Before we delve into learning about electrophiles and nucleophiles, let us quickly recall what an attacking reagent is. The species that attacks a substrate molecule or intermediate and forms a product is called an attacking reagent. It is of two types:
Electrophilic reagents or electrophiles
Nucleophilic reagents or nucleophiles
Thus, electrophiles and nucleophiles are those types of chemical species that either donate or accept electrons to form a new chemical bond. Moreover, the reaction mechanism occurring between electron donors and acceptors is best described by concepts of electrophile and nucleophile. These are the most important concepts in organic chemistry. They were introduced in the year 1933 and replaced the older terms, such as cationoid and anionoid.
Table of Contents
What Is Electrophile?
The word electrophile is made from “electro”, derived from electron and “phile”, which means loving.
Any molecule, ion or atom that is deficient in electrons in some manner can act as an electrophile. In other words, the reagent which attacks the negative of the molecule or loves electrons is called electrophile. They are generally positively charged or neutral species (electron-deficient molecules) with empty orbitals. Electrophiles can accept a couple of electrons.
Also Read: Electrophilic Substitution Reaction
Points to Remember:
They are electron deficient, and they tend to be attracted towards electrons.
They are either positively or neutrally charged.
They attack electron-rich areas such as carbon-carbon double bonds.
The movement of electrons is affected by the density, and the movement is generally from a high-density area to a low-density area.
Favour electrophilic addition and electrophilic substitution reactions.
They are also called Lewis acids because they accept electrons.
Electrophiles are involved in electrophilic substitution and addition reactions.
Types of Electrophiles
The different types of electrophiles can be classified as follows:
2. Neutral Electrophiles: They showcase electron deficiency.
(a) All Lewis acids: BF3, AlCl3, SO3, ZnCl2, BeCl2, FeCl3, SnCl2, CO2, SnCl4.
(b) The neutral atom that accepts electrons from the substrates:
> *C = O, R *COCl, R – * Mg – X, *I – Cl, CH3 – *CN, R*–Cl, R*–O,
The star (*) indicates the atom that accepts electrons.
(c) Free radicals, carbenes and nitrene act as electrophiles.
(d) Species with electrophilic centre:
Important information about electrophiles:
Hydronium ion carries a positive charge, but due to the presence of full vacant orbitals in its outer shell, it does not qualify to be an electrophile.
In the case of ammonium ion, it does not have vacant orbitals to attract electrons. So, ammonium ion is not classified as electrophiles.
What Is Nucleophile?
A nucleophile is a reactant which gives an electron pair to form a covalent bond. A nucleophile is usually charged negatively or is neutral with a lone couple of donatable electrons. H2O, -OMe or -OtBu are some examples. Overall, the electron-rich species is a nucleophile.
The word nucleophile is made from two words “Nucleo”, derived from the nucleus and “phile”, which means loving. Species that attack the positive side of the substrate or love the nucleus are called nucleophiles.
Nucleophiles donate unshared electron pairs, and they act as Lewis bases, according to Lewis notion of acids and bases.
Also Read: Nucleophilic Substitution Reaction
Points to Remember:
They consist of electrons and are attracted towards the nucleus. They are either negatively or neutrally charged.
They are donors of electrons.
Electrons move from low-density areas to high-density areas.
They support nucleophilic addition and nucleophilic substitution reactions.
They are also called Lewis bases.
Types of Nucleophiles
The different types of nucleophiles can be classified as follows:
1. Negatively Charged Nucleophiles:
2. All Lewis base which contain lone pairs:
The star (*) indicates the atom which donates electrons to the substrate.
3. Ambident Nucleophile:
Nucleophiles have two sites of electron-rich centre, or in which two or more atoms bear an unshared pair of electrons.
For example,
Resonating structures are also ambient nucleophiles.
4. Amphiphile Nucleophile: A molecule containing multiple bonds between carbon and a more electronegative atom can act both as electrophiles or nucleophiles.
