ORCHMD1:LEC
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| 🇬🇧 | 🇬🇧 |
| Compounds: Benzene and all substances with structures and chemical properties that resemble benzene | Aromatic compounds |
| First isolated Benzene (the parent substance of the aromatic hydrocarbons) | Michael Faraday (1825) |
| Proposed that the carbon atoms in a benzene molecule are arranged in a six-membered ring | August Kekulé (1865) |
| August Kekulé model of the benzene molecule is described as: | One hydrogen atom bonded to each carbon atom & three carbon–carbon double bonds |
| Suggested that the double bonds are in rapid oscillation within the molecule. | August Kekulé (1865) |
| Soon realized that there should be two dibromobenzenes, based on double and single-bond positions relative to the two bromine atoms | August Kekulé (1865) |
| Made a landmark in the history of chemistry. | August Kekulé (1865) |
| His was the basis of the best representation of the benzene molecule devised in the nineteenth century | August Kekulé (1865) |
| Kekulé's model's shortcoming | They represent benzene and related substances as highly unsaturated compounds but benzene does not react like a typical alkene |
| Tests that explain how kekule's theory represents benzene and related substances as highly unsaturated compounds but benzene does not react like a typical alkene | The benzene does not decolorize bromine solutions rapidly & it does not destroy the purple color of permanganate ions (Baeyer test). |
| How does benzene behave | Benzene behaves chemically like a typical alkane: Its reactions are usually of the substitution type |
| Permitted chemists to determine the actual distances between the nuclei of carbon atoms in molecules. | X-ray diffraction |
| Kekule's problem was not resolved until this development | X-ray diffraction |
| Explain why benzene does not readily undergo addition or elimination reactions but does undergo substitution reactions. | Its electronic structure is stable from the electrons not being attached to particular carbon atoms but are delocalized and associated with the entire molecule |
| Whose model/theory? | Kekulé |
| Elaborate the shortcomings of this structure | Although in some circumstances they are still used, neither structures actually exists |
| What is this structure/formula? what does it represent? | Representation of the real benzene molecule (hybrid structure) ○ The circle indicates the special nature of the benzene pi bonds. ○ the hexagon with the circle to represent a benzene ring. |
| Substances in which one or more hydrogen atoms in the ring have been replaced by other atoms or groups. | Benzene derivatives |
| Most common benzene derivatives | Substituted benzenes |
| Derived by replacing one or more hydrogen atoms of benzene by another atom or group of atoms. | Substituted benzenes |
| Are named by adding the name of the substituent group as a prefix to the word benzene. | Monosubstituted benzene |
| What does the G from C6H5G represent | G is the group replacing a hydrogen atom |
| The position of the substituent is not important here since they are all equivalent | Monosubstituted benzene |
| Give the name of this benzene derivative | Benzoic acid |
| Give the name of this benzene derivative | Benzaldehyde |
| C6H5 group | Phenyl group |
| Two substituent groups replace two hydrogen atoms in a benzene molecule | Disubstituted Benzenes |
| Used to name disubstituted benzenes. | The prefixes ortho-, meta-, and para- |
| The two substituents are located on adjacent carbon atoms of the benzene ring | Ortho disubstituted compounds (1,2) |
| The two substituents are one carbon apart | Meta disubstituted compounds (1,3) |
| The two substituents are located on opposite points of the hexagon | Para disubstituted compounds (1,4) |
| When there are more than two substituents on a benzene ring | Polysubstituted Benzenes |
| Another name for polycyclic aromatic compounds | Fused aromatic ring system |
| Their structures consist of two or more rings in which two carbon atoms are common to two rings. | Polycyclic aromatic compounds |
| Three of the most common polycyclic aromatic compounds | Naphthalene, anthracene, & phenanthrene. |
| One hydrogen is attached to each carbon atom, except ____________ | At the carbons common to two rings. |
| Identify this polycyclic aromatic compound | Naphthalene |
| Identify this polycyclic aromatic compound | Phenanthrene |
| A number of the polycyclic aromatic hydrocarbons (and benzene) have been shown to be _______________ | Carcinogenic |
| 2 sources of aromatic hydrocarbons | Coal & petroleum |
| Products of heating coal at high temperatures in the absence of air | Coke (C), coal gas and coal tar |
| Physical characteristics of coke | Grayish black color, hard and porous solid |
| Uses of coke | Used as fuels for stoves, furnaces and blacksmithing |
| Obtained from the production of coke characterized by its unpleasant and is a highly flammable gas | Coal gas |
| Main component of coal gas | Methane |
| What was the early use of coal gas | Source of light |
| What is the modern use of coal gas | Domestic and industrial purposes |
| Physical characteristics of coal tar | Grayish black color, Highly viscous liquid, Unpleasant smell |
| By-products of the manufacture of coke | Coal gas & coal tar |
| Phases of aromatic hydrocarbons | May be liquid or solid |
| Density of aromatic hydrocarbons | Less dense than water |
| Most characteristic reactions of aromatic hydrocarbons | Substitution reaction |
| Does not change the number of atoms bonded to each carbon. | Substitution reaction |
| Net addition of -Br/-Cl | Halogenation |
| Catalysts of halogenation of aromatic hydrocarbons | Iron(III) chloride or iron(III) bromide |
| Halogenated aromatic hydrocarbons blue litmus paper test result | Will turn the litmus paper red |
| Net addition of -NO2 | Nitration |
| Catalyst of the nitration of aromatic hydrocarbons | Concentrated sulfuric acid |
| Net addition of -R (Alkyl group) | Alkylation |
| Another name for Alkylation | Friedel–Craft reaction |
| Catalyst of the alkylation of aromatic hydrocarbons | Aluminum chloride |
| Early syntheses were developed by ____________ methods. | Trial-and-error |
| The mechanisms following aromatic substitution reactions | Electrophilic substitution |
| For this oxidation to occur, there must be at least one hydrogen atom on the carbon bonded to the aromatic ring | Side chain oxidation |
| Reagents commonly used for oxidation in the laboratory are | Potassium permanganate, potassium dichromate & Sulfuric acid |