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Organic Chemistry : Ch. 9 Organic chemistry is the branch of chemistry which deals with “carbon based” compounds. Carbon is an element which has the unique ability to bond long chains, rings, and react with other elements to form a variety of compounds. Carbon Compounds Carbon compounds are found in many forms : gases, aqueous, and solids. Carbon is recycled in nature by the carbon cycle. Carbon chains can be modified by reactions to form different type of carbon based (organic) compounds. Story of Carbon Carbon is a major component of living things. Lipids (fats and oils), sugars, starches, proteins, DNA, etc. are composed of carbon, hydrogen, oxygen, nitrogen, and other atoms. Lipids, sugars, and starches are composed of carbon, hydrogen, and oxygen. Proteins are composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Story of Carbon Some carbon compounds are not considered organic. Eg Oxides of carbon (CO2 , CO ) Ionic compounds of carbon like carbonate, cyanide ions and carbides where carbon behaves like a negative ion. Not organic Sodium carbonate, hydrogen cyanide, calcium carbide Story of Carbon When the oxygen, nitrogen, sulfur, and other atoms are removed by bacteria, what is left is a hydrocarbon ( Carbon and hydrogen only) These hydrocarbons are of mixed sizes, and are known as “crude oil” when recovered from the earth. Hydrocarbons : C & H atoms Story of Carbon Carbon atoms have four electrons in their outer energy level, and will want to covalently bond (share electrons) with itself and other atoms to form more stable chain and ring compounds. The crude oil contains a mixture of hydrocarbons including : butane(lighter fluid), gasoline, diesel, candle wax, etc. Story of Carbon The hydrocarbons found in crude oil can be separated based upon their boiling points and refined or distilled. By adding substances to them a host of other organic compounds can be produced : (alcohols, esters, ethers, plastic, styrofoam, etc.) Hydrocarbons Hydrocarbons are a class of organic compounds which contain only carbon and hydrogen. Hydrocarbons are characterized as carbon chains, branched chains, and rings. Fossil Fuels are primary sources of hydrocarbons. These include Natural Gas, Crude Oil, Heavy Oil, Oil Sands, and Coal. Refining is the process that separates and purifies the mixtures Hydrocarbons Carbon has 4 valence electrons and will form 4 covalent bonds with hydrogen. A line between carbon and another atom represents the sharing of 2 electrons. Therefore every carbon in an organic compound needs 4 lines around it. Hydrocarbons with all single carbon bonds are described as the Alkanes. http://www.nyu.edu/pages/mathmol/library/hydrocarbons/ Families of Organic Compounds Organic compounds can be grouped into families by their common structural features We shall survey the nature of the compounds in a tour of the families in this unit. This basic family or series for hydrocarbons are the alkanes, compounds that contain only carbons and hydrogens, all connected exclusively by single bonds The chains of carbons can be rearranged to form different shapes with the same number and kinds of atoms. These are called isomers. Alkanes and Alkane Isomers Alkanes: Compounds with C-C single bonds and C-H bonds only (no functional groups) Connecting carbons can lead to large or small molecules The formula for an alkane with no rings in it must be CnH2n+2 where the number of C’s is n Alkanes are saturated with hydrogen (no more can be added They are also called aliphatic compounds Naming Alkanes Basic principles The name for an alkane is based on Greek root with the suffix –ane. Alkanes Branched Hydrocarbons Hydrocarbons come in a variety of forms. Not all hydrocarbons are linear, some are branched and some are cyclic. Branched hydrocarbons have a carbon “backbone” with “groups” attached to this backbone. To name these compounds you need to follow the basic rules below: (IUPAC) Find the longest carbon chain (backbone) and write its corresponding name. Identify the groups attached to this chain. Assign the carbons in the chain numbers, which make the “group” have the lowest number. Identify any double or triple bonds with the corresponding carbon number. Branched Hydrocarbons Branched hydrocarbons are found in crude oil and can also by synthesized by chemical reactions. Hydrocarbons with only single bonds are termed “saturated” hydrocarbons. Hydrocarbons with a double or triple bond are called “unsaturated” Saturated hydrocarbon : Pentane hydrocarbons. Naming Alkanes Basic principles For branched hydrocarbons use the longest continuous chain for the root name. Naming Alkanes Basic principles Alkanes missing one H atom can have another hydrocarbon attached at the missing H point. Naming Alkanes Basic principles Specify the names of groups by numbering the C atoms starting at the end closest to the branching. Naming Alkanes Basic principles Additional groups attached to the main chain are called