Introduction to Chemistry PDF

Dr/ Soha Ramadan Lecturer of pharmaceutical Chemistry ‫كلية الصيدلة بالجامعة المصرية الروسية معتمدة من الھيئة القومية لضمان جودة التعليم واإلعتماد‬  Pharmaceutical Organic Chemistry I PC102 Course aims for the theoretical part: Have extensive knowle...

Dr/ Soha Ramadan Lecturer of pharmaceutical Chemistry ‫كلية الصيدلة بالجامعة المصرية الروسية معتمدة من الھيئة القومية لضمان جودة التعليم واإلعتماد‬  Pharmaceutical Organic Chemistry I PC102 Course aims for the theoretical part: Have extensive knowledge on various classes of aliphatic compounds, their nomenclature, their synthesis, reactions and stereochemistry. Know the chemical and physical properties of various classes of aliphatic: such as Alkanes, Alkenes, Alkynes, Alkyl halides, Aromatic compounds Master various types of substitution, addition, and elimination reactions and be able to apply them for synthesis of vast amount of aliphatic and aromatic compounds. Understand various types of isomerism (Structural and Stereo), how to synthesize specific isomer. Study the effect of isomerism on the direction of chemical reactions Convert a given molecule into optically active one. 7 Tips for success in organic chemistry: Why study chemistry?  History of organic chemistry: The term “organic chemistry” was first used in about 1807, when Swedish chemist Jöns Jacob Berzelius introduced it to explain the study of compounds derived from the living resources available in nature. However, it was not until 1828 that German scientist Friedrich Wöhler experimented in laboratories with ammonium cyanate (an inorganic substance) and discovered that it could be converted into urea, an organic substance, through chemical processes. Through these experiments, he proved that organic matter could be synthesized in a laboratory without being linked to life, thus refuting Berzelius’s theory. Atoms, Element, Molecule and Compound:  Structure of atoms: Atoms are the fundamental components of matter, of three subatomic particles: protons, neutrons, and electrons. The structure of atoms determines the properties and behavior. Protons: Protons are positively charged. Found in the nucleus (central core) of an atom. Neutrons: Neutrons are neutral particles also located in the nucleus of an atom. But carry no charge (neutral). Electrons: Electrons are negatively charged particles that orbit around the nucleus in regions called electron shells or energy levels. They have a very small mass compared to protons and neutrons  Important items in Chemistry of elements: Atomic Number: equals the number of protons in the nucleus of the atom. The number of protons, which is always equal to the number of electrons in the neutral atom, is also the atomic number. Mass Number: The number of protons and neutrons combine to give us the mass number of an atom.  Isotopes: Isotopes are atoms with the same atomic number but different neutron numbers and thus different mass numbers.  The periodic table of elements The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic number. Mendeleev published his first version of the periodic table in 1869, today, with 118 known elements,  Electron Shell According to Bohr’s Atomic model electrons revolve around the nucleus in a specific circular path known as orbit or called a shell. Shells have stationary energy levels, the energy of each shell is constant. Each stationary orbit or shell is associated with a definite amount of energy. The greater the distance of the orbit from the nucleus, the more shall be the energy associated with it. These shells are called energy levels. It is numbered as 1, 2, 3, 4, ……. or K, L, M, N, ….. from the nucleus outwards.  Bohr’s Atomic model An electron shell may contain only a fixed number of electrons, each shell is associated with a particular range of electron energy, and thus each shell must fill completely before electrons can be added to an outer shell. Rules for determine valence of element: Try to solve these problems  Empirical, Molecular formula, Structural formula: There are three main types of chemical formulas: empirical, molecular and structural. Empirical formulas show the simplest whole-number ratio of atoms in a compound, molecular formulas show the number of each type of atom in a molecule, and structural formulas show how the atoms in a molecule are bonded to each other. Name Empirical formula Molecular Formula Structure formula Condensed formula H2O H2O H2O H2O CH3COOH CH2O C2H4O2 CH3COOH  Try to solve? Empirical Name formula Ethane Ethanol Propane Electron Shell: The quantum atomic model According to the quantum atomic model, an atom can have many possible numbers of orbitals. These orbitals can be categorized on the basis of their size, shape or orientation. A smaller sized orbital means there is a greater chance of getting an electron near the nucleus. The orbital wave function or ϕ is a mathematical function used for representing the coordinates of an electron. The square of the orbital wave function represents the probability of finding an electron. Types of Quantum Numbers: 1) Principal Quantum Number: Principal quantum numbers are denoted by the symbol ‘n’. They designate the principal electron shell of the atom. Since the most probable distance between the nucleus and the electrons is described by it, a larger value of the principal quantum number implies a greater distance between the electron and the nucleus 2) Orbital Angular Momentum Quantum Number):describes the shape of a given orbital. It is