Consumer Chemistry

Total Page:16

File Type:pdf, Size:1020Kb

Consumer Chemistry NATIONAL QUALIFICATIONS CURRICULUM SUPPORT Chemistry Consumer Chemistry Predicting Physical Properties of Molecules from Functional Groups [HIGHER] The Scottish Qualifications Authority regularly reviews the arrangements for National Qualifications. Users of all NQ support materials, whether published by Learning and Teaching Scotland or others, are reminded that it is their responsibility to check that the support materials correspond to the requirements of the current arrangements. Acknowledgement Learning and Teaching Scotland gratefully acknowledges this contribution to the National Qualifications support programme for Chemistry. © Learning and Teaching Scotland 2010 This resource may be reproduced in whole or in part for educational purposes by educational establishments in Scotland provided that no profit accrues at any stage. 2 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 Contents Introduction 4 Questions 5 Answers 19 CONSUMER CHEMISTRY (H, CHEMISTRY) 3 © Learning and Teaching Scotland 2010 INTRODUCTION Introduction This resource supports the Consumer Chemistry unit of the revised Higher Chemistry. The resource has the following purposes: 1. to allow students to become familiar with identifying functional groups within everyday molecules, some of which have complex structures 2. to enable students to relate intermolecular forces to the functional groups present 3. to enable students to explain the physical properties of molecules based on the functional groups present. 4 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 QUESTIONS Questions Question 1 Benzaldehyde is an aromatic compound with an almond-like smell, which is used in flavourings and perfumes. Circle and name the functional group on the benzaldehyde molecule below. O C H Benzaldehyde CONSUMER CHEMISTRY (H, CHEMISTRY) 5 © Learning and Teaching Scotland 2010 QUESTIONS Question 2 Cholesterol is an important molecule present in the human body. However, high levels of a certain type of cholesterol in the blood are linked with illnesses such as heart disease and strokes. CH2 CH2 CH3 CH2 CH2 CH 3 CH3 CH3 HO CH C CH C CH CH CH2 CH2 CH2 CH2 CH3 CH2 C CH CH CH2 CH CH CH2 2 Cholesterol (a) Identify the two circled functional groups on the cholesterol molecule . (b) Explain why this compound has a high boiling point. 6 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 QUESTIONS Question 3 β-carotene is a member of a family of chemicals called the carotenoids. It is responsible for the orange colour in many fruits and vegetables, including carrots. CH CH3 3 CH3 CH3 CH2 C CH3 C CH2 CH2 C CH CH C CH CH CH C CH CH CH CH C CH CH CH C CH CH C CH2 CH2 C CH C CH 3 CH3 CH3 2 CH3 -carotene CH3 (a) Which functional group is present throughout the structure of β-carotene? (b) Is the carbon-to-carbon double bond polar or non-polar? (c) Which type of intermolecular forces will exist between β-carotene molecules? CONSUMER CHEMISTRY (H, CHEMISTRY) 7 © Learning and Teaching Scotland 2010 QUESTIONS Question 4 The vanilla bean produces a compound called vanillin, which is used as a flavouring additive in sweet foods such as ice cream. O CH3 H C OH O Vanillin (a) Identify two functional groups present in vanillin. (b) What is the strongest type of intermolecular force present between molecules of vanillin? 8 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 QUESTIONS Question 5 The compounds shown below are active ingredients in over -the-counter drugs. Aspirin is used as an analgesic (to relieve pain) and as an antipyretic (to reduce elevated body temperatures). Ibuprofen is used as an anti - inflammatory agent (to counteract swelling or inflammation of the joints, skin and eyes). O OH C CH CH3 3 O CH3 O C CH C CH3 CH CH2 O OH Aspirin (acetylsalicylic acid) Ibuprofen (a) Which functional group is present in both drug molecules? (b) Which functional group is present in aspirin but not in ibuprofen? CONSUMER CHEMISTRY (H, CHEMISTRY) 9 © Learning and Teaching Scotland 2010 QUESTIONS Question 6 The two compounds shown below have similar molecular mass. CH3 O C C CH H O CH2 CH2 CH HO N C C CH 3 CH2 CH3 Paracetamol Carvone Molecular mass = 151 amu Molecular mass = 150 amu (amu = atomic mass units) (a) Identify two different types of functional group present in paracetamol. (b) Identify two different types of functional group present in carvone. (c) In terms of intermolecular forces, explain why the melting point of paracetamol (168°C) is significantly higher than that of carvone (25°C). 