For example,
Also Read: Electrophilic and Nucleophilic addition reaction
Difference between Electrophile and Nucleophile
To make you understand how electrophile and nucleophile are different from each other, here are some major differences between them:
ELECTROPHILE
NUCLEOPHILE
Accepts the electron pair
Supplies the electron pair
These can be either positively charged or neutral species
They can be either negatively charged or neutral species
Possess an empty orbital to receive the electron pair
Possess an electron pair which is loosely held and can be supplied easily
Attacks the points of high electron density
Attacks the point of low electron density
They are known as Lewis acids, as they can accept a pair of electrons
These are known as Lewis bases, as they can donate a pair of electrons
Forms an extra bond with the nucleophile
Increases its covalency by one unit
Example: All positively charged species such as H+, NO2+, electron-deficient species such as BF3, AlCl3
Example: All negatively charged species such as OH–, CN–, electron-rich species H2O, NH3
Solved Questions
Q1. Which of the following molecules and ions are electrophilic?
A CH4
B H2O
C Br(+)
D H2C=CH2
E BF3
F NO2(+)
G NH3
H Br(-)
Solution: C, E, F
Q2. Which of the following molecules and ions are nucleophilic?
A CH4
B H2O
C BH3
D H2C=CH2
E OH(–)
F Br(+)
G NH3
H Br(–)
Solution: B, D, E, G, H
Q3. Which of the following compounds is the best nucleophile?
NH3, CH3S−, CH3SH, H2O, CH3O−
Solution: CH3S−
Explanation: It is the best nucleophile because it has a negative charge (more electron density), and its electrons are held less tightly than those of CH3O− because sulphur is less electronegative than oxygen.
Q4. Which of the following is the strongest nucleophile?
CH3SeH, CH3OH, CH3SH, CH3TeH
Solution: CH3TeH
Explanation: Here, O, Se, S, and Te all belong to the same group 6. As we know, the size increases down the group; therefore, the electronegativity decreases. Due to this, the atoms can lose electrons more easily. So, there are stronger nucleophiles at the bottom of the group, and CH3TeH is the strongest nucleophile.
Q5. What will be the correct order of increasing the nucleophilic strength of the given compounds?
Solution: IV, I, III, II
Explanation: Here, two species are negatively charged, and the other two are neutral species. Negatively charged species are always more nucleophilic than neutral species. When water and ammonia are compared, the nucleophilic strength of ammonia is more than water because of the higher electronegativity of oxygen than nitrogen.
Lesser electronegativity will make electrons more readily available, therefore, a stronger nucleophile. Out of Cl− and F−, F− is a stronger nucleophile. This is exceptional to the expected trend. Fluoride ions would be expected to have less nucleophilic strength than chloride ions as the electronegativity of fluorine is more than chlorine. But the electron density of the chloride ion is more evenly distributed due to its bigger size hence is more stabilised as compared to the fluoride ion.
Therefore, the correct order will be IV, I, III, II.
Q6. Which of the following will be the strongest nucleophile in a nonpolar solution – I, Br, Cl, F?
Solution: F
Explanation: In non-polar solutions, nucleophilic strength increases with an increase in electronegativity. Here, Fluorine has the highest electronegativity. So, it is the strongest nucleophile.
Q7. The incorrect statement regarding a nucleophile is/are
1. A fluorine ion is an illustration of a nucleophile.
2. Weak acids are strong examples of strong nucleophiles.
3. A strong Arrhenius base is a strong nucleophile.
4. Nucleophiles tend to give electrons for the formation of a bond.
5. None of these.
Solution: None of these
Explanation: Nucleophiles are rich in electron species that can form bonding electrophiles
(electron-deficient species). Strong bases are strong nucleophiles. On the other hand, acids are generally weak nucleophiles.
Q8. The incorrect statement regarding the nucleophiles is /are
I. Negatively charged ions are the strongest nucleophiles.
II. The smaller the size of the molecule, the better is the nucleophile compared to the bigger ions.
III. In polar solvents, bigger atoms are bad nucleophiles.
Options:
1. I
2. II
3. II and III
4. III
5. All statements are correct
Solution: III
Explanation: In polar solvents, bigger atoms are good nucleophiles. The bigger the size of the atom, not the molecule, the better the nucleophile (I−>Br−>Cl−>F−). The radius of atoms increases down the group. Nucleophilic strength depends on the strength of the anion. For example, HI is a strong acid, and therefore, it has a weak conjugate base.