branches and here are the most common alkyl or hydrocarbon groups. Naming Alkanes Basic principles If a group occurs more than once use a prefix to show this. The numbers show the carbon where the group is attached. Use commas and dashes. Eg. 2,3-dimethylpentane Naming Alkanes Practice Diagram the following branched hydrocarbons: a) 2 methyl, hexane b) 2,2, dimethyl pentane c) 2,3 dimethyl octane d) 2,4 dimethyl 3-decene Cycloalkanes Cycloalkanes are alkanes that have carbon atoms that form a ring (called alicyclic compounds) Simple cycloalkanes rings of CH2 units, (CH2)n, or CnH2n Structure is shown as a regular polygon with the number of vertices equal to the number of C’s (a projection of the actual structure) cyclopropane cyclobutane cyclohexane cyclopentane Naming Cycloalkanes Count the number of carbon atoms in the ring and the number in the largest substituent chain. If the number of carbon atoms in the ring is equal to or greater than the number in the substituent, the compound is named as an alkyl-substituted cycloalkane For an alkyl- or halo-substituted cycloalkane, start at a point of attachment as C1 and number the groups on the ring so that the second substituent has as low a number as possible. Number the substituents and write the name See text for more details and examples 3 Drawing molecules You can use structural formulas as usual or condensed formulas or line formulas. 9 8 5 1 7 3 6 4 2 Why is the above numbered incorrectly? What are their names? Hydrocarbons : Alkenes Carbon atoms have the ability to bond with other atoms with single, double, or even triple bonds. When carbon bonds to another carbon with a double bond, and only carbon and hydrogen atoms are in a compound it’s termed an alkene. Ethylene(ethene) is the simplest alkene. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/ Ethylene.html Alkynes Alkynes are hydrocarbons which contain a triple bond between carbons. Alkynes end in “yne”. Ethyne, Propyne, Butyne, etc. Practice Diagram the following hydrocarbons: a) Propene b) Butyne c) 2 hexene d) 2 - octyne Isomers Diagram the following hydrocarbons : a) Butane b) 2-methyl propane • The molecular formula for both of these is C4H10 • Even though the formula is the same the properties of these compounds is very different. • This is an example of isomers. Isomers are compounds with the same formula but different chemical and physical properties. (Boiling point, etc…) Practice Diagram a pentane molecule, and two isomers of this molecule. Name each isomer. Aromatic Hydrocarbons Hydrocarbons can also form ring structures. The simplest would be cyclopropane, cyclobutane, and cyclopentane. When six carbons form a ring we enter a new class of hydrocarbons called “aromatic” hydrocarbons. Benzene is the first member of aromatic hydrocarbons. Resonance occurs when two or more equally valid structures can be drawn for a molecule benzene exhibits resonance • explains unique properties of benzene and other aromatics – benzene is perfectly flat (electrons are delocalized, in other words, they are not fixed to one carbon but can move around) – bending or twisting of the aromatic molecule would disrupt the electron sharing and the stability of the molecule Properties of Benzene Molecular formula of benzene, C6H6, is based on its percent composition and molar mass MPbenzene = 5.5°C, BPbenzene=80.1°C Non-polar molecule Very unreactive with halogens Does not undergo addition reactions. All carbon-to-carbon bonds in benzene are the same length (determined by x-ray diffraction) Empirical evidence shows that all carbons are identical and that each carbon is bonded to one hydrogen Naming Aromatics 1. Number the carbons around the ring to give branches the lowest number possible. 2. Name the branches and end with the parent “benzene” 3. If benzene is a branch, use the prefix “phenyl” Some examples CH3 CH3 CH3 CH2CH3 1,2-dimethylbenzene CH3 CH3 CH2 CH2 CH CH CH3 methylbenzene ethylbenzene toluene 3-methyl-2-phenylhexane Hydrocarbon Summary At this point we’ve concluded our study of hydrocarbons. Below is a summary of the hydrocarbon compounds we’ve studied: Alkanes Alkenes Alkynes Branched alkanes, alkenes, alkynes Cyclic hydrocarbons Aromatic hydrocarbons Organic Compounds Hydrocarbons are used to synthesize a large amount of different organic compounds. In addition some of these organic compounds are naturally produced in living things. By adding substances and breaking bonds the hydrocarbon can become a new “class” of organic compound. Organic Compounds The organic compounds we will study include: Alcohols * sugars Aldehydes * starches Amine’s * lipids Carboxylic Acids (Organic Acids) Esters * proteins Ethers Ketones Fractional Distillation of Crude Oil (physical processes) Boiling points are used to separate the hydrocarbons. The smaller the hydrocarbon the further it travels up the tower. Larger molecules can go to the cracking process. Chemical Processes Catalytic cracker. The feedstock of long-chain hydrocarbons (1) is