10 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 QUESTIONS Question 7 Capsaicin and zingerone are natural strong-smelling compounds found in chilli pepper and ginger, respectively. O HO CH2 CH2 C CH3 CH3 O Zingerone H CH3 HO CH2 N C CH2 CH2 CH2 CH2 CH CH CH CH3 O CH3 O Capsaicin (a) Identify the two circled functional groups in zingerone. (b) Identify the three circled functional groups in capsaicin. CONSUMER CHEMISTRY (H, CHEMISTRY) 11 © Learning and Teaching Scotland 2010 QUESTIONS Question 8 Oil of wintergreen is an essential oil that is used in aromatherapy massage blends for the joints and muscles. Methyl salicylate is the active ingredient of oil of wintergreen. O C CH3 O OH methyl salicylate (a) Identify the two circled functional groups present in methyl salicylate. (b) Explain whether the hydroxyl group contains a polar or a non-polar bond. 12 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 QUESTIONS Question 9 Lycopene (C40H56) is the red pigment found in tomatoes and other red fruits and vegetables. CH3 CH3 CH3 CH3 H3C C CH CH2 CH2 C CH CH CH C CH CH CH C CH CH CH CH C CH CH CH C CH CH CH C CH2 CH2 CH C CH3 Lycopene CH3 CH3 CH3 CH3 Astaxanthin (C40H52O4) is a pink pigment found in salmon, trout, lobster and shrimp. CH O CH3 3 CH CH C C 3 3 CH3 C CH2 HO CH C CH CH C CH CH CH C CH CH CH CH C CH CH CH C CH CH C CH OH CH2 C CH C C 3 CH3 CH3 CH3 Astaxanthin CH3 O (a) Which functional group is found repeatedly throughout the structure of lycopene? (b) Name two additional functional groups that are found in the structure of astaxanthin. (c) Explain why astaxanthin (215°C) has a higher boiling point than lycopene (172°C). CONSUMER CHEMISTRY (H, CHEMISTRY) 13 © Learning and Teaching Scotland 2010 QUESTIONS Question 10 Tetracycline is an antibiotic that is widely used as an alternative treatment for patients who are allergic to penicillin. It prevents the growth of invading bacteria, allowing the body’s own immune system to fight off infection. CH3 CH3 HO CH3 N C CH2 CH OH CH CH C H C C C N C C C C H OH OH O OH O O Tetracycline Identify four different types of functional group on the tetracycline structure. 14 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 QUESTIONS Question 11 L-tyrosine is an important building block in the formation of almost all proteins in the body. NH2 O HO CH2 CH C OH L-tyrosine Identify three functional groups present in its structure. CONSUMER CHEMISTRY (H, CHEMISTRY) 15 © Learning and Teaching Scotland 2010 QUESTIONS Question 12 Alanine (2-aminopropanoic acid) is found in meat, fish, seafood and dairy products. CH3 H O N CH C H OH alanine Which functional groups are present in an alanine molecule? A. Aldehyde, amine and hydroxyl B. Ketone, amine and hydroxyl C. Carboxyl and amine D. Amino acid and hydroxyl 16 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 QUESTIONS Question 13 Aspirin and ibuprofen are common over-the-counter drugs. O OH C CH CH3 3 O CH3 O C CH C CH3 CH CH2 O OH Aspirin (acetylsalicylic acid) Ibuprofen Identify the term that can be applied to aspirin but not to ibuprofen. A. Aldehyde B. Ketone C. Carboxylic acid D. Ester CONSUMER CHEMISTRY (H, CHEMISTRY) 17 © Learning and Teaching Scotland 2010 QUESTIONS Question 14 Cyclohexyne is used in insect repellents. H H H C H C C H C C C H H H cyclohexyne Which of the following would be the best solvent for dissolving cycloh exyne? A. Hexane B. Hexanal C. Hexanol D. Hexanone 18 CONSUMER CHEMISTRY (H, CHEMISTRY) © Learning and Teaching Scotland 2010 ANSWERS Answers Question 1 Benzaldehyde is an aromatic compound with an almond-like smell, which is used in flavourings and perfumes. Circle and name the functional group on the benzaldehyde molecule below. O Carbonyl group C H Benzaldehyde CONSUMER CHEMISTRY (H, CHEMISTRY) 19 © Learning and Teaching Scotland 2010 ANSWERS Question 2 Cholesterol is an important molecule present in the human body. However, high levels of a certain type of cholesterol in the blood are linked with illnesses such as