Why nitration of toluene is easier than benzene?

As you know from the structures of both the compounds that toluene has a methyl group on the benzene ring which is electron releasing group and hence activate the benzene ring by pushing the elctrons on the benzene ring. On the other hand nitro group on the benzene ring is electron withdrawing group which deactivates the benzene ring by withdrawing the electrons from the benzene ring . Now in the nitration attack of the nucleophile ( NO2 +) takes place. Hence reaction will takes place on that benzene faster which have more electron density on its ring which is the case of toluene.

Why is that the temperature of mono nitration of benzene be maintained at 50 degree Celsius?

So that only one NO2+ is substituted for the hydrogen on one of the carbons in benzene , if it was above 50 degree Celsius then more than one hydrogen would be substituted and mono nitration is only one substitution of hydrogen for NO2+

Why phenol have more intensity than benzene?

Because phenols have a lone pair of electron on the oxygen atom and this is drawn into the benzene ring thereby increasing the electron density of the ring which attracts more electrophiles.

IS chlorobenzene more reactive than benzene or not?

Chlorobenzene is less reactive than benzene as this group's -I effect( electron withdrawing effect) is more than its +R effect ( electron donating effect ) which in turn, actually decreases the electron density of the benzene ring and make the aromatic compound less reactive towards electrophiles.

Nitration of Methyl Benzoate

Benzene rings are components of many important natural products and other useful organic compounds. 
Therefore, the ability to put substituents on a benzene ring, at specific positions relative to each other, is a very 
important factor in synthesizing manyorganic compounds. The two main reaction types used for this are both 
substitutions: Electrophilic Aromatic Substitution (EAS) and Nucleophilic Aromatic Substitution (NAS). The 
benzene ring itself is electron-rich, which makes NAS difficult, unless there are a number of strongly electron-withdrawing substituents on the ring. EAS, on the other hand, is a very useful method for putting many different 
substituents on a benzene ring, even ifthere are other substituents already present. Electrophilic Aromatic 
Substitution chapter describes the factors involved in the regioselectivity for EAS reactions using benzene rings, 
which already have substituents on them. 
In this experiment you will put a nitro (—NO2) group on a benzene ring, which already has an ester group, 
attached to it (methyl benzoate). The actual electrophile in the reaction isthe nitronium ion (NO2+), which is 
generated in situ("in the reaction mixture" HNO3/H2SO4) using concentrated nitric acid and concentrated sulfuric 
acid. 

Reaction mechanism
The carbomethoxy group (-CO2CH3) directs the aromatic substitution reaction to the position that are meta to it. 
As a result the m-nitrobenzoate is the principal product from this reaction. Formation of dinitro products from this 
reaction is unlikely under the conditions in which you carryout your reaction. The reason for this is that both 
carbomethoxy groups as well as the nitro group (on the mono nitrated product)are deactivating groups making the 
second nitration less favorable. 

Concentrated sulfuric acid is the solvent for this reaction and is involved in the formation of nitronium ion (NO2+) 
from concentrated nitric acid. Water has a retarding effect on the nitration since it interferes with the nitric acid-sulfuric acid equilibrium (shown below) that generates the required nitronium ion 
Temperature also has an effect on the product distribution from this reaction. Higher the temperature, greater will 
be the amounts of dinitration products formed from this reaction. 
Safety Note
Caution:Avoid contact with the acids used in this experiment and the reaction product. 
Prevent contact with the skin, eyes, and clothing; work in the hood. An acid spill is 
neutralized using solid sodium carbonate or bicarbonate. The reaction is highly 
exothermic. A vigorous reaction will occur if the acid mixture is added too rapidly to the methyl benzoate. 
Concentrated nitric acid and concentrated sulfuric acid are both strong oxidizers, and strongly corrosive--wear gloves while handling them, and avoid breathing their vapors. 
Methyl benzoate and methyl m-nitrobenzoate are irritants-- wear gloves while handling them. Methanol is a flammable liquid,and is toxic -- no flames will be allowed in lab, 
wear gloves while handling it, and avoid breathing its vapors.

Experimental Procedure


Chemicals              Materials

                       150 – mL beaker 

Methyl benzoate        400-mL beaker 

Sulfuric acid (conc.)  125-mL flask 

Nitric acid (conc.)    Stirring rod 

Ice                    

Methanol              Suction filtrationfunnel 

In a 125-mL. Erlenmeyer flask mix 1.5 mL of methyl benzoate and approximately 4.0 mL of concentrated 
sulfuric acid (drop-wise), and chill it in an ice bath. Continue to cool the mixture in the ice bath to reduce the heat, 

which produced in the reaction. After complete addition of sulfuric acid, add approximately 2.0 mL concentrated 

nitric acid (measured in 10- mL graduated cylinder) drop- wise using a small graduated plastic pipette and mix by 
gentle swirling. Continue to cool the reaction mixture. Allow the reaction mixture to stand at room temperature for 
about five minutes. 
Float the 125-mL flask in a 400-ml beaker hot water bath. Remove the flask occasionally and swirl the content 
carefully. After fifteen minutes heating pour the reaction mixture in 100-ml ofice water contained in a 150- mL 
beaker, with stirring. 
Product Isolation- Isolate the product by vacuum filtration, wash the product with (ice) cold water (20 mL). 
Note- Proper washing removes the more soluble orthoisomer. The crude material may be purified by 
recrystallization from a small volume ( ~ 10 mL) of hot methanol (optional). The crude product is pressed dry. 
You may need to air dry (or hand dry using paper towels) the product. Discard the aqueous filtrate down the drain 
with lots of water. 

Synthesis of Methyl 3-nitrobenzoate  2
Notes: 
A.  The methyl benzoate is soluble in the sulfuric acid at this step and should produce a clear colorless solution. 
A yellow solution may indicate an unclean flask or an impurity introduced inadvertently. 
B.  For convenience, two or more students can share a larger batch of 50:50 conc. H2SO4and HNO3prepared in 
separately. 
C.  The nitration of methyl benzoate runs smoothly at nearly the rate that the HNO3is added. It is essential to 
keep the temperature within the specified limits, otherwise the yield falls; at 50°C the yield drops to about 
70%, while at 70°C the yield drops to about 50%. 
D.  It is not necessary to weigh the cracked ice. The density of cracked ice is about 0.5 g/mL. Hence, 15 grams 
of cracked ice is equivalent to about 30 mL. Do not take more ice than this because a filtration step comes 
after this and the presence of a large excess of ice will make the isolation of solid product more difficult. 
E.  The methanol wash will contain by-products of the reaction. These will include methyl 2-nitrobenzoate and 
traces of dinitrobenzbenzoic ester. There will also be some methyl 3-nitrobenzoateproduct in the methanol 
as well which will reduce your yield. The amount of this loss should be only a small percentage of your 
yield depending on your technique. Keep the methanol cold to minimize loss of your product. 
F.  Methanol has a bp 65°C so use a small beaker and an appropriate setting on the hot plate. Cover the small 
beaker with a small square of aluminum foil to reduce vapor loss as the methyl m-nitrobenzoate dissolves. 
Turn the hot plate off as soon as the methanol reachesboiling and a clear pale yellow solution is obtained. 
Place the hot flask on a paper towel on your desk, not directly on a cold surface.Also place a larger 
inverted beaker over the recrystallizing beaker to isolate cold drafts. Better crystals result when the hot 
solution cools slowly undisturbed. 
G.  The recrystallization of methyl 3-nitrobenzoate typically results in about a 15% loss of product compared to 
the yield at the crude product stage. This mechanical loss can be higher if you are careless in handling and 
leave significant solid on surfaces in the recrystallization procedure. 

Radical and Ion

Radicals and ions are reactive species. Both are produced from a neutral atom or a molecule that is more stable than an ion or a radical.

Radical

Radical is a species (atom, molecule) with an unpaired electron. In other words, they have an open shell configuration, and because of this, radicals are highly unstable, which leads to a high reactivity. Therefore, they are short lived. When radicals collide with another species, they tend to react in a way that leads to pairing of their unpaired electron. They can do this by obtaining an atom from another molecule. That atom will give the radical an electron to pair with its unpaired electron. However, due to this another radical is formed (the species who donated the atom to the previous radical will become a radical now). Another way a radical can react is by combining with a compound containing a multiple bond to produce a new larger radical. When a covalent bond is homolysed (the two electrons participating to make the bond are divided equally to the two atoms so that one atom gets only one electron), radicals are formed. Energy must be supplied to cause homolysis of covalent bonds. This is done in two ways, by heating or by irradiating with light. For example, peroxides produce oxygen radicals when they are subjected to heat. Normally when radicals are formed, they undergo a chain of reactions producing more and more radical. A chain reaction of a radical can be divided into three parts as initiation, propagation and termination. To stop a radical reaction (termination), two radicals should be joined together to form a covalent bond back. Radical reactions are important in many industrial processes. Radicals are used to produce plastics or polymers such as polythene. They are also important for the combustion processes by which the fuels are converted to energy. In living systems, radicals are always produced as intermediates in metabolism. However, radicals are considered as harmful within living systems. They can cause aging, cancer, atherosclerosis, etc. Therefore, in terms of medicine, radicals are also important.

Ion

Ions are charged species with a positive or a negative charge. Positively charged ions are known as cations and negatively charged ions are known as anions. When forming a cation, an electron from the atom is giving out. When forming an anion, an electron is obtained to the atom. Therefore, in an ion there is a different number of electrons than the protons. Ions can have -1 or +1 charges, which we call as monovalent. Likewise, there are divalent, trivalent, etc charged ions. Since cations and anions have opposite charges, they are attracted to each other with electrostatic forces, forming ionic bonds. Cations are usually formed by metal atoms, and the anions are formed by nonmetal atoms. For example, Sodium is a group 1 metal, thus forms a +1 charged cation. Chlorine is a nonmetal and has the ability to form a -1 charged anion.

What is the difference between Radical and Ion? • Ion is a species which has obtained an extra electron or donated an electron out. Radical is a species with an unpaired electron. • Ions have a positive or a negative charge. Radicals can have a positive, negative charge or no charge.

Crude Oil and Petroleum

Crude oil and petroleum are interchangeably used to indicate hydrocarbon fossil fuels. However, there is a difference in these two terms which is described below. Fuels are in high demand today, and it has become a very important factor in regulating world’s economy. Hydrocarbons contain so much energy, which is released when burning. This energy can be utilized to carry out lot of our daily functions. When hydrocarbon fuels are completely burning, carbon dioxide and water is produced. The increased consumption of petroleum fuels has caused many environmental problems too. Release of high level of carbon dioxide gas, which is a greenhouse gas, causes global warming. Carbon monoxide, carbon particles and other harmful gases are also released during the incomplete burning of fossil fuels. So, necessary steps should be taken to minimize the environmental pollution caused by these. Further, petroleum is a fossil fuel which should be used sustainably.

Petroleum

Petroleum is a mixture of hydrocarbons. This contains hydrocarbons with various molecular weights. These hydrocarbons may be aliphatic, aromatic, branched or unbranched. Petroleum is commonly used to indicate fossil fuel in gas, liquid and solid state. Hydrocarbons with a lower molecular weight (ex: methane, ethane, propane and butane) occur as gases. Heavier hydrocarbons like pentane, hexane and so on, occur as liquids and solids. Paraffin is an example for a solid hydrocarbon in petroleum. The proportion of each compound in petroleum differs from place to place.

Petroleum is a fossil fuel which has formed through millions of years under the earth’s surface. Dead animals, plants and other micro organisms are decayed and buried under sedimentary rock overtime. When these are subjected to heat and pressure over time, petroleum is formed. Though petroleum largely contains crude oil, some amount of natural gases may dissolve in it.

Petroleum reservoirs are largely found in Middle East countries. People recover petroleum through oil drilling. It is then refined and separated based on their boiling points. The separated petroleum products are used for various purposes. Alkanes from pentane to octane are used as petrol and nonane to hexadecane mixture is used as diesel, kerosene and jet fuel. Alkanes having more than 16 carbon atoms are used as fuel oil and lubricating oil. Heavier solid part of petroleum is used as paraffin wax. The smaller gas molecules are used for domestic and industrial purposes (for burners) by converting them to liquefied petroleum gas.

Crude Oil

Except the gas component in the petroleum, the rest of the mixture is known as crude oil. It is a liquid. Alkanes, cycloalkanes, aromatic hydrocarbons are mainly found in crude oil. There are other organic compounds containing nitrogen, oxygen, sulfur and other metals. The appearance of crude oil may differ due to the composition of it. Usually it is black or dark brown in color. Crude oil is refined, and its components are mainly used as fuels for automobile, machinery, etc.