Frequently Asked Questions (FAQs)
Q1
What is the difference between electrophiles and nucleophiles?
Electrophiles are electron-deficient species. They are either positively charged or neutral species. Nucleophiles are electron-rich species. They are either negatively charged or neutral species. For example, NO2+, F–, Br–, Cl– CH3+
Q2
What is an electrophilic substitution reaction?
An electrophilic substitution reaction is a reaction in which a chemical group is displaced by an electrophile. Friedel Craft’s acylation and alkylation are popular examples of electrophilic substitution reactions.
Q3
What is meant by nucleophilic substitution reaction?
A nucleophilic substitution reaction is a reaction in which a nucleophile attacks an electron-deficient centre or an electrophile and displaces it. For example, alkyl bromide hydrolysis is an example of a nucleophilic substitution reaction.
Q4
Are alkenes nucleophiles or electrophiles?
Alkenes are electron-rich species and hence are nucleophiles.
Q5
Are alkanes nucleophiles or electrophiles?
Alkanes are neither nucleophilic nor electrophilic in nature. They are stable, unreactive molecules.
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Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations.
In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS".
He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.
CBSE Class 11 Chemistry Syllabus is a vast which needs a clear understanding of the concepts and topics. Knowing CBSE Class 11 Chemistry syllabus helps students to understand the course structure of Chemistry.
Unit-wise CBSE Class 11 Syllabus for Chemistry
Below is a list of detailed information on each unit for Class 11 Students.
UNIT I – Some Basic Concepts of Chemistry
General Introduction: Importance and scope of Chemistry.
Nature of matter, laws of chemical combination, Dalton’s atomic theory: concept of elements, atoms and molecules.
Atomic and molecular masses, mole concept and molar mass, percentage composition, empirical and molecular formula, chemical reactions, stoichiometry and calculations based on stoichiometry.
UNIT II – Structure of Atom
Discovery of Electron, Proton and Neutron, atomic number, isotopes and isobars. Thomson’s model and its limitations. Rutherford’s model and its limitations, Bohr’s model and its limitations, concept of shells and subshells, dual nature of matter and light, de Broglie’s relationship, Heisenberg uncertainty principle, concept of orbitals, quantum numbers, shapes of s, p and d orbitals, rules for filling electrons in orbitals – Aufbau principle, Pauli’s exclusion principle and Hund’s rule, electronic configuration of atoms, stability of half-filled and completely filled orbitals.
UNIT III – Classification of Elements and Periodicity in Properties
Significance of classification, brief history of the development of periodic table, modern periodic law and the present form of periodic table, periodic trends in properties of elements -atomic radii, ionic radii, inert gas radii, Ionization enthalpy, electron gain enthalpy, electronegativity, valency. Nomenclature of elements with atomic number greater than 100.
UNIT IV – Chemical Bonding and Molecular Structure
Valence electrons, ionic bond, covalent bond, bond parameters, Lewis structure, polar character of covalent bond, covalent character of ionic bond, valence bond theory, resonance, geometry of covalent molecules, VSEPR theory, concept of hybridization, involving s, p and d orbitals and shapes of some simple molecules, molecular orbital theory of homonuclear diatomic molecules(qualitative idea only), Hydrogen bond.
UNIT V – Chemical Thermodynamics
Concepts of System and types of systems, surroundings, work, heat, energy, extensive and intensive properties, state functions. First law of thermodynamics – internal energy and enthalpy, measurement of U and H, Hess’s law of constant heat summation, enthalpy of bond dissociation, combustion, formation, atomization, sublimation, phase transition, ionization, solution and dilution. Second law of Thermodynamics (brief introduction) Introduction of entropy as a state function, Gibb’s energy change for spontaneous and nonspontaneous processes. Third law of thermodynamics (brief introduction).
UNIT VI – Equilibrium
Equilibrium in physical and chemical processes, dynamic nature of equilibrium, law of mass action, equilibrium constant, factors affecting equilibrium – Le Chatelier’s principle, ionic equilibrium- ionization of acids and bases, strong and weak electrolytes, degree of ionization, ionization of poly basic acids, acid strength, concept of pH, hydrolysis of salts (elementary idea), buffer solution, Henderson Equation, solubility product, common ion effect (with illustrative examples).