heart disease and strokes. CH2 CH2 CH3 CH2 CH2 CH 3 CH3 CH3 HO CH C CH C CH CH CH2 CH2 CH2 CH2 CH3 CH2 C CH CH CH2 Hydroxyl group CH CH CH2 2 Carbon-to-carbon double bond Cholesterol (a) Identify the two circled functional groups on the cholesterol molecule Hydroxyl group and carbon-to-carbon double bond. (b) Explain why this compound has a high boiling point. Hydrogen bonding exists between the polar hydroxyl groups on cholesterol molecules. Extra energy is required to overcome these strong intermolecular forces of attraction, and therefore the boiling point is high. Additionally, cholesterol is a large molecule containing a large number of electrons, which leads to relatively strong London forces existing between cholesterol molecules. As more energy is therefore required to separate the molecules, the boiling point is higher.
Recommended publications
  • Fundamental Studies of Early Transition Metal-Ligand Multiple Bonds: Structure, Electronics, and Catalysis
    Fundamental Studies of Early Transition Metal-Ligand Multiple Bonds: Structure, Electronics, and Catalysis Thesis by Ian Albert Tonks In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2012 Defended December 6th 2011 ii 2012 Ian A Tonks All Rights Reserved iii ACKNOWLEDGEMENTS I am extremely fortunate to have been surrounded by enthusiastic, dedicated, and caring mentors, colleagues, and friends throughout my academic career. A Ph.D. thesis is by no means a singular achievement; I wish to extend my wholehearted thanks to everyone who has made this journey possible. First and foremost, I must thank my Ph.D. advisor, Prof. John Bercaw. I think more so than anything else, I respect John for his character, sense of fairness, and integrity. I also benefitted greatly from John’s laissez-faire approach to guiding our research group; I’ve always learned best when left alone to screw things up, although John also has an uncanny ability for sensing when I need direction or for something to work properly on the high-vac line. John also introduced me to hiking and climbing in the Eastern Sierras and Owens Valley, which remain amongst my favorite places on Earth. Thanks for always being willing to go to the Pizza Factory in Lone Pine before and after all the group hikes! While I never worked on any of the BP projects that were spearheaded by our co-PI Dr. Jay Labinger, I must also thank Jay for coming to all of my group meetings, teaching me an incredible amount while I was TAing Ch154, and for always being willing to talk chemistry and answer tough questions.
    [Show full text]
  • The Chemistry of Alkynes
    14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 644 14 14 The Chemistry of Alkynes An alkyne is a hydrocarbon containing a carbon–carbon triple bond; the simplest member of this family is acetylene, H C'C H. The chemistry of the carbon–carbon triple bond is similar in many respects toL that ofL the carbon–carbon double bond; indeed, alkynes and alkenes undergo many of the same addition reactions. Alkynes also have some unique chem- istry, most of it associated with the bond between hydrogen and the triply bonded carbon, the 'C H bond. L 14.1 NOMENCLATURE OF ALKYNES In common nomenclature, simple alkynes are named as derivatives of the parent compound acetylene: H3CCC' H L L methylacetylene H3CCC' CH3 dimethylacetyleneL L CH3CH2 CC' CH3 ethylmethylacetyleneL L Certain compounds are named as derivatives of the propargyl group, HC'C CH2 , in the common system. The propargyl group is the triple-bond analog of the allyl group.L L HC' C CH2 Cl H2CA CH CH2 Cl L L LL propargyl chloride allyl chloride 644 14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 645 14.1 NOMENCLATURE OF ALKYNES 645 We might expect the substitutive nomenclature of alkynes to be much like that of alkenes, and it is. The suffix ane in the name of the corresponding alkane is replaced by the suffix yne, and the triple bond is given the lowest possible number. H3CCC' H CH3CH2CH2CH2 CC' CH3 H3C CH2 C ' CH L L L L L L L propyne 2-heptyne 1-butyne H3C CH C ' C CH3 HC' C CH2 CH2 C' C CH3 L L L L 1,5-heptadiyneLL L "CH3 4-methyl-2-pentyne Substituent groups that contain a triple bond (called alkynyl groups) are named by replac- ing the final e in the name of the corresponding alkyne with the suffix yl.