What is the difference between Crude Oil and Petroleum? • The mixture of crude oil and natural gases is known as petroleum. • Natural gases are dissolved in crude oil, to make petroleum.

Electromagnetic Induction and Magnetic Induction

Electromagnetic induction and magnetic induction are two very important concepts in electromagnetic field theory. The applications of these two concepts are numerous. These theories are so important even the electricity would not be available without them. This article will discuss the difference between electromagnetic induction and magnetic induction.

What is Magnetic Induction?

Magnetic induction is the process of magnetization of materials in an external magnetic field. Materials can be categorized to several categories according to their magnetic properties. Paramagnetic materials, Diamagnetic materials and Ferromagnetic materials are to name a few. There are also some lesser common types such as anti-ferromagnetic materials and ferrimagnetic materials. Diamagnetism is shown in atoms with only paired electrons. The total spin of these atoms is zero. The magnetic properties arise only due to the orbital motion of electrons. When a diamagnetic material is placed in an external magnetic field, it will produce a very weak magnetic field antiparallel to the external field. Paramagnetic materials have atoms with unpaired electrons. The electronic spin of these unpaired electrons acts as small magnet, which is very stronger than the magnets created by the electron orbital motion. When placed in an external magnetic field, these small magnets align with the field to produce a magnetic field, which is parallel to the external field. Ferromagnetic materials are also paramagnetic materials with zones of magnetic dipoles in one direction even prior to the external magnetic field is applied. When the external field is applied, these magnetic zones will align themselves parallel to the field so that they would make the field stronger. Ferromagnetism is left in the material even after the external field is removed, but paramagnetism and diamagnetism vanishes as soon as the external field is removed

What is Electromagnetic Induction?

Electromagnetic induction is the effect of current flowing through a conductor, which is moving through a magnetic field. The Faraday’s law is the most important law regarding this effect. He stated that electromotive force produced around a closed path is proportional to the rate of change of the magnetic flux through any surface bounded by that path. If the closed path is a loop on a plane, the rate of magnetic flux change over the area of the loop is proportional to the electromotive force generated in the loop. However, this loop is not a conservative field now; therefore, common electrical laws such as Kirchhoff’s law are not applicable in this system. It must be noted that a steady magnetic field across the surface would not create an electromotive force. The magnetic field must vary in order to create the electromotive force. This theory is the main concept behind electricity generation. Almost all of the electricity, except from the solar cells, is generated using this mechanism.

What is the difference between electromagnetic and magnetic induction? • Magnetic induction may or may not produce a permanent magnet. Electromagnetic induction produces a current so that the generated current opposes the change in the magnetic field. • Magnetic induction only uses magnets and magnetic material, but electromagnetic induction uses magnets and circuits.

Paramagnetic vs Diamagnetic

Paramagnetic vs Diamagnetic  

Materials tend to show weak magnetic properties in the presence of an externally applied magnetic field. Some materials are attracted by the external magnetic field, whereas some are repelled by the external magnetic field. Due to this magnetic behaviour, elements and compounds can be categorized as two types, namely ‘paramagnetic’ and ‘diamagnetic’ Materials that are attracted by external magnetic fields are called ‘Paramagnetic’ and materials that are repelled by external magnetic fields are called ‘Diamagnetic’.

More on Paramagnetism

Paramagnetism occurs due to the presence of unpaired electrons in the system. Each element has a different number of electrons, and that defines its chemical character. According to how these electrons fill into the energy levels around the nucleus of the respective atom, some electrons are left unpaired. These unpaired electrons act as little magnets causing magnetic properties under the influence of an externally applied magnetic field. Actually, it’s the spin of these electrons that causesmagnetism.

Paramagnetic materials have permanent dipole magnetic moments due to the spin of the unpaired electrons even during the absence of an external magnetic field. But these dipoles orient themselves randomly due to thermal motion hence giving a zero net dipole magnetic moment. When an external magnetic field is applied, the dipoles tend to align in the direction of the applied magnetic field resulting in a net dipole magnetic moment. Therefore, paramagnetic materials are slightly attracted by the external magnetic field and the material does not retain magnetic properties once the external field is removed. Only a small induced magnetization is created even in the presence of an external magnetic field, and this is because only a small fraction of spins is oriented by the external magnetic field. This fraction is directly proportional to the strength of the field created.