denoted by the symbol ‘l’ and its value is equal to the total number of angular nodes in the orbital. A value of the angular quantum number can indicate either an s, p, d, or f subshell which vary in shape. This value depends on (and is capped by) the value of the principal quantum number, i.e. the value of the azimuthal quantum number ranges between 0 and (n-1). The quantum atomic model 3) Magnetic Quantum Number The total number of orbitals in a subshell and the orientation of these orbitals are determined by the magnetic quantum number. It is denoted by the symbol ‘ml’. This number yields the projection of the angular momentum corresponding to the orbital along a given axis. The value of the magnetic quantum number is dependent on the value of (the orbital angular momentum) quantum number. For a given value of l, the value of ml ranges between the interval -l to +l. Therefore, it indirectly depends on the value of n. For example, if n = 4 and l = 3 in an atom, the possible values of the magnetic quantum number are -3, -2, -1, 0, +1, +2, and +3. The total number of orbitals in a given subshell is a function of the ‘l’ value of that orbital. It is given by the formula (2l + 1). For example, the ‘3d’ subshell (n=3, l=2) contains 5 orbitals (2*2 + 1). Each orbital can accommodate 2 electrons. Therefore, the 3d subshell can hold a total of 10 electrons. The quantum atomic model 4) Electron Spin Quantum Number The electron spin quantum number is independent of the values of n, l, and ml. The value of this number gives insight into the direction in which the electron is spinning, and is denoted by the symbol ms. The value of ms offers insight into the direction in which the electron is spinning. The possible values of the electron spin quantum number are +½ and -½. The positive value of ms implies an upward spin on the electron which is also called ‘spin up’ and is denoted by the symbol ↑. If ms has a negative value, the electron in question is said to have a downward spin, or a ‘spin down’, which is given by the symbol ↓. Spin Quantum Number, ms North South - N S - Electron aligned with Electron aligned against magnetic field, magnetic field, ms = + ½ ms = - ½ The electron behaves as if it were spinning about an axis through its center. This electron spin generates a magnetic field, the direction of which depends on the direction of the spin. Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 208 The Shape of s Orbitals: we can say that s-orbitals are spherically symmetric having the probability of finding the electron at a given distance equal in all the directions. The size of the s orbital is also found to increase with the increase in the value of the principal quantum number (n), thus, 4s > 3s> 2s > 1s.  The Shape of p Orbitals Each p orbital consists of two sections better known as lobes which lie on either side of the plane passing through the nucleus. The three p orbitals differ in the way the lobes are oriented whereas they are identical in terms of size, shape, and energy. As the lobes lie along one of the x, y or z-axis, these three orbitals are given the designations 2px, 2py, and 2pz. Thus, we can say that there are three p orbitals whose axes are mutually perpendicular. Similar to s orbitals the size, and energy of p orbitals increase with an increase in the principal quantum number (4p > 3p > 2p).  The Shape of d Orbitals The magnetic orbital quantum number for d orbitals is given as (- 2,-1,0, 1,2). Hence, we can say that there are five d-orbitals. These orbitals are designated as dxy, dyz, dxz, dx2–y 2 and dz2. Out of these five d orbitals, the shapes of the first four d-orbitals are similar to each other, which is different from the dz2 orbital whereas the energy of all five d orbitals is the same.  1A group # = # valence (outside) e- 8A 1 2A 3A 4A 5A 6A 7A 2 Row 3 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B = 4 # shells 5 6 s d p 7 6 7 f Electron Configuration 1s 1 group # row # # valence e- shell # possibilities are: possibilities are 1-7 s: 1 or 2 7 rows subshell p: 1-6 possibilities are d: 1-10 s, p, d, or f f: 1-14 4 subshells Total e- should equal Atomic # What element has an electron configuration of 1s1? Practice: Ask these questions every time you have to write an electron configuration Lithium: 1. find the element on the periodic table atomic # = 3 2. what is the period number? 2 3. how many shells? 2 4. what is the group number? 5. how many valence electrons? 1 6. what subshell(s) does Li have? 1 7. what is the electron configuration?s 1s2 2s1 General Rules Pauli Exclusion Principle Wolfgang Pauli Each orbital can hold TWO electrons with opposite spins. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem General Rules Aufbau Principle 6d 7s 5f 6d 5f 6p 7s Electrons fill the 5d 6s 4f 6p 5d lowest energy 4d 5p 6s 4f 5p orbitals first. 4p 5s 5s 4d 3d “Lazy Tenant 4s 4s 4p 3d 3p Rule” Energy 3s 3p 3s 2p 2s 2p 2s 1s 1s Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem General Rules Hund’s Rule Within a sublevel, place one electron per orbital before pairing them. “Empty Bus Seat Rule” WRONG RIGHT Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem  8 O Notation 15.9994 Orbital Diagram O 8e- 1s 2s 2p Electron Configuration 2 2 1s 2s 2p 4 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem  16 S Notation 32.066 Longhand Configuration S 16e- 1s2 2s2 2p6 3s2 3p4 Core Electrons Valence Electrons Shorthand Configuration S 16e- 2 [Ne] 3s 3p4 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem