Chemistry 1B - Lecture 1 House Rules Introductory Topics on Hybridization PDF

Course: Chemistry 1B (1.10203) I am Mr. Belly Asong and I am your Lecturer for this course, and I have been in the teaching profession for the last 22 years. Office Room: Science 1 Building, S-157 Consultancy Hour: 4:00 – 5:00 PM If you want to see me, knock on my door gent...

Course: Chemistry 1B (1.10203) I am Mr. Belly Asong and I am your Lecturer for this course, and I have been in the teaching profession for the last 22 years. Office Room: Science 1 Building, S-157 Consultancy Hour: 4:00 – 5:00 PM If you want to see me, knock on my door gently and then push it slowly. If the room is locked, that means I am out, otherwise, you may send your concern through my email. Email address: [email protected] 1  For your assessment grade; 15% - Assignments 15% - Tests 20% - Practicals 50% - Final Exam Textbook: You can use any organic chemistry books 2  Appeals: Appeals are only for the final exam and not for the internal marks. So before you go on holiday at the end of the semester, kindly confirm your internal marks from your tutor. Normally, I also publish your internal marks on our UPNG Moodle platform every end of the semester for vetting. 3  Lecture Notes, Assignments, Notices: Lecture Notes, Assignments, Notices, and other stuff about our course are posted on our UPNG Moodle platform now and then. Taking Videos: When taking lecture videos, please do it discretely. Most of the time I am distracted by cameras pointing directly at my face. Kindly point your camera to the lecture board. 4  On Personal Hygiene: Everyone is expected to observe “proper personal hygiene”. Always see to it that you come to our class wearing clean clothes and shoes. If you are sweating, stay outside a bit and cool down. Do not wear very strong perfume or come to class without taking a bath. Taking care of yourself is a way of giving respect to others and to yourself also. 5  On Laboratory time: During laboratory time, you are expected to wear a clean laboratory coat and shoes. It is also important that you have studied the practical procedure ahead of time so that you can finish the practical on time. We are also maintaining the policy of no eating, drinking, or chewing betel nuts inside the lab. 6  On Laboratory Marks: Your practical weighs 20% of your grade. The marks included are the following;  Attendance and participation – 30 marks  Scientific Report – 40 marks * Late submission will incur deductions 7  On Your Tests and Assignments: Normally, I am giving a test every fortnight. So expect that you will have a lot of things to study and learn. Studying organic chemistry is tough because of the many concepts and reactions to learn. You will need a lot of time to digest this information, so spend your time well. Your tests carry 15% of your grade and in a semester we may have a minimum of 3 tests. 8  On Your Tests and Assignments: Your assignments carry 15% of your grade and we may have also a minimum of 3 assignments this semester. There are due dates also when to submit your assignment. Your tutor will give you deductions if you submit your assignment late. Sacrifice, hard work, discipline, patience, and commitment are the keys to success in life. Just do your best always, and God will reward you in the end. 9  On Your Tutorial Group: A group – B group – C group – D group – * Never register your name to another group. This might cost your grade at the end of the semester. 10  The course will cover the following topics; Hybridization and Molecular Geometry Resonance, Organic Acids and Bases Aliphatic and Aromatic Hydrocarbon Chemistry Reactions of Aliphatic Hydrocarbons Chemistry of Aromatic Hydrocarbons Reactions of Organohalides Alcohols, Ethers & Epoxides Aldehydes and Ketones Carboxylic acids and their Derivatives 11  Introduction and Chemical Bonding 12  Introduction This second semester, you’re going to learn the organic part (Chemistry 1B) You have already covered the inorganic chemistry component last semester 1 In this semester 2, I expect that everyone will pay attention and do extra effort to understand this course Now let us take a look at what this course is about 13  Introduction What is organic chemistry, and why should you study this? The answers to these questions are all around us since every living organism is made of organic chemicals Examples are proteins that make up our skin, hair, and muscles The DNA that controls our genetic heritage 14  Introduction What is organic chemistry, and why should you study this? The foods that nourish us The medicines we take when we are sick The polymers that we used in vehicles, aircraft, boats, and many infrastructures The fuel that we are using to run our cars SUVs, airplanes, yachts, and many others The perfume we like, these are all organic 15  Introduction Historically and originally, organic chemistry was known as the study of chemical compounds found in living things Over time, this concept has had to be modified as many other compounds were synthesized by chemists in laboratories 16  Introduction The modern definition of organic chemistry is the study of carbon- containing compounds of which 10-20% of known organic compounds are found in living things 17  In enzymatic reactions… The enzyme (3-hydroxy-3-methyl-glutaryl-CoA reductase or HMGR or HMG-CoA reductase) shown here in the ribbon model, is the rate-controlling enzyme of the mevalonate pathway that catalyzes a crucial step in the body’s synthesis of cholesterol. Understanding how this enzyme function has led to the development of drugs credited with saving millions of lives. 