Category: Chemistry Notes PPT

Electricity is important for everyone. And nuclear power is the most controversial method or form of generating electricity. There are many experts who believe that evaluating the benefits of nuclear power plants should require a deliberate consideration of facts in terms of strategic, political, and emotional considerations. This should be done alongside the otherwise usual technical, environmental, and economic concerns that constitute the core elements of any technology that produces power. One should also focus on the nuclear power plant working principle.

It should be noted that according to statistics, nuclear energy almost provided 15% of the electricity that is generated across the globe. The plants where nuclear energy is produced are known as nuclear power plants. And nuclear power plants help in avoiding around 2.5 billion tonnes of CO₂ emissions. This fact shows that nuclear power is a step towards having a sustainable electricity supply for the world. It helps in achieving all sorts of goals in the domains of economics, environmental protection, and other vital capabilities.

Nuclear Fuel and the Nuclear Fuel Cycle

Now that we know what the nuclear power plant definition is, then students should remember that nuclear reactors need nuclear fuel for their proper functioning. And this nuclear fuel is often uranium. However, there are also other elements like plutonium that can be used as a substitute for uranium.

Thorium can also be turned into a proper isotope of uranium inside a nuclear reactor. This means that Thorium can also act as a nuclear fuel even though it is not classified as a nuclear fuel in the more straightforward sense.

It should be noted that Thorium occurs naturally just like uranium. But plutonium, on the other hand, is produced during a nuclear reaction. Hence, the main source of plutonium is a nuclear reactor.

One might find it interesting to note that uranium is present in seawater, most rocks, and is a rather common element that can be found in the crust of our planet. The abundance of uranium is also similar to that of molybdenum, beryllium, arsenic, germanium, and tin. It is also found in higher concentrations in some areas. And it is often these areas that act as suppliers of this particular element for nuclear power. This should give you a clear idea of what is a nuclear power plant and the nuclear power definition.

Now that students are familiar with nuclear fuel, the next important topic is the nuclear fuel cycle. The nuclear fuel cycle can be defined as the number of industrial processes that are considered together for the production of fuel for nuclear reactors and taking care of the spent fuel after it has been successfully removed from the reactor.

The nuclear fuel cycle begins when uranium is mined in different ores. The ore is also milled so that uranium can be extracted in the form of uranium oxide. This is done by processing large quantities of ore that are relatively low in terms of its quality. After that, that ore is crushed and grinded together so that uranium mineral particles can be extracted from it. Uranium in the form of a solution is captured from that. This is often done with sulfuric acid.

The next step consists of extracting uranium from the acid solution. This results in the formation of a solid oxide, which is also known as yellow cake. It is then packed into drums that are later sent for shipment to fuel manufacturing facilities located in different areas.

The Workings of a Nuclear Reactor and Nuclear Power Plant

Generating electricity inside a nuclear power plant working is not a simple process. But in this section, students can learn a basic overview of that process. To make matters simpler, students can think of the workings of a nuclear power plant meaning as being somewhat similar to plants that are powered by gas and coal to convert heat into electricity.

The only major difference in the case of power plants that are fired by fossil fuels is that they basically run on energy media that is extracted from oil, hard coal, and lignite. On the other hand, nuclear power plants utilize the heat that is given off when the nuclei of an atom split.

To help students understand this topic in a better manner, an image has been attached below. This image shows the workings of a nuclear power plant that has a pressurized water reactor model.

It should also be noted that the nuclear fission that occurs inside the reactor creates a lot of pressure. This pressure generates heat and this heats the water. The water eventually evaporates and it turns thermal energy into latent energy in the form of steam.

The steam that is under extreme pressure then drives the turbines. The turbines, in turn, move the generators that are connected to them to generate electrical energy. This is similar to a bicycle dynamo. When it comes to condensing the steam, then it is important for the turbines to drive by either using direct flow or seawater cooling. This is also possible by using a cooling system or a cooling tower. All of this should answer one’s question regarding how a nuclear power plant works.

Fun Facts About Nuclear Power

Did you know that nuclear power can be obtained from nuclear decay, nuclear fission, and nuclear fusion reactions? As of now, a large amount of energy is generated from nuclear power and that is made from the nuclear fission of uranium and plutonium.

Many experts also use the nuclear decay processes for niche applications, including radioisotope thermoelectric generators in several space probes like Voyager 2. A lot of international research is also focused on the area of electricity generation through fusion power.

Also, contrary to popular beliefs, nuclear power has one of the lowest fatalities levels per unit of energy that is generated. This is lower than the fatality rates for other energy sources. Petroleum, coal, hydroelectricity, and natural gas have been the cause of more fatalities per unit of energy due to accidents and air pollution.

Further, after the commercialization of nuclear power in the 1970s, it has prevented around 1.84 million deaths related to air pollution. The amount of carbon emission has also been reduced that would have otherwise resulted from the burning of fossil fuels.

This is not to say that there haven’t been disasters caused due to nuclear power plants. For example, the Chernobyl disaster in the Soviet Union that took place in 1986, the Three Mile Island accident in the United States of America in 1979, and the Fukushima Daiichi nuclear disaster that took place in Japan in 2011.

Because of these reasons, there is also a debate going on regarding nuclear power. There are several parties like Environmentalists for Nuclear Energy and the World Nuclear Association that deem nuclear energy to be a safe and sustainable form of energy that would reduce carbon emissions. But there are also organizations like NIRS and Greenpeace that hold firm on their belief that nuclear power poses several threats to both the environment and the people. The main question in the debate is regarding what is the main purpose of nuclear energy.

Omega 3 fatty acids are one of the essential fats that our body needs for various processes but cannot make from scratch. Our body gets omega 3 fatty acids from various foods. Foods which contain omega 3 fatty acids are cod liver oil, fish, vegetable oils, walnuts, flax seed oil and leafy vegetables. Benefits of omega 3 fatty acids include lower risk of cancer, prevention from cardiovascular disease and vital role in production of hormones that regulate blood clotting, inflammation etc. In this article we will discuss chemical aspects of omega 3 fatty acids in detail with health benefits for human beings. 

What are Omega 3 Fatty Acids?

Those polyunsaturated fatty acids which are characterized by the presence of a carbon – carbon double at the three atoms away from the terminal -CH3 (methyl group) in their carbon atom chain are called omega 3 fatty acids. 

Omega 3 fatty acids play a vital role in human physiology and lipid metabolism in animals. They are essential organic compounds and mammals can’t synthesize them, so mammals obtain it through their diet.  

Structure of Omega 3 Fatty Acid

Omega 3 fatty acid molecules possess multiple double bonds between carbon atoms. Each molecule of it must have a double bond between the 3rd and 4th carbon atoms from the end of the carbon atom chain. When the carbon atom chain of omega 3 fatty acids contain 18 or less carbon atoms then it is called ‘short chain omega 3 fatty acid’ while when the carbon atom chain of omega 3 fatty acids contain 20 or more carbon atoms then it is called ‘long chain omega 3 fatty acid’. Following three types of omega 3 fatty acids are essential for human physiology –

All these omega 3 fatty acids have either 3, 5 or 6 double bonds in a chain of 18, 20 or 22 carbon atoms respectively. Chain of fatty acids has two ends, one is carboxylic end (-COOH) while another one is methyl (-CH3) end. Carboxylic end is called the beginning of the chain or ‘alpha’ while the methyl end is called tail or ‘omega’ of the chain. Its molecular formula is C60H92O6 and molecular weight is 909.4 g.mol-1. 