UNIT VII – Redox Reactions
Concept of oxidation and reduction, redox reactions, oxidation number, balancing redox reactions, in terms of loss and gain of electrons and change in oxidation number, applications of redox reactions.
UNIT VIII – Organic Chemistry: Some basic Principles and Techniques
General introduction, classification and IUPAC nomenclature of organic compounds. Electronic displacements in a covalent bond: inductive effect, electromeric effect, resonance and hyper conjugation. Homolytic and heterolytic fission of a covalent bond: free radicals, carbocations, carbanions, electrophiles and nucleophiles, types of organic reactions.
UNIT IX – Hydrocarbons
Classification of Hydrocarbons Aliphatic Hydrocarbons: Alkanes – Nomenclature, isomerism, conformation (ethane only), physical properties, chemical reactions. Alkenes – Nomenclature, structure of double bond (ethene), geometrical isomerism, physical properties, methods of preparation, chemical reactions: addition of hydrogen, halogen, water, hydrogen halides (Markovnikov’s addition and peroxide effect), ozonolysis, oxidation, mechanism of electrophilic addition. Alkynes – Nomenclature, structure of triple bond (ethyne), physical properties, methods of preparation, chemical reactions: acidic character of alkynes, addition reaction of – hydrogen, halogens, hydrogen halides and water.
Aromatic Hydrocarbons:
Introduction, IUPAC nomenclature, benzene: resonance, aromaticity, chemical properties: mechanism of electrophilic substitution. Nitration, sulphonation, halogenation, Friedel Craft’s alkylation and acylation, directive influence of functional group in monosubstituted benzene. Carcinogenicity and toxicity.
To know the CBSE Syllabus for all the classes from 1 to 12, visit the Syllabus page of CBSE. Meanwhile, to get the Practical Syllabus of Class 11 Chemistry, read on to find out more about the syllabus and related information in this page.
CBSE Class 11 Chemistry Practical Syllabus with Marking Scheme
In Chemistry subject, practical also plays a vital role in improving their academic scores in the subject. The overall weightage of Chemistry practical mentioned in the CBSE Class 11 Chemistry syllabus is 30 marks. So, students must try their best to score well in practicals along with theory. It will help in increasing their overall academic score.
CBSE Class 11 Chemistry Practical Syllabus
The experiments will be conducted under the supervision of subject teacher. CBSE Chemistry Practicals is for 30 marks. This contribute to the overall practical marks for the subject.
The table below consists of evaluation scheme of practical exams.
Evaluation Scheme
Marks
Volumetric Analysis
08
Salt Analysis
08
Content Based Experiment
06
Project Work
04
Class record and viva
04
Total
30
CBSE Syllabus for Class 11 Chemistry Practical
Micro-chemical methods are available for several of the practical experiments. Wherever possible such techniques should be used.
A. Basic Laboratory Techniques 1. Cutting glass tube and glass rod 2. Bending a glass tube 3. Drawing out a glass jet 4. Boring a cork
B. Characterization and Purification of Chemical Substances 1. Determination of melting point of an organic compound. 2. Determination of boiling point of an organic compound. 3. Crystallization of impure sample of any one of the following: Alum, Copper Sulphate, Benzoic Acid.
C. Experiments based on pH
1. Any one of the following experiments:
Determination of pH of some solutions obtained from fruit juices, solution of known and varied concentrations of acids, bases and salts using pH paper or universal indicator.
Comparing the pH of solutions of strong and weak acids of same concentration.
Study the pH change in the titration of a strong base using universal indicator.
2. Study the pH change by common-ion in case of weak acids and weak bases.
D. Chemical Equilibrium One of the following experiments:
1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concentration of either of the ions. 2. Study the shift in equilibrium between [Co(H2O)6] 2+ and chloride ions by changing the concentration of either of the ions.