mixed with hot catalyst (2) and vaporized. The vapor/powder mixture is carried to the reactor where the cracking reactions occur. Cyclones (3) extract the cracked hydrocarbon vapor and pass it to the fractionating column where it is fractionated, yielding petroleum gases and gasoline (4), light gas oil (5), medium gas oil (6), and heavy gas oil (7). Spent catalyst meanwhile is mixed with steam (8) and carried in a current of hot air (9) to the catalyst regenerator where it is cleaned and recycled (10. Waste gases are drawn off (11) and vented. Other processing in Refining Solvent Extraction A physical process A solvent is used to selectively dissolve and separate desirable products or to remove impurities. Catalytic Reforming and Alkylation Catalytic Reforming Alkylation (isomerization) A chemical process A chemical process Changes straight chain Changes straight chain alkanes in to benzene alkanes into branched or aromatic alkanes hydrocarbons. Branched alkanes can The aromatics can also burn better than burn better. straight chain alkanes. Hydrocracking uses H2 to break longer chains into smaller ones. Removing Sulfur from Gasoline 1. Gasoline is vaporized at 500 oC 2. Hydrogen Gas is injected and reacts with sulfur to form hydrogen sulfide gas 3. The mixture is cooled and the H2S(g) is extracted. 4. The H2S(g) is converted to liquid sulfur for use in fertilizers and asphalt. Combustion Organic compounds can undergo: •Complete Combustion • CxHy + O2 CO2 + H2O(g) This is exothermic producing heat and light •Incomplete Combustion • CxHy + O2 C or CO or CO2 + H2O(g) This occurs when amounts of oxygen are low, they can still be balanced as usual. Alcohols Alcohols can be produced 3 different ways. Alcohols are compounds with an OH functional group (Hydroxyl) on a carbon skeleton. C- C– OH Hydroxyl Group (Alcohol) Alcohol Properties Alcohols with up to 4 carbon atoms are soluble in water as a result of the OH group on the carbon chain. As more carbon atoms are added to the chain the solubility decreases. Alcohols have higher boiling points than do the hydrocarbons from which they are formed from. Types of Alcohols There are three types of alcohols: Primary, Secondary, and tertiary. These types of alcohols are determined by “where” the OH is on the carbon chain. Primary : OH is at the end of a carbon chain. Secondary: OH is in the middle, with 2 C atoms attached to the C with the OH. Tertiary : OH is in the middle with 3 C atoms attached to the C with the OH. Alcohol Types Diagram a primary alcohol below : ( ethanol) • Diagram a secondary alcohol below: (2 – butanol) * Diagram a tertiary alcohol below: 2-methyl-2-propanol Naming Alcohols Alcohols are named by finding their hydrocarbon skeleton and ending this with “ol”. The OH group is identified to which carbon in the chain it is attached to. Name the following alcohol and identify it as primary, secondary, or tertiary. Diols/Triols Alcohols can have more than one OH group on a hydrocarbon chain. Alcohols with two OH’s are called diols, and the prefix di is added before the “ol” in naming. Alcohols with three OH’s are called triols, and the prefix “tri” is added before the “ol” in naming. Write the structural formula for 1,2-ethanediol. This is also known as ethylene glycol or antifreeze. Naming and Classifying Alcohols 1) Draw the structural formula for the following alcohols and classify them: a) 3-hexanol b) methanol c) 1,2,3-propanetriol (glycerol) Alcohol Formation Alcohols can be produced three ways : 1) From using bacteria or yeast in the process of fermentation. (ethanol and carbon dioxide are the waste products of yeast as they eat sugar) 12% 2) Addition of water to an alkene. (with an acid catalyst) 3) Hydrolysis of a halocarbons. Alcohol Formation • Diagram the formation of ethanol from ethene + water ( with an acid catalyst H2SO4) * Diagram the formation of ethanol from the hydrolysis (splitting by water) of chloroethane. Helpful Websites for Alcohols http://dl.clackamas.cc.or.us/ch106-03/nomencla.htm http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA5/M AIN/HOME.HTM Halocarbons Halocarbons are organic compounds in which halogens have replaced hydrogen. Halocarbons are named as to where the halogens are attached, and how many halogens there are. The halogen prefix is used : fluoro, chloro, bromo, etc. Halocarbon Uses Halocarbons are used extensively as pesticides, insecticides, dry cleaning, and other areas. Many of the most toxic chemicals have been halocarbons. PCB’s : poly chlorinated biphenols, are toxic synthesized halocarbons. DDT : a halocarbon which DDT: 1,1,1-trichloro-2,2-bis(p- chlorophenyl) ethane was banned in 1972 PCB’s PCB’s are halocarbons which contain two phenols with chlorine on them. PCB’s have been shown to be accumulative in fatty tissue, and bioaccumulate. The biphenols typically can persist in soil for 15-25 years. Naming Halocarbons Draw the structure for the following : a) Trichloromethane (chloroform) b) Tetraiodomethane: c) 2-fluoro