    [Show full text]
  • Chemical Bonding Valence Electrons Are the Outer Shell Electrons of an Atom
    Chapter 8 Chemical Bonding Valence electrons are the outer shell electrons of an atom. The valence electrons are the electrons that participate in chemical bonding. Group e- configuration # of valence e- 1 ns1 1 2 ns2 2 13 ns2np1 3 14 ns2np2 4 15 ns2np3 5 16 ns2np4 6 17 ns2np5 7 Lewis Dot Symbols for the Representative Elements & Noble Gases Lewis dot symbol consists of the symbol of the element and one dot for each valence electron in an atom of each element The Ionic Bond Ionic bond = the electrostatic force that holds ions Li + F Li+ F - together in an 2 1 2 2 5 [He]2[Ne]2 2 6 ionic compound 1s 2s1s 2s 2p 1s1s 2s 2p Li Li+ + e- e- + F F - Lithium fluoride, LiF Li+ + F - Li+ F - Ionic Bonds 3Mg (s) + N2 (g) → Mg3N2 (s) .. .. 2 3 3 Mg2 N 3Mg 2: N : (Mg3N2 ) . .. Electrostatic (Lattice) Energy Lattice energy (E) is the energy required to completely separate one mole of a solid ionic compound into gaseous ions. Coulomb’s Law: the potential energy between 2 ions is directly proportional to the product of their charges and inversely proportional to the distance of separation between them Q+ is the charge on the cation Q Q E = k + - Q is the charge on the anion r - r is the distance between the ions cmpd lattice energy MgF2 2957 Q= +2,-1 Lattice energy (E) increases MgO 3938 Q= +2,-2 as Q increases and/or as r decreases. LiF 1036 r F- < r Cl- LiCl 853 Born-Haber Cycle for Determining Lattice Energy The Born-Haber cycle relates lattice energies of ionic compounds to ionization energies, electron affinities, and other atomic & molecular properties o o o o o o DHoverall = DH1 + DH2 + DH3 + DH4 + DH5 Born-Haber cycle for lithium fluoride 1.
    [Show full text]
  • Basic Concepts of Chemical Bonding
    Basic Concepts of Chemical Bonding Cover 8.1 to 8.7 EXCEPT 1. Omit Energetics of Ionic Bond Formation Omit Born-Haber Cycle 2. Omit Dipole Moments ELEMENTS & COMPOUNDS • Why do elements react to form compounds ? • What are the forces that hold atoms together in molecules ? and ions in ionic compounds ? Electron configuration predict reactivity Element Electron configurations Mg (12e) 1S 2 2S 2 2P 6 3S 2 Reactive Mg 2+ (10e) [Ne] Stable Cl(17e) 1S 2 2S 2 2P 6 3S 2 3P 5 Reactive Cl - (18e) [Ar] Stable CHEMICAL BONDSBONDS attractive force holding atoms together Single Bond : involves an electron pair e.g. H 2 Double Bond : involves two electron pairs e.g. O 2 Triple Bond : involves three electron pairs e.g. N 2 TYPES OF CHEMICAL BONDSBONDS Ionic Polar Covalent Two Extremes Covalent The Two Extremes IONIC BOND results from the transfer of electrons from a metal to a nonmetal. COVALENT BOND results from the sharing of electrons between the atoms. Usually found between nonmetals. The POLAR COVALENT bond is In-between • the IONIC BOND [ transfer of electrons ] and • the COVALENT BOND [ shared electrons] The pair of electrons in a polar covalent bond are not shared equally . DISCRIPTION OF ELECTRONS 1. How Many Electrons ? 2. Electron Configuration 3. Orbital Diagram 4. Quantum Numbers 5. LEWISLEWIS SYMBOLSSYMBOLS LEWISLEWIS SYMBOLSSYMBOLS 1. Electrons are represented as DOTS 2. Only VALENCE electrons are used Atomic Hydrogen is H • Atomic Lithium is Li • Atomic Sodium is Na • All of Group 1 has only one dot The Octet Rule Atoms gain, lose, or share electrons until they are surrounded by 8 valence electrons (s2 p6 ) All noble gases [EXCEPT HE] have s2 p6 configuration.