Generally, higher the no. of unpaired electrons, higher the paramagnetism and higher the strength of the field created. Therefore, transition and inner transition metals show stronger magnetic effects due to the localization of ‘d’ and ‘f’ electrons and also due to the presence of multiple unpaired electrons. Some commonly known paramagnetic elements include Magnesium, Molybdenum, Lithium, and Tantalum. There are also stronger synthetic paramagnets such as ‘ferrofluids’.

More on Diamagnetism

Some materials tend to show a repelled magnetic behaviour when put in contact with an external magnetic field. These are said to be diamagnetic, and they create magnetic fields that are opposing in the direction to the external magnetic field and hence the repelling. Generally all materials have diamagnetic properties making a weak contribution to the magnetic behaviour of the material when subjected to an external magnetic field. But in materials that show other magnetic properties such as ‘paramagnetism’ and ‘ferromagnetism’, the effect of diamagnetism is negligible. Due to its weak magnetic property the effects of diamagnetism is difficult to observe. ‘Bismuth’ acts as a strong diamagnet.

What is the difference between Paramagnetism and Diamagnetism?

• Paramagnetic materials are attracted by external magnetic fields whereas diamagnetic materials are repelled.

• Paramagnetic materials have at least one unpaired electron in the system, but diamagnetic materials have all their electrons paired.

• The magnetic field created by paramagnetic materials are in the direction of the external magnetic field whereas the magnetic field created by diamagnetic materials are opposing in direction to the external magnetic field.

• Paramagnetism is a stronger magnetic behaviour exhibited only by selective materials, whereas diamagnetism is a weak magnetic behaviour generally shown by all materials and easily suppressed in the presence of stronger magnetic properties.

Continuous Spectrum and Line Spectrum

There are mainly two types of spectra as continuous and line spectra. Line spectra can be an absorption spectrum or an emission spectrum. Absorption and emission spectra of a species help to identify those species and provide a lot of information about them. When absorption and emission spectra of a species are put together, they form the continuous spectrum. An absorption spectrum is a plot drawn between absorbance and wavelength. Sometimes instead of wavelength, frequency or wave number can also be used in the x axis. Log absorption value or the transmission value is also used for the y axis in some occasions. Absorption spectrum is characteristic for a given molecule or an atom. Therefore, it can be used in identifying or confirming the identity of a particular species.

Atoms, ions, and molecules can be excited to higher energy levels by giving energy. The lifetime of an excited state is generally short. Therefore, these excited species have to release the absorbed energy and come back to the ground state. This is known as relaxation. The release of energy may take place as electromagnetic radiation, heat or as both types. The plot of released energy versus wavelength is known as the emission spectrum. Each element has a unique emission spectrum as they have a unique absorption spectrum. So radiation from a source can be characterized by emission spectra.

Continuous Spectrum

If all the wavelengths are present within a given limit, that is a continuous spectrum. For example, rainbow has the all seven colors and it is a continuous spectrum. Continuous spectra are formed when hot objects like stars, moons emit electromagnetic radiations at all the wavelengths.

Line Spectrum

As the name says, line spectrum has only few lines. In other words they have few wavelengths. For example, a colored compound is visible to our eyes in that particular color because it absorbs light from the visible range. Actually, it absorbs the complementary color of the color we see. For example, we see an object as green because it absorbs purple light from the visible range. Thus, purple is the complementary color of green. Likewise, atoms or molecules also absorb certain wavelengths from the electromagnetic radiation (these wavelengths are not necessarily to be in the visible range). When a beam of electromagnetic radiation passes through a sample containing gaseous atoms, only some wavelengths are absorbed by the atoms. So when the spectrum is recorded, it consists of a number of very narrow absorption lines. And this is an absorption line spectrum. It is characteristic to a type of atom. The absorbed energy is used to excite ground electrons to upper levels in the atom. Since the energy difference is discreet and constant, the same kind of atoms will always absorb the same wavelengths from the given radiation. When this excited electron is coming back to the ground level, it emits the absorbed radiation and it will form an emission line spectrum.

What is the difference between Continuous Spectrum and Line Spectrum? • Continuous spectrum contains all the wavelengths in a given range whereas line spectrum contains only few wavelengths. • Line spectra can be generated in absorption and emission. When both absorption and emission spectra of one species is put together, it forms a continuous spectrum.