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The History of Organic Chemistry The name organic chemistry came from the word organism. Prior to 1828, all organic compounds had been obtained from organisms or their remains. The scientific philosophy back then was that the synthesis of organic compounds could only be produced within living matter while inorganic compounds were synthesized from non-living matter. A theory known as "Vitalism" stated that a "vital force" from living organisms was necessary to make an organic compound. 1828, a German chemist Friedrich Wöhler (1800-1882) amazed the sience community by using the inorganic compound ammonium cyanate, NH4OCN to synthesize urea, H2NCONH2, an organic substance found in the urine of many animals. This led to the disappearance of the "Vitalism" theory. Today, chemists consider organic compounds to be those containing carbon and one or more other elements, most often hydrogen, oxygen, nitrogen, sulfur, or the halogens, but sometimes others as well. Organic chemistry is defined as the chemistry of carbon and its compounds. The Uniqueness of Carbon There are more carbon compounds than there are compounds of all other elements combined. Plastics, foods, textiles, and many other common substances contain carbon. With oxygen and a metallic element, carbon forms many important carbonates, such as calcium carbonate (limestone) and sodium carbonate (soda). Certain active metals react with it to make industrially important carbides, such as silicon carbide, an abrasive known as carborundum, and tungsten carbide, an extremely hard substance used for rock drills and metalworking tools. The great number of carbon compounds is possible because of the ability of carbon to form strong covalent bonds to each other while also holding the atoms of other nonmetals strongly. Carbon atoms have the special property to bond with each other to form chains, ring, spheres, and tubes. Chains of carbon atoms can be thousands of atoms long, as in polyethylene. Polyethylene chain: H H H H H H H H H H H | | | | | | | | | | | H-C-C-C-C-C-C-C-C-C-C-C-etc. | | | | | | | | | | | H H H H H H H H H H H Structural Isomers Isomers are classified as structural isomers, which have the same number of atoms of each element in them and the same atomic weight but differ in the arrangement of atoms in the molecule. For example, there ware two compounds with the molecular formula C2H6O. One is ethanol (also called ethyl alcohol), CH3CH2OH, a colorless liquid alcohol; the other is dimethyl ether, CH3OCH3, a colorless gaseous ether. Among their different properties, ethanol has a boiling point of 78.5°C and a freezing point of -117°C; dimethyl ether has a boiling point of 25°C and a freezing point of -138°C. Ethanol and dimethyl ether are isomers because they differ in the way the atoms are joined together in their molecules. Aliphatic Hydrocarbons Hydrocarbons which do not contain a benzene ring are called aliphatic hydrocarbons. Those which do contain benzine are called aromatic hydrocarbons. HyperPhysics*****Chemistry Index Carbon compounds Chemistry concepts R Go Back Nave Alkanes Alkanes are a hydrocarbon family that with carbon atoms that are only bonded to each other with single bonds. Alkanes have the general molecular formula, CnH2n+2, where n = number of carbon atoms in the alkane molecule. A normal hydrocarbon alkane is one where all the carbon atoms in the molecule are in a "continuous" chain. A continuous chain does not necessarily mean that the carbons are in a straight line. The carbons can be in a "zig zag" chain as long as the chain is connected by a carbon atom. The simplest alkane is methane, CH4. It is made from one carbon atom bonded to four hydrogen atoms. The table below shows the first ten alkanes. IUPAC name Number of Molecular Structural Prefix Carbons Formula Formula Methane 1 Meth- CH4 CH4 Ethane Eth- CH3CH3 2 C2H6 Propane 3 Prop- C3H8 CH3CH2CH3 Butane But- C4H10 CH3(CH2)2CH3 Pentane 5 Pent- C5H12 CH3(CH2)3CH3 Hexane Hex- C6H14 CH3(CH2)4CH3 Heptane 7 Hept- C7H16 CH3(CH2)5CH3 Octane Oct- C8H18 CH3(CH2)6CH3 Nonane 9 Non- C9H20 CH3(CH2)7CH3 Decane Dec- CH3(CH2)8CH3 4 6 8 10 C10H22 Alkyl Groups An alkyl is basically an alkane minus one of its hydrogen atoms. For example: H H | remove one H | H-C-H ============> H-C- or | | H H methane methyl H H | | H-C-C-H | | H H ethane H H remove one H | | ============> H-C-C| | H H ethyl CH3- or CH3CH2- Alkyl names are used to name branched alkanes. Any branch in an alkane would be named as the number of carbons + "yl". Rules for naming Alkanes 1. First, identify the longest continuous chain in the link of carbon atoms, also known as the parent chain. The parent chain does not have to be connected in a straight line, it could be in "zig zag" lines only if it proves to have the most amount of carbon atoms in its chain. Number the carbons in the parent chain starting from the end closest to the branch(es) so that the substituents will have the smallest possible numbers. 