    [Show full text]
  • Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc
    Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc Richard H. Duncan Lyngdoh*,a, Henry F. Schaefer III*,b and R. Bruce King*,b a Department of Chemistry, North-Eastern Hill University, Shillong 793022, India B Centre for Computational Quantum Chemistry, University of Georgia, Athens GA 30602 ABSTRACT: This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) n+ the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) , (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging.
    [Show full text]
  • Alkenes and Alkynes
    02/21/2019 CHAPTER FOUR Alkenes and Alkynes H N O I Cl C O C O Cl F3C C Cl C Cl Efavirenz Haloprogin (antiviral, AIDS therapeutic) (antifungal, antiseptic) Chapter 4 Table of Content * Unsaturated Hydrocarbons * Introduction and hybridization * Alkenes and Alkynes * Benzene and Phenyl groups * Structure of Alkenes, cis‐trans Isomerism * Nomenclature of Alkenes and Alkynes * Configuration cis/trans, and cis/trans Isomerism * Configuration E/Z * Physical Properties of Hydrocarbons * Acid‐Base Reactions of Hydrocarbons * pka and Hybridizations 1 02/21/2019 Unsaturated Hydrocarbons • Unsaturated Hydrocarbon: A hydrocarbon that contains one or more carbon‐carbon double or triple bonds or benzene‐like rings. – Alkene: contains a carbon‐carbon double bond and has the general formula CnH2n. – Alkyne: contains a carbon‐carbon triple bond and has the general formula CnH2n‐2. Introduction Alkenes ● Hydrocarbons containing C=C ● Old name: olefins • Steroids • Hormones • Biochemical regulators 2 02/21/2019 • Alkynes – Hydrocarbons containing C≡C – Common name: acetylenes Unsaturated Hydrocarbons • Arene: benzene and its derivatives (Ch 9) 3 02/21/2019 Benzene and Phenyl Groups • We do not study benzene and its derivatives until Chapter 9. – However, we show structural formulas of compounds containing a phenyl group before that time. – The phenyl group is not reactive under any of the conditions we describe in chapters 5‐8. Structure of Alkenes • The two carbon atoms of a double bond and the four atoms bonded to them lie in a plane, with bond angles of approximately 120°. 4 02/21/2019 Structure of Alkenes • Figure 4.1 According to the orbital overlap model, a double bond consists of one bond formed by overlap of sp2 hybrid orbitals and one bond formed by overlap of parallel 2p orbitals.
    [Show full text]
  • Representation of Three-Center−Two-Electron Bonds in Covalent Molecules with Bridging Hydrogen Atoms Gerard Parkin*
    Article Cite This: J. Chem. Educ. 2019, 96, 2467−2475 pubs.acs.org/jchemeduc Representation of Three-Center−Two-Electron Bonds in Covalent Molecules with Bridging Hydrogen Atoms Gerard Parkin* Department of Chemistry, Columbia University, New York, New York 10027, United States *S Supporting Information ABSTRACT: Many compounds can be represented well in terms of the two-center−two-electron (2c−2e) bond model. However, it is well-known that this approach has limitations; for example, certain compounds require the use of three- center−two-electron (3c−2e) bonds to provide an adequate description of the bonding. Although a classic example of a compound that features a 3c−2e bond is provided by − fi diborane, B2H6,3c 2e interactions also feature prominently in transition metal chemistry, as exempli ed by bridging hydride compounds, agostic compounds, dihydrogen complexes, and hydrocarbon and silane σ-complexes. In addition to being able to identify the different types of bonds (2c−2e and 3c−2e) present in a molecule, it is essential to be able to utilize these models to evaluate the chemical reasonableness of a molecule by applying the octet and 18-electron rules; however, to do so requires determination of the electron counts of atoms in molecules. Although this is easily achieved for molecules that possess only 2c− 2e bonds, the situation is more complex for those that possess 3c−2e bonds. Therefore, this article describes a convenient approach for representing 3c−2e interactions in a manner that facilitates the electron counting procedure for such compounds. In particular, specific attention is devoted to the use of the half-arrow formalism to represent 3c−2e interactions in compounds with bridging hydrogen atoms.