18 In Medicines 19  Why is carbon special? More than 50 million presently known chemical compounds, most of them contain carbon It is element number 6 and is in Period 2 and Group 4 in the Periodic Table It has 4 valence shell electrons and has an electronic configuration of 2,4 or 1s2, 2s2, 2p2 In forming a bond, it does not lose or gain electrons, it shares electrons – i.e. it forms covalent bonds 20  Chemical bonding To talk about a bond in a chemical sense is simply saying a linkage between two atoms A representation of this link is when one atom is ‘attached’ to another in a chemical compound In the simplest sense, this linkage comes in two ways:  Ionic bond, and  covalent bond 21  Ionic bond When there is a complete electron(s) transfer from one atom’s valance shell to another atom’s valance shell E.g. sodium chloride Na Cl Na Cl 22  Covalent bond But when two atoms equally share their valence shell electrons, the linkage is called the covalent bond E.g. methane and tetrafluorosilane H F C Si H F H F H F methane tetrafluorosilane 23  General rule As a general rule, when two non-metals bonds, the bond is a covalent bond When a metal and non-metal bond, it is an ionic bond But what about the covalent bond – how do they form and what brings it about 24  A short review of orbital Remember from your Chem 1A that, according to the quantum mechanical model, the behavior of a specific electron in an atom can be described by a mathematical expression called “wave equation” This is the same type of expression used to describe the motion of waves in a fluid, various physical systems, and electromagnetism 25  A short review of orbital The wave equation, also known as the Schrödinger equation, is a partial differential equation that describes how the wave function of a quantum system changes with time It was formulated by Austrian physicist Erwin Schrödinger in 1925 and is a central concept in quantum mechanics 26  A short review of orbital Specifically, in quantum mechanics, the behavior of subatomic particles, including electrons, is fundamentally different from the classical mechanics that govern larger objects like planets or billiard balls “Quantum mechanics uses wave functions to describe the probability of finding a particle in a given state or location”. 27  A short review of orbital The time-dependent Schrödinger equation for a single particle, like an electron, is given by; Ψ(x, t) = A * e^(i(kx - ωt)) "Psi of x, t equals A times e to the power of i times k times x minus omega times t" where: Ψ(x, t) is the wave function of the particle as a function of position (x) and time (t) A is a normalization constant e is the base of the natural logarithm i is the imaginary unit (√(-1)) k is the wave vector, related to the momentum of the particle ω is the angular frequency, related to the energy of the particle 28  A short review of orbital By plotting the square of the wave function (Ψ2) in three-dimensional space, an orbital can be defined as the three- dimensional probability distribution of an electron around a nucleus The square of the wave function (Ψ^2) gives the probability density of finding the electron at a specific position in space The higher the value of Ψ^2 at a particular point, the greater the likelihood of finding the electron there 29  A short review of orbital Hence, an orbital is essentially a visualization of the volume of space around the nucleus where an electron is most likely to be located It is important to note that orbitals do not represent fixed paths or trajectories like classical orbits but rather the areas where electrons are most probable to exist in accordance with the principles of quantum mechanics 30  A short review of orbital To better grasp the concept of orbitals and their probabilistic nature, envision them as resembling a photograph of an electron captured with a slow shutter speed This analogy highlights how orbitals represent the probability distribution of finding the electron in different regions around the atomic nucleus, akin to a blurred image, where the cloudier areas indicate higher probabilities 31  A short review of orbital This electron cloud doesn’t have a sharp boundary, but for practical purposes we can set the limit by saying that an orbital represents the space where an electron spends 90% to 95% of its time. 32  Back to Covalent bond  It is classified into two major types: Sigma (s) bonds and pi (p) bonds  The main difference between the two is the manner in which they are formed  Sigma bonds are formed when atomic orbitals overlap along the line joining the two bonded atoms (i.e. end-on/end-on overlap)  Here the electron distribution has an axial symmetry around the axis joining the two bonded nuclei 33  Covalent bond  The s bond is much, much stronger than the p bond because of the nature of the overlap end-on, end-on approaches s-bond  p bonds are formed by a side-on/side-on overlap of the unhybridized p-orbitals.  This overlap can only occur if the orbitals are parallel to each other as shown next 34  Covalent bond A p-bond side-on, side-on approaches p-bond In order for a bond to form between two atoms, atomic orbitals have to overlap This is only possible when the overlapping orbitals are of similar energy 35  Electronic configuration All atoms on the periodic table have a certain electronic arrangement known as the electronic configuration The electron in each shell are placed in orbitals of differing energy levels Before overlapping happens, the valence shell orbitals of differing energy levels undergo a process called hybridization 36  Hybridization This process is essentially a mixing of electrons and the atomic orbitals to produce degenerate one (having same energy levels) called hybrid orbitals Now let’s take a closer look at carbon: Carbon is in Period 2 and Group 4 of the Periodic Table It has an atomic number of 6, which means that it has 6 electrons in total 37  Hybridization In the electron shell diagram, the arrangement is as follows: the first 2 electrons are placed in the first shell while next 4 are placed in the second shell 38  Hybridization  In each of these shells, there are atomic orbitals where these electrons are stored  Each of these orbitals is capable of only storing 2 electrons  The first shell has only one orbital (i.e. an s-orbital) and thus there are only 2 electrons found in there  The second shell has four atomic orbitals, an s-orbitals and three p-orbitals 39  Hybridization Electron shell configuration  The s- and p-orbitals have different C: K =2, L = 4 energy levels with the s having a lower C level than the p ones  The shape of these orbitals are given below: Spherical s orbital Dumb-bell shape of p orbital 40  Hybridization z z z z x x x x y y y y 2s orbital 2px orbital 2py orbital 2pz orbital Notice that the three p orbitals are perpendicular to one another and occupy the three axes (px, py, and Pz) 41