Fundamentals of Medicinal and Pharmaceutical Chemistry PDF

Fundamentals of Medicinal and Pharmaceutical Chemistry FUNCHEM.6 Ionic Bonding and the "electrolyte status" of body fluid D r. R o s h a n D e e n  General Chemistry - The...

Fundamentals of Medicinal and Pharmaceutical Chemistry FUNCHEM.6 Ionic Bonding and the "electrolyte status" of body fluid D r. R o s h a n D e e n  General Chemistry - The Essential Concepts by Chang Recommended and Goldsby 7e Reading Section 9.1, 9.2, 9.4, 9.5 FUNCHEM.6 Ionic Bonding and the "electrolyte status" of body fluid 2 FUNCHEM.6 Learning outcomes Define ‘octet rule’ and recall ‘electronegativity’. Differentiate between ‘pure covalent’ and ‘polar covalent’ bonding. Explain ‘ionic bonding’ and ‘ionic character’. Predict whether a covalent, polar covalent or ionic bond will form based on a knowledge of electronegativity values. Loading… Explain the formation of ionic compounds using electronic configurations. Differentiate between ‘electrolytes’ and ‘non-electrolytes’ and recall principal electrolytes in body fluids. Solve calculations regarding electrolyte concentrations in mEq/L. Explain the importance of electrolytes in the body and consequences of electrolyte overload or deficiencies (e.g. hypo or hyperkalemia and hypo or hypernatremia). FUNCHEM.6 Ionic Bonding and the "electrolyte status" of body fluid 3 Noble gas configuration Noble gases are chemically stable (chemically inert). They share a common e- configuration of 8 valence electrons that is very stable. He is an exception with 2 e-. 4  Octet Rule An atom other than hydrogen tends to form bonds until it is surrounded by eight valence electrons Atoms are most stable if they have a filled or empty outer shell of electrons. Except for H and He, a filled outer shell contains 8 valence e-. Atoms will: order elements will gain or loss et in Loading… gain or lose electrons (ionic) share electrons (covalent) and Octet (8) to become Stable to achieve a noble gas configuration. 5 Chemical bonds too much Ionic bond primary type) require energing An ionic bond is the electrostatic force that holds the cations and anions in an ionic compound. Atoms either completely lose one or more e- to become positive cations or gain one or more e- to become negative anions. (give off or take) Watch the animation titled ‘Ionic vs Covalent Bonding’ on the VLE 6 Chemical bonds Covalent Shareef) A covalent bond is formed when atoms share one pair of electrons Neither atom is willing to give up e- or is strong enough to take e- away. H - If ↓ they share these 2 electrons. Watch the animation titled ‘Ionic vs Covalent Bonding’ on the VLE 7  Ionic vs Covalent How do you know whether an ionic or covalent bond will form? Knowing the electronegativity of individual atoms can help determine the type of interaction between atoms Electronegativity values can be used to distinguish between covalent, polar covalent and ionic bonds Electronegativity is the ability of an atom to attract toward itself the electrons in a chemical bond. – Recall from FUNCHEM.3 8 Electronegativity marseecksnegativity The ability of an atom in a molecule to attract towards itself more attraction. electrons in a chemical bond Electronegativity the same, electrons shared equally. H2, N2, O2. Leually strong) One atom more electronegative than the other, e- not equally shared. H-F, H-Cl. δ+ H – F H–H δ- Non-polar Polar f as attract elections towards itS it slightly becomes () charged H will become slightly positive charge 9 Electronegativity trends (giveninname Pauling scale of relative electronegativity values 10 Types of chemical bonds most eles least Atoms of elements with widely X dec different electronegativity values I tend to form ionic bonds. Ionic - difference in electronegativity > 2.0 Loading… Polar covalent - difference in electronegativity 0.3 - 2.0 The most electronegative Pure covalent - difference in elements are the nonmetals electronegativity = 0. (Groups 5A–7A) and the least electronegative elements are the alkali and alkaline earth metals (Groups 1A–2A) – Ionic bonds 11 Types of chemical bonds is stable Hydrogen selections. with just Pure covalent – H2 and F2 ↑ H + H H H F + F FF or or H H F F E.N. [H] = 2.1 E.N. [H] = E.N. [F] = 4.0 E.N. [F] = 4.0 2.1 ∆E.N. = 4.0 – 4.0 = 0 ∆E.N. = 2.1 – 2.1 = 0 Pure covalent bond Pure covalent bond 12 Types of chemical bonds Polar covalent – H2O why don't Hydrogen cancel each other ?? H + O + H H O H since the sturture or isn't 00 H O H linear they won't cance each other δ- O – H δ+ ↑ 9 E.N. [O] = 3.5 E.N. [H] = 2.1 H H ∆E.N. = 3.5 – 2.1 = 1.4 Polar covalent bond 13 Ionic and ionic charcter no need to know how to calculate loss gained the. percentage - an e an e Lio + F Li + F 1s22s1 1s22s22p5 1s2 1s22s22p6 E.N. [Li] = 1.0 E.N. [F] = 4.0 ∆E.N. = 4.0 – 1.0 = 3 The greater the difference in Ionic bond electronegativity, the greater the ‘ionic character’ 14 Some salt for practice NaCl E.N. [Na] = 0.9 E.N. [Cl] = 3.0 ΔE.N. = 2.1 > - Ionic bond How does it happen ? oppo) 11Na : 1s22s22p6 3s1 a17Cl : 1s22s22p63s23p5 Removal of this e- gives a very stable configuration Requires an e- to give a very stable configuration [Na]+ : 1s22s22p6 [Cl]- : 1s22s22p63s23p6 A 3s electron from a sodium atom is transferred completely to a 3p orbital of a chlorine atom. 15 Calcium and oxygen Ca – O E.N. [Ca] = 1.00 E.N. [O] = 3.5 ΔE.N. = 2.5 4s2 - I 20Ca : 1s22s22p6 3s23p6 8O : 1s22s22p4 Removal of 2 e- gives a very Requires 2 