pentane Ethers Ethers are organic compounds which have an oxygen atom bonded to two different carbons. Ethers are named by naming the compound on each side and ending in “ether”. Or by writing the short version of each with “oxy” in the middle. Ethers were used anesthetics, but safer gases have been found. Small ethers are soluble in water, but larger ethers are insoluble. Applications of ethers are solvents, gasoline additive, etc. Naming Ethers • Draw the structural diagram for the following : a) Dimethyl ether b) methoxypentane c) Diethyl ether d) Diphenyl ether Aldehydes Aldehydes are organic compounds which have a carbonyl group(C=O) at the end of a carbon chain. Aldehydes are named by ending the molecule with an “al”. Diagram ethanal, and propanal below: Uses of Aldehydes Aldehydes are used as preservatives, flavorings, perfumes, etc. Vanilla flavoring and cinnamon are natural aldehyde flavors. Ethanol is converted to acetaldehyde (propanal) in the human body. Ketones Ketones are a class of organic compounds with a carbonyl group (C=O) in the middle of a carbon chain. (Ketones are never alone) Propanone is the simplest ketone and is known as acetone. Acetone is a top 50 industrial chemical. Acetone is a common solvent for nonpolar substances. (fingernail polish remover) To name ketones end the carbon chain in “one”. Organic Acids (Carboxylic Acids) Carboxylic acids are a group of organic compounds which have a (COOH) functional group. Carboxylic or organic acids are weak acids. Examples are : acetic acid, citric acid, benzoic acid, etc. To name these acids use the carbon chain root : and add the suffix “oic” and the word acid. Naming Organic Acids Draw the structure for the following organic acids: a) Methanoic acid b) Ethanoic acid c) Butanoic acid d) Propanoic acid Properties of Organic Acids Methanoic acid (formic acid) is the acid in bee and ant stings. Ethanoic acid is acetic acid, found in vinegar Small chain organic acids are soluble in water. Lactic acid is an organic acid which builds up in body cells. Ascorbic acid (Vitamin C) is found in citrus fruits and tomatoes. Bacteria reacts butter into butanoic acid. (rancid butter) Esters Esters are organic compounds formed when an alcohol is added to an organic acid. Esters have distinctive odors. Esters have the functional group : (COOC) Esters are named by naming the alcohol name first ending in “yl”, then the acid name is given ending in “oate”. When an ester is synthesized from an alcohol and organic acid, the alcohol gives off the (O) atom , and the acid gives two (H) atoms to form water. Esters Diagram the reaction of ethanoic acid with methanol. Name the ester which forms. Esters Draw the structural formula for the following esters: a) Ethyl butanoate b) pentyl ethanoate Amines An amine is an organic compound which contains an “amino” functional group. An amino functional group is NH2 Amines can contain several amino functional groups. Amines Amines are named by adding the suffix “amine” to the root name of the hydrocarbon. Amines are also named by naming the hydrocarbon ending in “yl” with the suffix “amine”. Amines Amines are important Amino Group biological compounds. Amino acids which make up proteins contain an amino group along with an organic acid group. Amines are found in DNA. Amines are the basis of several addictive drugs : nicotine, cocaine, and Methamphetamine amphetamines. Naming Amines Draw the structure for the following amines. a) Butanamine b) pentylamine Amides Amides are produced when amines are added to an organic acid. Amides have an amino group and a carbonyl group attached to an end carbon. Amides are by adding the suffix “amide” to the end of the hydrocarbon root. Amides Amides are found in biological compounds and in some synthetic polymers such as nylon. Nylon : a polymer with an amide group in the chain. Naming Amides Draw the structure of ethanamide. What is the name of the amide above? Organic Compound Summary • The following are the organic compounds we’ve studied. They are identified by their “functional group”. • Hydrocarbons * Esters • Alcohols * Organic Acids • Ethers * Amines • Ketones * Amides • Aldehydes * Halocarbons Polymers Small organic molecules (monomers) can be reacted to form long organic molecules (polymers) Example of polymers are : polyethylene (plastic), polyvinylchloride (PVC), nylon, polyester, etc. Polymers can be formed by a condensation reaction (water is produced) Polymers Polymers can be formed by an elimination reaction, where a simple molecule (water, etc.) is removed and a new compound is formed. PVC : polyvinyl chloride polymer Polymers Other polymers include Teflon Polystyrene Proteins Lipids Starches Polytetrafluoroethene :teflon monomer Polymers Nylon is a polymer involving an amide monomer. Nylon was synthesiszed in the 1930’s and named after the cities of New York and London. Nylon is produced by adding an organic acid to an amine. Nylon has many uses.
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