    [Show full text]
  • Bsc Chemistry
    Subject Chemistry Paper No and Title Paper 1: ORGANIC CHEMISTRY- I (Nature of Bonding and Stereochemistry) Module No and Module 3: Hyper-Conjugation Title Module Tag CHE_P1_M3 CHEMISTRY PAPER No. 1: ORGANIC CHEMISTRY- I (Nature of Bonding and Stereochemistry) Module No. 3: Hyper-Conjugation TABLE OF CONTENT 1. Learning outcomes 2. Introduction 3. Hyperconjugation 4. Requirements for Hyperconjugation 5. Consequences and Applications of Hyperconjugation 6. Reverse Hyperconjugation 7. Summary CHEMISTRY PAPER No. 1: ORGANIC CHEMISTRY- I (Nature of Bonding and Stereochemistry) Module No. 3: Hyper-Conjugation 1. Learning Outcomes After studying this module you shall be able to: Understand the concept of hyperconjugation. Know about the structural requirements in a molecule to show hyperconjugation. Learn about the important consequences and applications of hyperconjugation. Comprehend the concept of reverse hyperconjugation. 2. Introduction In conjugation, we have studied that the electrons move from one p orbital to other which are aligned in parallel planes. Is it possible for electron to jump from p orbital to sp3 orbital that are not parallelly aligned with one another? The answer is yes. This type of conjugation is not normal, it is extra-ordinary. Hence, the name hyper-conjugation. It is also know as no-bond resonance. Let us study more about it. 3. Hyperconjugation The normal electron releasing inductive effect (+I effect) of alkyl groups is in the following order: But it was observed by Baker and Nathan that in conjugated system, the attachment of alkyl groups reverse their capability of electron releasing. They suggested that alkyl groups are capable of releasing electrons by some process other than inductive.
    [Show full text]
  • Chemical Bonding Chemical Bonding Chemical Bonding
    Chemical Bonding • Petrucci, Harwood and Herring: Chapters 10 and 11 • Aims: – To look at bonding and possible shapes of molecules • We will mainly do this through Lewis structures – To look at ionic and covalent bonds – Use valence shell electronic structure to predict shapes of molecules CHEM 1000 3.0 Chemical Bonding I 1 Chemical Bonding • The most important concepts here are: – Electrons, particularly valence electrons play a fundamental role in chemical bonding. – When elements combine to produce compounds they are attempting to achieve a valence shell like a noble gas CHEM 1000 3.0 Chemical Bonding I 2 Chemical Bonding • The driving force for the production of chemical bonds is the need for an atom to complete a valence shell (usually 8 electrons) – Often electrons can be transferred from one atom to another to make ions. The atoms are then held together by coulombic forces in an ionic bond – More often the only way an atom can gain electrons is by sharing. This sharing produces a covalent bond CHEM 1000 3.0 Chemical Bonding I 3 •1 Lewis Symbols • This is a way of representing the valence electrons in an element – It does not include the inner shell electrons – It does not include the spin of an electron – e.g. Si ([Ne]3s 23p 2) Si – N ([He]2s 22p 3) N CHEM 1000 3.0 Chemical Bonding I 4 Lewis Structures • These are the combination of Lewis symbols that represents the sharing or transfer of electrons in a molecule – Examples – Ionic bond Na x + Cl [Na] + [ x Cl ] - – Covalent bond Hx + Cl H x Cl CHEM 1000 3.0 Chemical Bonding I 5 Ionic Compounds • We don’t usually see isolated ionic compounds – Normally they are in crystals where one anion (negative) is attached to several cations (positive) and vice versa.