2. Next, find each alkyl branch and assign it a number according to which carbon atom it is attached to. The name for the alkyl branch is followed by "-yl" to indicate the number of carbon atoms are in a branch. 3. List the substituents (with their carbon number) in alphabetical order followed by the name of the parent alkane. In some cases when there are more than one of a given substituent use the prefixes di-, tri-, tetra-. Prefixes are not used to determine alphabetical order. The structural format should look like this: (number of location)-(branch name)(name of parent chain) 4. Use commas between numbers and dashes between numbers and words in naming the IUPAC formulas. Do not leave spaces in the name. Cycloalkanes Cycloalkanes are alkanes in which a bond is formed between the two terminal carbons in the chain to for a cyclical or ring structure. The prefix cyclo- is written before the name designating the carbon number in the ring (e.g. cyclohexane). 1. Substituents are named similarly to straight-chained alkanes. The carbons in the ring are numbered so that the substituents have the smallest numbers. 2. Add the prefix cyclo- to the alkane name Example: CH2 / \ CH2-CH2 cyclopropane CH2-CH2 | | CH2-CH2 cyclobutane Alkenes Alkenes are hydrocarbons that contain one or more carbon-carbon double bonds. Alkenes with only one double bond have the general formula CnH2n Naming alkenes has the same format as naming alkanes, but be sure to change the -ane ending on the parent name to -ene ending. This shows that the compound is an alkene. 1. Determine the longest continuous chain of carbons that have the double bond between two of its carbons. The parent chain must contain the double bond. 2. Number the carbons in the chain so that the double bond would be between the carbons with the lowest designated number. Numbering could start either from the left end or right end of the chain. The location of the double bond, not the location of the branches are used for numbering the alkene. 3. Identify the various branching groups attached to this continuous chain of carbons by name. 4. The format is as follows: (location of branch)-(branch name)(parent chain) Example: CH3CH2CH=CH2 4 3 2 1 1-butene CH3CH=CHCH3 1 2 3 4 2-butene CH3 CH3 | | CH3CH2CHCH2CH=CCH3 7 6 5 4 3 21 2,5-dimethyl-2-heptene Geometric Isomers In alkanes, rotational freedom is possible but for alkenes, due to the carbon-carbon double bond, it is impossible to rotate the bond without breaking it. Geometric isomers are isomers that differ from each other based on the position of the attached groups relative to the double bond. Two substituents that are on the same side of the double bond is called cis, meaning "same", two substituents that are on the same side of the double bond is called trans, meaning "across". Organic Compounds are categorized by the Functional Groups that follow below… Alkynes Alkynes are hydrocarbons that have at least one triple covalent bond between two carbon atoms. The general formula for the Alkyne CnH2n-2. Similarly, alkynes are named just like alkenes only with the -yne ending instead of the -ene ending in naming compounds. 1. Determine the longest continuous chain of carbons that have the triple bond between two of its carbon atoms. 2. Number the carbons in the chain so that the triple bond would be between the carbons with the lowest designated number. This means that you have to decide whether to number beginning on the right end or left end of the chain in order to obtain the smallest possible numbers. 