e- to give a very stable configuration (noble stable configuration gas) [Ca]2+ : 1s22s22p6 3s23p6 [O]2- : 1s22s22p6 Two 4s electrons from a calcium atom are transferred completely to a 2p orbitals of the oxygen atom. 16 Properties of ionic compounds Ionic interactions take place between metal + non-metal metal and non-metal atoms. Can form lattice structures held together by electrostatic interactions. much energyhealt to. break the structure) Have high melting points. Leeds so Generally soluble in water. O W (disolves in water) 17  Electrolytes - ions in solution An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity (separate into charged will particles). exe NaCl > Na " Cl + changes > - ableto exeCHyCoot - Both weak electrolytes (separate partially) conduct dectricity be the ion -- as and strong electrolytes (separate fully) only 5% will exist - will dislocated more it will dissociated & conduct electricity laster - hydrgatic drag the - Nonelectrolytes do not conduct electricity with. it when dissolved in water (do not form charged sphere particles). Ions are hydrated in aqueous solution. This is the size of hydration the process by which ions are surrounded by sphere depends water molecules in a specific manner on the size of (Displayed to the right). When ions move their hydration spheres Na Y or. & water molecules move with them Electrolytes perform many important regulatory roles in our called hydration spheres bodies by virtue of their charged properties. 18 Water – Dipole Hydrogen don't cancel they E.N. = 2.1 cur they have a unique Oxygen δ- E.N. = 3.5 unusualangle (bend) O & Creation of a dipole - so if we cut it into half moment. Area of partial H H negative charge & area of δ δ one will always be greater. partial positive charge. + + - water have high density Bend (ro shaped) Lice have low density - needs high energy 19 Electrolytes in the body Cell e Blood K+, Mg2+, Na+. Na+, K+, Ca+, Mg+. HPO42-, proteins, SO42-, Cl-, HCO3-, proteins, HCO3-, Cl-. organic acids, HPO4-, SO42-. Interstitial fluid Na+, K+, Ca2+, Mg2+ Cl-, HCO3-, organic acids, HPO4-, SO42-. 20 Equivalents can be used to represent an amount of a charged substance how mouch charge present in the livid) is An equivalent of any substance is an amount of material that will give or react with an Avogadro's number of electrical charges - Weight Eq = Atomic or Molecular Weight/ n where n is the charge Examples Le = 1 mole 0 = 23 Na Na+ + e- 23g 6 x 1023 electrons molar mass An equivalent of Na+ isC 23g equiente - Aber of electrons Ca Ca2+ + O 2 e- = use this 40g 2 moles of electrons O An equivalent of Ca2+ is 20g Equivalents = (mass x valence) molar mass 21 In clinical situations Electrolyte status of the blood plasma or serum is measured. Results represented in different ways. In healthcare the most common representation of electrolytes is milliequivalents per litre mEq/L How many mEq in 1 Eq? 1000 mEq in 1 Eq 22 Importance of electrolytes Changes in the concentrations of sodium and potassium in blood can lead to serious medical emergencies Useful terms related to electrolyte disorders caliumin Blood High -emia “in the blood” es : calcemia -hypo a condition of low concentration hyper -hyper a condition of high concentration -natr represents sodium (Latin –natrium) -kal represents potassium (Latin –kalium) 23  Nervous system and electrolytes K+ and Na+ move in and out of channels in the membrane of nerve cell walls (some channels only permit K+ to pass through) Yust Net result – electrical signal amount of Nat Deficiencies in these ions can lead to serious problems that enter amount 2x5 Hypokalemia can lead to cardiac arrest. A diet low in K+ can of k + the exist lead to hypokalemia. You can read this short review to gain an insight into the importance of K+ ions in cardiac function and health. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3016067/pdf/ecc1 5e096.pdf 24 LoSalt – essential and deadly to Balance you inject a high KCl 40% more potassium in our bodies than consantration of Not since sodium. more k we have Potassium is found in all parts of the body. Red blood cells have most, followed by muscles & brain tissue. It is the main cationic electrolyte found inside cells. (t) 25 Deadly KCl If too much potassium outside the nerve cells, the potassium inside cannot escape and electrical impulse dies away. Potassium overdose paralyses the central nervous system, causes convulsions, diarrhoea, kidney failure and heart attack. In some countries condemned prisoners who agree to donate their organs for transplants may be executed by being given a ‘non-toxic’ lethal injection of potassium chloride. 26  Learning outcomes Define ‘octet rule’ and recall ‘electronegativity’. Recall and differentiate between ‘pure covalent’ and ‘polar covalent’ bonding. Explain ‘ionic bonding’ and ‘ionic character’. Predict whether a covalent, polar covalent or ionic bond will form based on a knowledge of electronegativity values. Explain the formation of ionic compounds using electronic configurations. Differentiate between ‘electrolytes’ and ‘non-electrolytes’ and recall principal electrolytes in body fluids. Calculate electrolyte concentrations in mEq/L. Explain the importance of electrolytes in the body and consequences of electrolyte overload or deficiencies (e.g. hypo or hyperkalemia and hypo or hypernatremia). 27 Thank you F O R M O R E I N F O R M AT I O N P L E A S E C O N TA C T D r. R o s h a n D e e n EMAIL: [email protected] 28