Benzene and its Derivatives PDF

MODULE 3 BENZENE AND ITS DERIVATIVES …………………………………………………………………………………………………………………. I. INTRODUCTION This module will explain the rules in naming aromatic compounds that has a single substituents, two substituents and three or more substituents. Furthermore, this module also explains the characteristic...

MODULE 3 BENZENE AND ITS DERIVATIVES …………………………………………………………………………………………………………………. I. INTRODUCTION This module will explain the rules in naming aromatic compounds that has a single substituents, two substituents and three or more substituents. Furthermore, this module also explains the characteristic reactions of benzene and its derivatives particularly about aromatic substitution. The author believes that your learnings on the previous modules about hydrocarbons specifically alkanes, alkenes and alkynes had prepared you enough to engage in challenging lessons as you explore and learn more about organic chemistry. In this module, you will learn more about benzene and its derivatives. II. MODULE CONTENTS: This module is divided into lesson 1 and lesson 2; Lesson 1 is about Naming Aromatic Compounds; Lesson 2 is about Characteristics of Benzene and its Derivatives. III MODULE LEARNING OUTCOMES In this module, you are expected to: 1. state the rules in naming Aromatic compounds; 2. differentiate Kekule’s Struture of Benzene and Resonance structure of benzene; 3. name and draw aromatic compounds with one or more substituents; 4. explain the differences between the characteristic reaction of Benzene and its derivatives; and 5. relate the importance of Benzene and its derivatives in your College of Criminal Justice Education. IV PRE-ASSESSMENT Direction: Read each question carefully. Choose the letter of the best answer, and write the letter of your choice on the space provided for each number 1. Which of the following has a molecular structure of C 6H6? a. alkanes b. alkenes c. alkynes d. benzene 2. Who developed the resonance structure of benzene? a. Friedrich Kekule b. Linus Pauling c. Isaac Newton d. James Chadwick 3. What is the term used to described the individual Lewis structure in the resonance structure of benzene? a. Resonance Hybrid b. Contributing structure c. Kekule Structure d. Resonance Lewis structure 4. Which of the following locators indicates a consecutive placement of substituents as represented by 1,2- ? a. meta b. ortho c. para d. giga 5. Halogenation occurs when a halogen reacts with benzene. Which of the following is a halogen? a. Iron b. Neon c. Chlorine d. Hydrogen 6. What element allows halogens to react rapidly with benzene? a. Iron b. Neon c. Chlorine d. Hydrogen 7. What characteristic reactions of benzene occurs when a nitro (-NO2) group replaces one of the hydrogen atoms bonded to the ring? a. Halogenation b. Nitration c. Sulfonation d. Acidity 8. Which of the following locators indicates a opposite placement of substituents as represented by 1,4in benzene? a. Meta b. Ortho c. Para d. phenyl 9. Which of the following is not a halogen? a. Fluorine b. Chlorine c. Barium d. Bromine 10. Which of the following locators is represented by 1,4- in benzene? a. Ortho b. Meta c. Para d. substituent V LESSON MAP Aromatic Compounds Benzene and its derivatives Characteristic Reactions of Benzene and its derivatives Structure of Benzene and its derivatives Naming Benzene and its derivatives Kekule’s Structure Halogenation IUPAC System Resonance Structure Nitration Sulfonation The map describes the content of the module 4. This module will discuss the structure of Benzene as well as naming using the IUPAC system and the characteristic reactions of Benzene and its derivatives VI a. CORE CONTENT ENGAGE: LIGHTING A SPARK! Activity 1: READING ACTIVITY Instruction. Read the selection below and answer the questions that follow. Benzene and two of its derivatives Benzene and Worker Cancers: “An American Tragedy” Bloated and bed-ridden, his skin browned by blood transfusions, John Thompson succumbed to leukemia on November 11, 2009. A carpenter by trade, Thompson, then 70, had spent much of his life building infrastructure for the petrochemical industry in his native Texas — synthetic rubber plants in Port Neches, chemical facilities in Orange. Throughout the 1960s and early 1970s, he often encountered benzene, stored on job sites in 55-gallon drums, which he used as a cleaning solvent. He dipped hammers and cutters into buckets full of the sweetsmelling liquid; to expunge tar, he soaked gloves and boots in it. Thompson never figured the chemical could do him harm. Not when it stung his hands or turned his skin chalky white. Not even when it made him faint. But after being diagnosed with a rare form of leukemia in 2006, relatives say, he came to believe his exposure to benzene had amounted to a death sentence. Oil and chemical companies knew about the hazard, Thompson felt, but said nothing to him and countless other workers. Thompson died before a lawsuit filed by his family against benzene suppliers could play out in court, where science linking the chemical to cancer could be put on display. Over the past 10 years, however, scores of other lawsuits, most filed by sick and dying workers like Thompson, have uncovered tens of thousands of pages of previously secret documents detailing the petrochemical industry’s campaign to undercut that science. Although there limitations implemented by the government to reduce and control exposure to harmful Benzene compounds, a 2004 National Cancer Institute suggested there’s no safe threshold for people working with the chemical. Source:https://publicintegrity.org/environment/benzene-and-worker-cancers-an-american-tragedy/ Process Questions: 1. What do you think should be done to limit the workers’ exposure to Benzene? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ _____________________________________________________________________________ 2. Cite a similar case in the Philippines, wherein Benzene or other harmful chemicals were involved in the demise or had cause an injury to an individual. ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ _____________________________________________________________________________ 3. As a future law enforcer, what laws do you think should be implemented to limit exposure of factory workers to harmful chemicals aside from Benzene? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ _____________________________________________________________________________ 4. Why is it important to study Benzene and its derivatives? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ _____________________________________________________________________________ b. EXPLORE: DISCOVERING BENZENE AND ITS DERIVATIVES Activity 2: Reading and Analysing Activity Instruction: Carefully read the texts below. The information you gather here will be used in the latter sections of this lesson. A. What is the Structure of Benzene? Benzene, the simplest aromatic hydrocarbon, was discovered by Michael Faraday in 1825. Its structure presented an immediate problem to chemists of the day. Benzene has a molecular formula of C6H6, and a compound with so few hydrogen or its six carbons, chemists argued, should be unsaturated. But Benzene does not behave like an alkene (the only class of unsaturated hydrocarbons known at that time). Whereas 1-hexene, for example, reacts instantly with BR2, benzene does not react at all with this reagent. Nor does benzene react with HBr, H2O/H2SO4,or H2/Pd – all reagents that normally add to carboncarbon double bonds. Kekule’s Structure of Benzene The first structure for benzene was proposed by Friedrich August Kekule in 1872 and consisted o a six-membered ring with alternating single and double bonds, with one hydrogen bonded to each carbon. Although Kekule’s proposal was consistent with many of the chemical properties of benzene, it was contested or years. The major objection was its failure to account for the unusual behaviour of benzene. If benzene contains double three bonds, Kekule’s critics asked,why doesn’t it undergo reactions typical of alkenes? Resonance Structure of Benzene The concept of resonance, developed by Linus Pauling in the 1930s, provided the first adequate description of the structure of benzene. According to the theory of resonance, certain molecules and ions are best described by writing two or more Lewis structures and considering the real molecule or ion to be a resonance hybrid of these structures. Each individual Lewis structure is called a contributing structure. To show that the real molecule is a resonance hybrid of two Lewis structures, we position a double headed arrow between them. Alternating Lewis contributing structures for benzene B. HOW DO WE NAME AROMATIC COMPOUNDS? a) One Substituent Monosubstituted alkylbenzenes are named as derivatives of benzene – for example, ethylbenzene. The IUPAC system retains certain common names for several of the simpler monosubstituted alkylbenzenes, including toluene and tyrene. The IUPAC system also retains common names for the following compounds; b) Two Substituent When two substituents occur on a benzene ring, three isomers are possible. We locate the substituteens either by numbering the atoms of the ring or by using the locators ortho (o), meta (m), and para (p). The numbers are 1,2- are equivalent to ortho; 1,3- to meta; and 1,4- for para. When one of the two substituents on the ring imparts a special name to the compound (for example, CH3, -OH, -NH2, or -COOH), we name the compound as a derivative of that parent molecule and assume that the substitutuent occupies ring position number 1. The IUPAC system retains the common name xylene for the three Isomeric dimethylbenzenes. Where niether substituent imparts a special name, we locate the two substituents and list them in the alphabetical order before ending the “benzene”. The carbon of the Benzene ring with the substituent of lower alphabetical ranking is numbered C-1. C) Three or More Subtituents When three or more subtituents are present on a benzene ring, specify their location by numbers. If one of the substituents imparts a special name, then name the molecule as a derivative of parent molecule. If none of the substituents imparts a special name, then locate the substituents, number them to give the smallest set of numbers, and list them in alphabetical order, before the ending “benzene”. In the following examples, the first compound derivative of toluene and the second is a derivative of