Sources of Omega 3 Fatty Acids 

As our body can’t synthesize the omega 3 fatty acids and they are essential for us, so we have to include foods rich in omega 3 fatty acids in our diet. Sources of omega 3 fatty acids include fatty fishes, leafy vegetables, walnuts, seaweed and some types of algae, milk, blue eye cod, shark, broccoli, eggs, strawberry, kiwi, red meat, prawn, tuna, oysters, hemp and flax etc. Flax or commonly known as linseed is the best source of omega 3 fatty acid as it contains 11.4 grams of omega 3 per 85 grams of serving. Second best source of omega 3 fatty acids is hemp which contains 11 grams of omega 3 per 85 grams of serving.  Following fishes are also good source of omega 3 fatty acids –

• Mackerel 

• Salmon 

• Herring 

• Halibut 

• Tuna 

Although fish oils are a good source of omega 3 fatty acids but must be consumed very carefully as heavy metal poisoning in the body is a possible risk by consumption of fish oils. Refined Fish oils supplements contain traces of heavy metals like mercury, lead nickel etc. These get accumulated in our body with time and long – term consumption and cause heavy metal poisoning. The World health Organization has decided the acceptability standards of contaminants in fish oil. 

Benefits of Omega 3 Fatty Acids 

Omega 3 fatty acids are not only incredibly important for our body growth but for prevention of many diseases as well. Many evidences are available to support that omega 3 fatty acids are helpful in prevention and cure of heart diseases. Its few health benefits are listed below –

• Consumption of omega 3 fatty acids reduces the risk of cancer. Even evidence is available that omega 3 fatty acids are beneficial to people with advanced stages of cancer and cachexia. 

• They lower the blood pressure, hypertension and stimulate the blood circulation. 

• They are effective in lowering the inflammation. 

• They are helpful to relieve rheumatoid arthritis symptoms.

• They are helpful in physiological growth of the body. They are used in the treatment of autism, ADHD etc.

• They help in fighting against depression and anxiety.

• They can improve vision related problems. 

• They are effective against bipolar disorder. 

• They are mildly effective against cognitive problems so are used in the treatment of Alzheimer’s disease.

• Omega 3 supplements are effective against asthma attacks in children. 

• They are effective against metabolic syndrome, autoimmune diseases. 

• They are used in treatment of insomnia as well. 

This ends our coverage on the topic “Omega 3 Fatty acids”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions of NCERT Textbook problems based on this topic, then log on to website or download Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.

Ortho effect basically refers to the set of steric effects and some bonding interactions along with these polar effects that are caused by various substituents present in the given molecule. This ortho effect not only alters the chemical properties but along with it physical properties of the molecule are also altered. In general, the ortho effect is associated mainly with the substituted benzene compounds.

The Ortho effect is the process in which ortho-containing benzoic acids are reasonably stronger than benzoic acid. It doesn’t matter whether the substitute is electron-withdrawing or electron releasing. In simple words, a group in the ortho position constantly boosts the acid strength of an aromatic acid. In ortho meta and para substitutes, ortho compounds will be the strongest acid of all. A group present in the ortho position concerning the carboxyl group generates steric obstacles compelling the carboxyl group to rotate and step back from the benzene ring. After delocalization, a carboxyl group cannot participate in the ring resonance and so the acidity increases. 

Explanation of Ortho Effect 

The ortho effect is related to substituted benzene compounds. It refers to some bonding interactions and the set of steric effects with polar effects inflicted by multiple substituents in a given molecule modifying its physical and chemical properties.

There are three major ortho effects in substituted benzene.

Ortho Effect in Substituted Benzoic Acid

When a group is located at the ortho position to the carboxyl group is substituted benzoic said then the acidic property of that compound is more than benzoic acid. In most cases, ortho-substituted benzoic acid is stronger than para and meta isomers.

General Explanation

When a group is located at ortho to the carboxylic acid group in substituted benzoic acid, the steric constraints compel the carboxyl group to whirl out of the surface of the benzene ring. This shows the resonance property of the carboxyl group with the phenyl ring which boosts the acidity level of the carboxyl group which was curtailed because of destabilizing cross conjugation. This destabilizing cross conjugation is held responsible for lower acidity in benzoic acid.

The presence of hydrogen bonds near the carboxyl group can also trigger acidity.

Ortho Effect in Aniline

When a group is existing at the ortho position to NH2 in aniline, the basic nature of the compound becomes moreover less than aniline. To understand this properly, look on to the order of basicity of the following substituted aniline.

•  p-Aminophenol>Aniline>o-Aminophenol>m-Aminophenol

• Aniline>m-Nitroaniline>p-Nitroaniline>o-Nitroaniline

• P-Toluidine>m-Toluidine>Aniline>o-Toluidine

General Explanation

Due to steric obstacles, the protonation of substituted aniline is showcased. After protonation, the hybridization of nitrogen oxides alters in amino groups from sp² to sp³ propelling the group to be nonplanar. This influences the steric hurdles between the H atom of an amino group and the ortho-substituted group which makes the conjugate acid less stable, thus reducing the basicity of substituted aniline.

Ortho Effect in Electrophilic Aromatic Substitution

Ortho effect in electrophilic aromatic substitution of aromatic benzene compounds refers to the set of the steric effects that will determine the regioselectivity of an incoming electrophile in distributed benzene compounds. Here the meta directing group is meta to the ortho- para directing groups.

General Explanation 

When a particular meta directing group is meta to the ortho-para directing group. The group that comes will go ortho to the meta directing group rather than going para to the group. This is basically called the ortho effect. A good explanation for this ortho effect has not been provided but possibly we can say that there can be an intramolecular contribution from the available meta directing group. For a good explanation of this, we can take examples such as that of aromatic nitration of 1-methyl-3-nitrobenzene affords 4-methyl-1,2-nitrobenzene and 1-methyl-2,3-dinitrobenzene in yields 60.1% and 28.4% respectively.

You can observe similar results in the case of 3 methyl benzoic acid also.

Ortho Effect in Diels- Alder Reaction

In the normal electron demand Diels Alder reactions, the Z substituted dienophiles react with the 1-substituted butadienes to give 3,4-disubstituted cyclohexanes. These are independent of the nature of diene substitutes. This effect is also known as the ortho effect.

Ortho Effect- Things to Remember

• In the ortho effect, the basic strength decreases because of the electron-withdrawing groups or electron releasing groups that are placed on the ortho position.

• There is a point that ortho-substituted anilines are weaker as compared to the normal anilines irrespective of the fact that their nature is electron-withdrawing or electron releasing.

• The acidic property of a compound in which the group is at the ortho position to the carboxyl group is considered to be more than that of benzoic acid.

• Due to the ortho effect, animosity is considered to be a weaker base as compared to aniline.

• The relative basic strength of aniline can be represented as the: aniline> meta nitroaniline> para -nitroaniline> ortho nitroaniline.

• The relative basic strength of toluene can be mentioned as para toluidine>meta toluidine>aniline> ortho toluidine

Solved Examples

Which is More Acidic Para or Ortho Nitrophenol?

In para nitrophenol, there is no H-bonding due to attachment with neighboring carbon atoms. But in ortho nitrophenol, H bonding occurs due to attachment with adjacent atoms. That’s the reason why para nitrophenol is more acidic than ortho nitrophenol.

Why is Chlorine (CI) Ortho Para Directing?

The -I effect of chlorine takes out electrons from the benzene ring. This leads to the destabilization of intermediate carbocation created during electrophilic substitution. On the contrary, CI provides its lone pair of electrons to aromatic rings and increases the electron density at para and ortho positions. 

Conclusion

We have covered all the important points of the Ortho Effect that makes learning easy. We also covered solved examples.

The elements oxygen, sulphur, selenium, tellurium and polonium constitute group 16 elements of the periodic table. These are named as oxygen group elements after the name of the first member of the group. The oxygen group number is 16. The first four elements (oxygen, sulphur, selenium, and tellurium) of the 16th group are known as chalcogens. This is because many naturally occurring metal ores occur as oxides and sulphides. Group 16 elements are called chalcogens. 

The components having a place in Group 16 of the occasional table are portrayed by electron setups in which six electrons possess the peripheral shell. An atom having such an electronic design will in general, frame a steady shell of eight electrons by adding two more charges. This propensity to frame adversely charged particles, ordinary of nonmetallic components, is quantitatively communicated in the properties of electronegativity (the supposition of halfway bad charge when present in the covalent blend) and electron proclivity (the capacity of a nonpartisan molecule to take up an electron, shaping a negative particle).

 

Both these properties decline in force as the components expand in nuclear number and mass procedure down section 16 of the intermittent table. Oxygen has, with the exception of fluorine, the most elevated electronegativity and electron partiality of any component; the upsides of these properties then, at that point, decline strongly for the excess individuals from the gathering to the degree that tellurium and polonium are viewed as prevalently metallic in nature, having a tendency to lose instead of acquiring electrons in compound development.

 

Group 16 Elements

Oxygen is the most abundant of all elements. It occurs in the free form as an oxygen molecule and makes up 20.946% of the volume of the atmosphere. Most of it has been produced by photosynthesis. Oxygen makes up the major component of the earth crust. It occurs in the silicates mineral. It also occurs as metal oxide ores and deposits of oxo salts such as carbonates, sulphates, nitrates, and borates. As water, it comprises 89% by weight of the oceans. Oxygen occurs as ozone, an allotrope of oxygen in the upper atmosphere and is of great importance.

 

Sulphur- Sulphur is the non-metallic element and it is the sixteenth most abundant element found on the earth crust. It constitutes 0.03 – 0.1% by the mass of the earth’s crust. It occurs in the combined form of sulphides ores and sulphate ores. The other elements are comparatively rare. 

 

Selenium and tellurium are more electronegative than metals. Therefore, they occur as metal selenides and tellurides in the naturally occurring sulphide ores. Selenium and tellurium are found in anode mud or the anode slime deposited during the electrolytic refining of copper. 

 

General Characteristics of the Oxygen Group Elements

Similar to the case inside all gatherings of the table, the lightest component—the one of the littlest nuclear numbers—has outrageous or overstated properties. Oxygen, on account of the little size of its molecule, the modest number of electrons in its hidden shell, and the enormous number of protons in the core comparative with the nuclear range, has properties interestingly unique in relation to those of sulfur and the excess chalcogens. Those components act in an actually unsurprising and intermittent manner.

Albeit even polonium displays the oxidation state −2 in shaping a couple of parallel mixtures of the kind MPO (in which M is a metal), the heavier chalcogens don’t frame the negative state promptly, leaning toward positive states, for example, +2 and +4. Every one of the components in the gathering aside from oxygen might accept positive oxidation states, with the even qualities prevailing, yet the most noteworthy worth, +6, is certainly not a truly steady one for the heaviest individuals. At the point when this state is accomplished, there is a solid main thrust for the atom to get back to a lower state, frequently to the basic structure. This inclination makes compounds containing Se (VI) and Te (VI) more remarkable oxidizing specialists than S (VI) compounds. On the other hand, sulfides, selenides, and tellurides, in which the oxidation state is −2, are solid lessening specialists, effectively oxidized to the free components.

Neither sulfur nor selenium, and unquestionably not oxygen, frames absolutely ionic bonds to a nonmetal particle. Tellurium and polonium structure a couple of mixtures that are fairly ionic; tellurium (IV) sulfate, Te (SO₄)₂, and polonium (II) sulfate, PoSO₄, are models.

1. Electronic Configuration 

The elements of the oxygen family have six electrons in the outermost shell and have the general electronic configuration s ns² np⁴. The electronic configurations of the oxygen family are given below:

 

 

2. Atomic and Ionic Radii

The atomic and ionic radii of the elements of the oxygen periodic table group is smaller than that of the corresponding elements of group 15. The atomic radii and ionic radii of the group 16th elements is expected to increase on moving down the group. The comparatively smaller atomic and ionic radii of the oxygen group elements compared to group 15 elements are due to the increased effective nuclear charge of group 16 elements. Due to this, there is a greater attraction of the electrons by the nucleus and hence radii are less. The increase in the atomic radii of the 16th group elements, moving down the group is due to the increment in the number of electron shells.

 

3. Ionization Enthalpies

The ionization enthalpies of the elements of the oxygen family are less than those of the nitrogen family. On moving down the group from oxygen element to polonium element, the i
onization enthalpy or potential decreases.

 

The general trend of the ionization enthalpy is, it increases when we move from left to right. But when we move from the nitrogen group to the oxygen group the ionization enthalpy decreases. This happens because the nitrogen is completely half-filled p-orbitals. This half-filled configuration is stable because a half-filled and filled configuration has extra stability due to more exchange energy. But the configuration of oxygen is less stable and therefore, has less ionization enthalpy. However, it may be noted that the second ionization enthalpies (IE2) of the members of group 16 are higher than those of group 15. This is because, after the removal of the first electron, the second electron has to be removed from a more symmetrical half-filled configuration, which is more stable.  

 

4. Electronegativity

The elements of the 16^th group (chalcogen group) have higher values of electronegativity than the corresponding group 15 elements. The electronegativity decreases on going down the group. The decrease in electronegativity down the group is due to an increase in the size of the atoms.

 

5. Electron Gain Enthalpy

The oxygen family elements have high negative electron gain enthalpies. The value decreases down the group from sulphur to polonium. Oxygen exceptionally has low negative electron gain enthalpy. This characteristic is attributed to the small size of the oxygen atom so that its electron cloud is distributed over a small region of space and therefore, it repels the incoming electrons. 

 

One more component of the Group 16 components that equals drifts commonly displayed in sections of the occasional table is the expanding security of particles having the piece X (OH)n as the size of the focal molecule, X, increments. There is no compound HO―O―OH, wherein the focal oxygen particle would have a positive oxidation expression, a condition that it stands up to. The practically equivalent sulfur compound HO―S―OH, albeit not known in the unadulterated state, has a couple of stable subordinates as metal salts, the sulphoxylate. All the more profoundly hydroxylated mixtures of sulfur, S(OH)4 and S(OH)6, additionally don’t exist, not in view of sulfur’s protection from a positive oxidation state but instead due to the high charge thickness of the S(IV) and S(VI) states (the huge number of positive charges comparative with the little measurement of the atom), which repulses the electropositive hydrogen atoms, and the swarming that goes to the covalent holding of six oxygen molecules to sulfur, leaning toward loss of water.

As the size of the chalcogen molecule expands, the soundness of the hydroxylated intensifies builds: the compound orthotellurate corrosive, The (OH)₆, is fit for presence.

Did You Know?

• Oxygen is the second most electronegative element, the first being fluorine.

• Only sulphur is an element in the oxygen group that shows catenation property.

• All the group 16 elements exhibit allotropy.

In the entire universe, there is no such gas that possesses the properties of a perfect gas. An ideal gas law states the relationship between the pressure applied by a gas, the amount of gaseous substance, the absolute temperature of the gas, and the volume occupied by the gas. A gas that perfectly obeys the law of ideal gas is known as a perfect gas or general gas law. 

The ideal gas law, despite its limitations, is a good approximation of the behavior of many gasses in several conditions. The ideal gas law, developed by Benoit Paul Émile Clapeyron in 1834 stated that it’s a combination of the below laws:

• Empirical Charles’s law

• Boyle’s law

• Avogadro’s law

• Gay Lussac’s law

In short, the ideal gas law states that the product of one gram molecule’s pressure and volume is equal to the product of the gas’s absolute temperature and the universal gas constant.

Equation: PV=nRT

where,

Ideal Gas Equation Units

When using the gas constant R = 8.31 J/K.mol, we must enter the pressure P in pascals Pa, volume in m3, and temperature T in kelvin K.

When using the gas constant R = 0.082 L.atm/K.mol, pressure should be measured in atmospheres atm, volume measured in litres L, and temperature measured in Kelvin K.

The ideal gas law is based on Robert Boyle’s, Gay- Lussac’s, and Amedeo Avogadro’s observations. We arrive at the Ideal gas equation, which describes all of the relationships simultaneously, by combining their observations into a single formula.

The following are the three distinct expressions:

Boyle’s Law

Charle’s Law

Avagadro’s Law

When these 3 are combined it gives:

Volume is proportional to the number of moles and temperature, but inversely proportional to pressure, as shown by the equation above.

The following is a rewrite of this expression:

To get clear of the fraction, multiply both sides of the equation by P.

The ideal gas equation is depicted in the above equation.

Perfect Gas Law

The general perfect gas law is derived from the kinetic theory of gases. Its assumptions state that

• The volume of molecules is very small as compared to the volume that has been occupied by the gas

• The gas contains many molecules that move in random motion and obey Newton’s law of motion.

• Except during the elastic collision, there are no forces that act on the molecules.

No gas has only these properties. The behavior of the real gasses is closely studied by the perfect gas law at a very high temperature and low pressure when a maximum distance between the molecules and their high speeds moves ahead of this interaction. Gas will not obey the equation when the situation is such that the gas gets liquefied near its condensation point.

Types of a Perfect Gas

A perfect gas is simplified into two to more general perfect gases which are as follows:

1. Calorically Perfect Gas

Calorically perfect gas is the most restricted gas model that still gives accurate and reasonable calculations. For instance, if a compression stage of one model of the axial compressor is made having a variable, Cp and constant, Cv to compare the simplifications, then the derivation is found at a small order of magnitude. This gives a major impact on the final result Cp.

The expression of a calorically perfect gas is generalized as follows:

2. Thermally Perfect Gas

Thermally perfect gas is present in thermodynamics equilibrium. It does not react chemically. The functions of temperature are only applied in this case that are enthalpy, specific heat, and internal energy. This type of gas is generally used for modelling. For instance, if an axial compressor with limited temperature for fluctuations does not cause any significant deviations, then the heat capacity is still liable to vary only through temperature and the molecules are not allowed to disassociate.

e = e(T)h = h(T)de = CvdTdh = CpdT

Phenol is a common name for a compound. It is attached to a hydroxyl group to an atom number of an atomic ring.The IUPAC name of phenol is benzonal. The substitution of phenol with either the Ortho meta para or the numbering system can be employed. In either of the cases, the parent molecule is to be referred to as phenol. Common names and given to certain phenols for example phenols are known as cresols. Due to their high acidity, phenols are also known as carbolic acids.

Phenols are the organic compounds having benzene ring bonding to a hydroxyl group, which are also known as carbolic acids (phenol carbolic acid). Phenols usually react with active metals such as potassium, sodium and forms phenoxide. Happening such reactions of phenols with metals indicates it is acidic in nature.

 

Phenols also react with aqueous sodium hydroxide to produce phenoxide ions. It shows the acidity of phenols is higher compared to alcohol and water molecules as well.

 

Explaining the acidity of phenol

The acidity of phenol is because of its ability to lose the hydrogen ion forming phenoxide ions.

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Similarly, phenols can also lose H+ from the -OH group by showing acidic behavior.

()

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This phenoxide ion structure has a few special properties that are:

• Phenoxide ion is well established due to the resonance

• The oxygen is connected to sp² carbon, which has a high electronegativity.

So, the carbon will pull e^– from the oxygen. And, this makes the phenoxide ion stable due to the distribution of the electronegative charge. 

• Since the phenoxide ion is completely stable, phenol readily loses a hydrogen ion and shows the acidic character

• However, if any substituent is attached to the benzene ring, the stability of the phenoxide ion will be affected

Let’s look at the effect of substituents on the acidity of Phenols.

• If electron-donating groups are substituted on phenol, they push those electrons on the negative charged O. And, this reduces the phenoxide ion’s stability.

• So, if the electron-donating groups are substituted on phenol, resultantly, its acidity reduces. Due to this reason, cresol is less acidic than phenol.

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• But, if the electron-withdrawing groups are substituted with phenol, they pull the electrons from the negatively charged O, which increases the stability of the phenoxide ion.

• So, if the electron-withdrawing groups are substituted for phenol, it increases its acidity. Because of this, nitrophenol is more acidic than phenol.

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• Thereby, the position of the substituent group also affects the acidity of phenol. The substituent at ortho and para position has a more significant influence on acidity compared to the meta position. 

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• If a substituent is an EWG (Electron Withdrawing Group), delocalization of negative charge will be more when it lies in ortho and para position. So, EWG will cause an increased acidity rate when the group is at ortho and para positions compared to meta positions.

Resonance of Phenol

When more than one Lewis structure can be drawn, either the ion or the molecule is said to have resonance.

 

Resonance is a concept where electrons are delocalized over three or more atoms of a compound or molecule and the Lewis structure of that molecule cannot be depicted as a single and straightforward structure. 

 

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Observe that three of the four contributing structures possess a positive charge on the molecule’s oxygen atom. Therefore, the true hybrid structure must have a partial positive charge. Since oxygen is an electronegative element, the electrons in the oxygen-hydrogen bond orbital attract to the oxygen atom, resulting in partially positive hydrogen.

 

The loss of a hydrogen ion to a base creates a phenoxide ion, which is completely resonance stabilized.

 

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Also, observe that the phenoxide anion results upon the removal of hydroxy hydrogen by a base. This anion is resonance stabilized by delocalization of an electron pair all over the molecule, such as depicted by the contributing structures.

 

Properties of Phenol as an Acid

A few of the phenol’s properties by combining with different solutions are listed below.

The pH value of a typical dilute solution of phenol in water is approximately to be of 5 – 6 depending on its concentration. It means a very dilute solution is not really acidic enough to turn a litmus paper ultimately to red. Whereas litmus paper will be blue at pH = 8, and at the same time, red at pH = 5. If anything in between exists, it will be shown with some shade of “neutral.” Phenol reacts with the sodium hydroxide solution resulting in a colorless solution with sodium phenoxide.

 

During this reaction, the hydrogen ion was removed by the strongly basic hydroxide ion in the sodium hydroxide solution.

Phenol is not acidic enough to react with any of these. Going towards another approach, carbonate and hydrogen carbonate ions are not solid enough to remove a hydrogen ion from phenol. Unlike most acids, phenol does not give carbon dioxide when you mix it with one of them. In addition, this lack of reaction is quite useful. You can also recognize phenol because of the reasons listed below.

Physical Properties of Phenol Acidity

• Physical state: Phenols are colourless solids or liquids. However, due to oxidation they mostly turn reddish-brown in the atmosphere.

• Boiling point: An increase in the number of carbon atoms due to Van Der Waals forces, increases the boiling point of phenol.

• Solubility in water: Phenols are readily soluble in water due to their ability to form hydrogen bonding but the solubility decreases due to the addition of other hydrophobic groups and the ring.

• Reactions involv
  ing O–H bond cleavage: Phenols react with metals such as Na, K, and AI, etc with the release of hydrogen gas to form phenoxide.

Conclusion

This is all about the structural, physical, and chemical properties of phenol. Its unique properties due to the resonance of the constituent atoms of the molecule make it different. Focus on the conceptual description here and understand how it behaves in different chemicalreactions.