it receives the Hydrogen Proton and its conjugate acid is the hydronium ion. One use of conjugate acids and bases lies in buffering systems. In a buffer, a weak acid and its conjugate base, or a weak base and its conjugate acid, are used in order to limit the pH change during a titration process. Buffers have both non-organic chemical applications. For example, besides buffers being used in lab processes, our blood acts as a buffer to maintain pH; the most important buffer in our bloodstream is the carbonic acid-bicarbonate buffer, which prevents drastic pH changes when CO2 is introduced. This functions as such: CO 2 + H 2 O ↽ − − ⇀ H 2 CO 3 ↽
The Jmol applet, among other abilities, offers an alternative to the Chime plug-in, no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, the Sculpt mode. Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS 9. Jmol operates on a wide variety of platforms. For example, Jmol is functional in Mozilla Firefox, Internet Explorer, Google Chrome, Safari. Chemistry Development Kit Comparison of software for molecular mechanics modeling Jmol extension for MediaWiki List of molecular graphics systems Molecular graphics Molecule editor Proteopedia PyMOL SAMSON Official website Wiki with listings of websites and moodles Willighagen, Egon. "Fast and Scriptable Molecular Graphics in Web Browsers without Java3D". Doi:10.1038/npre.2007.50.1
Occupational safety and health
Occupational safety and health commonly referred to as occupational health and safety, occupational health, or workplace health and safety, is a multidisciplinary field concerned with the safety and welfare of people at work. These terms refer to the goals of this field, so their use in the sense of this article was an abbreviation of occupational safety and health program/department etc; the goals of occupational safety and health programs include to foster a safe and healthy work environment. OSH may protect co-workers, family members, employers and many others who might be affected by the workplace environment. In the United States, the term occupational health and safety is referred to as occupational health and occupational and non-occupational safety and includes safety for activities outside of work. In common-law jurisdictions, employers have a common law duty to take reasonable care of the safety of their employees. Statute law may in addition impose other general duties, introduce specific duties, create government bodies with powers to regulate workplace safety issues: details of this vary from jurisdiction to jurisdiction.
As defined by the World Health Organization "occupational health deals with all aspects of health and safety in the workplace and has a strong focus on primary prevention of hazards." Health has been defined as "a state of complete physical and social well-being and not the absence of disease or infirmity." Occupational health is a multidisciplinary field of healthcare concerned with enabling an individual to undertake their occupation, in the way that causes least harm to their health. Health has been defined as It contrasts, for example, with the promotion of health and safety at work, concerned with preventing harm from any incidental hazards, arising in the workplace. Since 1950, the International Labour Organization and the World Health Organization have shared a common definition of occupational health, it was adopted by the Joint ILO/WHO Committee on Occupational Health at its first session in 1950 and revised at its twelfth session in 1995. The definition reads: "The main focus in occupational health is on three different objectives: the maintenance and promotion of workers’ health and working capacity.
The concept of working culture is intended in this context to mean a reflection of the essential value systems adopted by the undertaking concerned. Such a culture is reflected in practice in the managerial systems, personnel policy, principles for participation, training policies and quality management of the undertaking." Those in the field of occupational health come from a wide range of disciplines and professions including medicine, epidemiology and rehabilitation, occupational therapy, occupational medicine, human factors and ergonomics, many others. Professionals advise on a broad range of occupational health matters; these include how to avoid particular pre-existing conditions causing a problem in the occupation, correct posture for the work, frequency of rest breaks, preventative action that can be undertaken, so forth. "Occupational health should aim at: the promotion and maintenance of the highest degree of physical and social well-being of workers in all occupations. The research and regulation of occupational safety and health are a recent phenomenon.
As labor movements arose in response to worker concerns in the wake of the industrial revolution, worker's health entered consideration as a labor-related issue. In the United Kingdom, the Factory Acts of the early nineteenth century arose out of concerns about the poor health of children working in cotton mills: the Act of 1833 created a dedicated professional Factory Inspectorate; the initial remit of the Inspectorate was to police restrictions on the working hours in the textile industry of children and young persons. However, on the urging of the Factory Inspectorate, a further Act in 1844 giving similar restrictions on working hours for women in the textile industry introduced a requirement for machinery guarding. In 1840 a Royal Commission published its findings on the state of conditions for the workers of the mining industry that documented the appallingly dangerous environment that they had to work in and the high frequency of accidents; the commission sparked public outrage which resulted in the Mines Act of 1842.
The act set up an inspectorate for mines and collieries which resulted in many prosecutions and safety improvements, by 1850, inspectors were able to enter and inspect premises at their discretion. Otto von Bismarck inaugurated the first social insurance legislation in 1883 and the first worker's compensation law in 1884 – the first of their kind in the Western world. Similar acts followed in other countries
The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding environmental pressure. A liquid in a partial vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a higher boiling point than when that liquid is at atmospheric pressure. For example, water at 93.4 °C at 1,905 metres altitude. For a given pressure, different liquids will boil at different temperatures; the normal boiling point of a liquid is the special case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level, 1 atmosphere. At that temperature, the vapor pressure of the liquid becomes sufficient to overcome atmospheric pressure and allow bubbles of vapor to form inside the bulk of the liquid; the standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar.
The heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation. Evaporation is a surface phenomenon in which molecules located near the liquid's edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, resulting in the formation of vapor bubbles within the liquid. A saturated liquid contains as much thermal energy. Saturation temperature means boiling point; the saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase. The liquid can be said to be saturated with thermal energy. Any addition of thermal energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed.
A liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the vapor pressure of the liquid equals the surrounding environmental pressure. Thus, the boiling point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, or the IUPAC standard pressure of 100.000 kPa. At higher elevations, where the atmospheric pressure is much lower, the boiling point is lower; the boiling point increases with increased pressure up to the critical point, where the gas and liquid properties become identical. The boiling point cannot be increased beyond the critical point; the boiling point decreases with decreasing pressure until the triple point is reached. The boiling point cannot be reduced below the triple point. If the heat of vaporization and the vapor pressure of a liquid at a certain temperature are known, the boiling point can be calculated by using the Clausius–Clapeyron equation, thus: T B = − 1, where: T B is the boiling point at the pressure of interest, R is the ideal gas constant, P is the vapour pressure of the liquid at the pressure of interest, P 0 is some pressure where the corresponding T 0 is known, Δ H vap is the heat of vaporization of the liquid, T 0 is the boiling temperature, ln is the natural logarithm.
Saturation pressure is the pressure for a corresponding saturation temperature at which a liquid boils into its vapor phase. Saturation pressure and saturation temperature have a direct relationship: as saturation pressure is increased, so is saturation temperature. If the temperature in a system remains constant, vapor at saturation pressure and temperature will begin to condense into its liquid phase as the system pressure is increased. A liquid at saturation pressure and temperature will tend to flash into its vapor phase as system pressure is decreased. There are two conventions regarding the standard boiling point of water: The normal boiling point is 99.97 °C at a pressure of 1 atm. The IUPAC recommended standard boiling point of water at a standard pressure of 100 kPa is 99.61 °C. For comparison, on top of Mount Everest, at 8,848 m elevation, the pressure is about 34 kPa and the boiling point of water is 71 °C; the Celsius temperature scale was defined until 1954 by two points: 0 °C being defined by the wate