phenol. Because no substituent in the third compound imparts a special name, list its three substituents in alphabetical order followed by the word “benzene”. C. WHAT ARE THE CHARACTERISTIC REACTIONS OF BENZENE AND ITS DERIVATIVES? The most charactristics reaction of aromatic compounds is substitution at a ring carbon, which we give the name aromatic substitution. A. Halogenation Halogens are the elements that belong to group VIIa of the periodic table. The halogen elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). Chlorine (Cl) and Bromine (Br) do note react with benzene under normal circumstances, but when the presence of iron is used as a catalyst, both halogens react rapidly with benzene. Halogenation occurs when a halogen reacts with benzene. B. Nitration When we heat benzene or one of its derivatives with a mixture of concentrated nitric and sulfuric acids, a nitro (-NO2) group replaces one of the hydrogen atoms bonded to the ring. C. Sulfonation Heating an aromatic compound with concentrated sulfuric acid results in formation of an arenesulfuric acid, all of which are strong acids, comparable in strength to sulfuric acids. c. EXPLAIN Activity 3: CRITICAL THINKING Instruction: Answer the questions below. 1. How does the presence of Iron affects Halogenation? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2. How does the following occur? a) Halogenation ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ b) Sulfonation ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ c) Nitration ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ Activity 4: Chemical Connections Instruction: Read the selection below and answer the questions that follow. The Nitro Group in Explosives Treatment of toluene with 3 moles of nitric acid in the presence of sulfuric acid as catalyst results in nitration of toluene three times to form the explosives 2,4,6-trinitoluene, TNT. The presence of these three nitro groups confers explosive properties to TNT. Similarly, the presence of three nitro groups leads to the explosive properties of nitroglycerin. In recent years, several new explosives have been discovered, all of which contain multiple nitro groups. Among then are RDX and PETN. It was used in the destruction of Pan Am flight 103 over Lockerbie, Scotland, in December 1988. PROCESS QUESTIONS: 1. Toluene is one of the derivatives of benzene frequently used in creating explosives. Can you identify atleast 2 other derivatives of benzene used in similar areas? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2. Based on the selection above, what characteristic reaction of benzene is used in the process of creating explosives? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 3. Can you identify similar cases in the Philippines, wherein a benzene or its derivatives is used as a component in using explosives? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 4. What measures does the government implement to prevent terror attacks from homemade explosives? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 5. Does the Philippine government implement laws against terror attacks such as the destruction of Pan Am flight 103? State the law and elaborate. ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ VIII TOPIC SUMMARY In this lesson, you learned that: Benzene, the simplest aromatic hydrocarbon, was discovered by Michael Faraday in 1825. The first structure for benzene was proposed by Friedrich August Kekule in 1872 and consisted o a six-membered ring with alternating single and double bonds, with one hydrogen bonded to each carbon. The concept of resonance, developed by Linus Pauling in the 1930s, provided the first adequate description of the structure of benzene. According to the theory of resonance, certain molecules and ions are best described by writing two or more Lewis structures and considering the real molecule or ion to be a resonance hydrid of these structures. The IUPAC system retains certain common names for several of the simpler monosubstituted alkylbenzenes, including toluene and tyrene. When two substituents occur on a benzene ring, three isomers are possible. We locate the substituteens either by numbering the atoms of the ring or by using the locators ortho (o), meta (m), and para (p). The numbers are 1,2- are equivalent to ortho; 1,3- to meta; and 1,4- for para. Halogenation occurs when a halogen reacts with benzene. Nitration occurs when a nitro (-NO2) group replaces one of the hydrogen atoms bonded to the ring. Heating an aromatic compound with concentrated sulfuric acid results in formation of an arenesulfuric acid, all of which are strong acids, comparable in strength to sulfuric acids. REFERENCES Books: Bettelheim, F.A., Brown. W.H., Campbell, M.K., Farrell, S.O., Torres, O.J. (10th edition). Introduction to General, Organic and Biochemistry. @2014 Cengage Learning Asia Pte Ltd., 1st Philippine reprint 2014 Padolina, Ma. Christina D., Simon-Antero, E., Alumaga, Ma. J.B., Estanilla, L.C., Rabago, L.M. (2004). Conceptual and Functional Chemistry, Modular Approach. Vibal Publishing House, Inc. Websites: Anon, (2020). Structures and Names of Alkanes. (2020, September 27). Retrieved March 20, 2021, from https://chem.libretexts.org/@go/page/16064