    [Show full text]
  • Conjugated Molecules
    Conjugated Molecules - Conjugated molecules have alternating single and multiple (i.e. double or triple) bonds. Example 1: Nomenclature: 2,6-dimethylhepta-2,5-diene This molecule is not conjugated because it does not have alternating single and multiple bonds (the arrangement of the bonds starting from C2 is double, single, single and double). Between the two double bonds, there is a saturated center (C4) and two intersecting single bonds. Example 2: Nomenclature: 2,5-dimethylhexa-2,4-diene This molecule is conjugated because the arrangement of the bonds starting at C2 is double, single, and double. They are alternated. Example 3: Nomenclature: (2E)-hept-2-en-5-yne note: (2E) is a stereochemical identifier. The letter “E” indicates the arrangement of the double bond (where E usually refers to trans and Z refers to cis). The number “2” indicates the position of the double bond. This molecule is not conjugated because the single and multiple bonds are not alternated. Example 4: Nomenclature: (2Z)-hex-2-en-4-yne This molecule is conjugated because there is an alternation of multiple and single bonds (double, single, and triple starting from C2). More examples: note: the term conjugation refers to parts of the molecule. If you can find one conjugated system within the molecule, that molecule is said to be conjugated. Example: In this molecule, the double bond A is not conjugated. However, since double bond B is conjugated with double bond C, the molecule is said to be conjugated. Special Nomenclature: The Letter "S" stands for “single” and indicates that we are talking about the conjugated double bonds.
    [Show full text]
  • II. Nomenclature Rules for Alkenes 1. the Parent Name Will Be the Longest
    1 Lecture 9 II. Nomenclature Rules For Alkenes 1. The parent name will be the longest carbon chain that contains both carbons of the double bond. Drop the -ane suffix of the alkane name and add the –ene suffix. Never name the double bond as a prefix. If a double bond is present, you have an alkene, not an alkane. alkane + -ene = alkene 2. Begin numbering the chain at the end nearest the double bond. Always number through the double bond and identify its position in the longest chain with the lower number. In the older IUPAC rules the number for the double bond was placed in front of the stem name with a hyphen. Under the newer rules, the number for the double bond is placed right in front of “ene”, with hyphens. We will use the newer rules for specifying the location of pi bonds. 1 2 3456 H3CCHCH CH 2 CH2 CH3 hex-2-ene (newer rules) 2-hexene (older rules) 3. Indicate the position of any substituent group by the number of the carbon atom in the parent (longest) chain to which it is attached. CH 1 2 345 3 H3CCHCHCHCH2 CH CH3 6 7 CH3 Numbering is determined by the double bond, not the branches, because the double bond has 5,6-dimethylhept-3-ene (newer rules) higher priority than any alkyl branch. 5,6-dimethyl-3-heptene (older rules) 4. Number cycloalkenes so that the double bond is 1,2 (number through the double bond). Number in the direction about the ring so that the lowest number is used at the first point of difference.
    [Show full text]
  • Are Carbonahalogen Double and Triple Bonds Possible? Robert Kalescky, Elfi Kraka, and Dieter Cremer*
    FULL PAPER WWW.Q-CHEM.ORG Are CarbonAHalogen Double and Triple Bonds Possible? Robert Kalescky, Elfi Kraka, and Dieter Cremer* The carbonAhalogen and carbonAchalcogen bonding of 84 responding F-derivatives. Diatomic CF1 and CCl1 possess fully molecules was investigated utilizing local vibrational modes developed double bonds but not, as suggested in the litera- calculated at the M06-2X/cc-pVTZ level of theory including ture, triple bonds. Halonium ions have fractional (electron-defi- anharmonicity corrections in all cases. The relative bond cient) CX bonds, which can be stabilized by r-donor strength order of each CX or CE bond (X 5 F, Cl; E 5 O, S) was substituents or by an increased polarizability of the halogen derived from the local CX or CE stretching force constant and atom as with Cl. Bridged halonium ions are more stable than compared with trends of calculated bond lengths r and bond their acyclic counterparts, which results from more effective dissociation energies (BDE) obtained at the G3 level of theory. two-electron-three-center bonding. VC 2014 Wiley Periodicals, It is shown that both bond length r and BDE are not reliable Inc. bond strength descriptors. The CX double bond is realized for some Cl-substituted carbenium ions, however, not for the cor- DOI: 10.1002/qua.24626 Introduction To determine bond strength, we use a dynamic property of the bond. By moving the atoms out of their equilibrium posi- Halogens such as fluorine or chlorine are known to establish tion, a restoring force proportional to the bond strength can [1] single bonds with C in line with their monovalent character.
    [Show full text]