E. Quantitative Estimation i. Using a mechanical balance/electronic balance. ii. Preparation of standard solution of Oxalic acid. iii. Determination of strength of a given solution of Sodium hydroxide by titrating it against standard solution of Oxalic acid. iv. Preparation of standard solution of Sodium carbonate. v. Determination of strength of a given solution of hydrochloric acid by titrating it against standard Sodium Carbonatesolution.
F. Qualitative Analysis 1) Determination of one anion and one cation in a given salt Cations‐ Pb2+, Cu2+, As3+, Al3+, Fe3+, Mn2+, Ni2+, Zn2+, Co2+, Ca2+, Sr2+, Ba2+, Mg2+, NH4+ Anions – (CO3)2‐ , S2‐, NO2‐ , SO32‐, SO2‐ , NO ‐ , Cl‐ , Br‐, I‐, PO43‐ , C2O2‐ ,CH3COO‐ (Note: Insoluble salts excluded)
2) Detection of ‐ Nitrogen, Sulphur, Chlorine in organic compounds.
G) PROJECTS Scientific investigations involving laboratory testing and collecting information from other sources.
A few suggested projects are as follows:
Checking the bacterial contamination in drinking water by testing sulphide ion
Study of the methods of purification of water.
Testing the hardness, presence of Iron, Fluoride, Chloride, etc., depending upon the regional variation in drinking water and study of causes of presence of these ions above permissible limit (if any).
Investigation of the foaming capacity of different washing soaps and the effect of addition of Sodium carbonate on it.
Study the acidity of different samples of tea leaves.
Determination of the rate of evaporation of different liquids Study the effect of acids and bases on the tensile strength of fibres.
Study of acidity of fruit and vegetable juices.
Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with theapproval of the teacher.
Practical Examination for Visually Impaired Students of Class 11
Below is a list of practicals for the visually impaired students.
A. List of apparatus for identification for assessment in practicals (All experiments) Beaker, tripod stand, wire gauze, glass rod, funnel, filter paper, Bunsen burner, test tube, test tube stand, dropper, test tube holder, ignition tube, china dish, tongs, standard flask, pipette, burette, conical flask, clamp stand, dropper, wash bottle • Odour detection in qualitative analysis • Procedure/Setup of the apparatus
B. List of Experiments A. Characterization and Purification of Chemical Substances 1. Crystallization of an impure sample of any one of the following: copper sulphate, benzoic acid B. Experiments based on pH 1. Determination of pH of some solutions obtained from fruit juices, solutions of known and varied concentrations of acids, bases and salts using pH paper 2. Comparing the pH of solutions of strong and weak acids of same concentration.
C. Chemical Equilibrium 1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concentration of eitherions. 2. Study the shift in equilibrium between [Co(H2O)6]2+ and chloride ions by changing the concentration of either of the ions.
D. Quantitative estimation 1. Preparation of standard solution of oxalic acid. 2. Determination of molarity of a given solution of sodium hydroxide by titrating it against standard solution of oxalic acid.
E. Qualitative Analysis 1. Determination of one anion and one cation in a given salt 2. Cations – NH+4 Anions – (CO3)2-, S2-, (SO3)2-, Cl-, CH3COO- (Note: insoluble salts excluded) 3. Detection of Nitrogen in the given organic compound. 4. Detection of Halogen in the given organic compound.
Note: The above practicals may be carried out in an experiential manner rather than recording observations.
We hope students must have found this information on CBSE Syllabus useful for their studying Chemistry. Learn Maths & Science in interactive and fun loving ways with ANAND CLASSES (A School Of Competitions) App/Tablet.
Frequently Asked Questions on CBSE Class 11 Chemistry Syllabus
Q1
How many units are in the CBSE Class 11 Chemistry Syllabus?
There are 9 units in the CBSE Class 11 Chemistry Syllabus. Students can access various study materials for the chapters mentioned in this article for free at ANAND CLASSES (A School Of Competitions).
Q2
What is the total marks for practicals examination as per the CBSE Class 11 Chemistry Syllabus?
The total marks for the practicals as per the CBSE Class 11 Chemistry Syllabus is 30. It includes volumetric analysis, content-based experiment, salt analysis, class record, project work and viva.
Q3
Which chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry?
The organic chemistry chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry.
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