3. Identify the various branching groups attached to this continuous chain of carbons by name. 4. The format is as follows: (location of branch)-(branch name)(parent chain) Example Aromatics Aromatics are carbon compounds that have benzene-like properties. The term "aromatic" came to be because earlier compounds found with the rings had pleasant fragrances, but it turns out that the ring has nothing to do with smell. Benzene, back then, had special properties and fascinated scientists for many years. At last, a structural model was proposed and accepted as the benzene ring. Aromatics consists of a benzene ring located anywhere within the molecular structure. If an alkyl group substitutes a hydrogen atom on the benzene ring, the structure is similarly named like an branched alkane. 1. Obtain the smallest possible numbers to indicate the location of the branched alkanes. In order to obtain this, numbering starts at one of the substituents and continues either clockwise or counterclockwise to get the smallest possible numbers. If there is only one substituent, numbering is not required. 2. Identify the various branching groups attached to this continuous chain of carbons by name. 3. The format is as follows: (location of branch)-(branch name)(parent chain) If a benzene ring is considered a branch(in larger molecules), then the benzene ring is called a phenyl group. In this case, the alkane becomes the parent chain and the phenyl thus becomes a branch of the alkane structure. Eg. 1-phenylbutane or benzene methylbenzene (toluene) ethylbenzene Alcohols All alcohols contain the hydroxyl functional group, -O-H, attached to single bonded hydrocarbons (alkanes). Alcohol have the general formula R-OH where R represents any chain of carbon and hydrogen atoms. The four most common alcohols are: CH3OH methanol CH3CH2OH ethanol CH3CH2CH2OH 1-propanol OH | CH3CHCH3 2-propanol Alcohols use the same formats as alkanes. To name alcohols, 1. Determine the parent chain. The parent chain must be the longest that includes the carbon holding the OH group. 2. Number according to the end closest to the -OH group regardless of where alkyl substituents are. 3. The format is as follows: (location of branch)-(branch name)-(location of OH group)-(parent chain) 4. Change the parent chain -e ending and replace it with an -ol. Example: H | H H H-C-H H | | | | H-C-C---C---C-H | | | | H O H H | H Parent chain: butane -OH group location: 2 Substituents locations: 3-methyl Alkane name: 3-methylbutane Alcohol name: 3-methyl-2-butanol Alchohols containing more than one hydroxyl group are also called polyalcohols. Polyalcohols are named similarly to alcohols, with the exception of the prefix di-, tri-, etc before the -ol ending. Example: H H | | H-C-C-H | | OH OH 1,2-ethanediol H H H | | | H-C-C-C-H | | | OH OH OH 1,2,3-propanetriol Carboxylic Acids Carboxylic acids is a family of organic compounds that contains the carboxyl group, -COOH. which consists of a carbon atom joined to an oxygen atom by a double bond and to a hydroxyl group, OH, by a single bond. Carboxyl group 1. Determine the parent chain. The parent chain must include the carboxyl carbon. 2. Number starting at the end closest to the carboxyl group. 3. The name of the alkane (parent chain) is changed by replacing the -e with -oic followed by the word "acid". Example: HCOOH methanoic acid CH3COOH CH3CH2CH2COOH ethanoic acid (acetic acid) butanoic acid Esters Esters are a group of organic compounds with a general formula R1CO2R2 (where R1 and R2 are alkyl groups) that are formed, along with water, by the reaction of acids and alcohols. Natural occurring esters of organic acids in fruits and flowers give them their distinctive odors. It also also used for food aroma and taste, perfumes, synthetic fibres, and solvents. To name esters, 1. Identify the alkyl group that is attached to the oxygen atom 2. Number according to the end closest to the -CO- group regardless of where alkyl substituents are. 3. Determine the alkane that links the carbon atoms together. If there is a separation of a continuous link of carbon atoms due to the oxygen atom, individually name the two alkanes before and after the oxygen atom. The longer structural alkane is the one that should contain the carbonyl atom. 4. The format is as follows: (alkane further from carbonyl) (alkane closest to carbony)(parent chain) 5. Change the parent chain -e ending and replace it with an -oate. Example: CH3COOC7H14CH3 octyl ethanoate Synthesis The synthesis of aspirin is classified as an esterification reaction. Salicylic acid is treated with acetic anhydride, an acid derivative, causing a chemical reaction that turns salicylic acid's phenol group into an acetyl group, (R-OH → R-OCOCH3). This process yields aspirin and acetic acid, which is considered a byproduct of this reaction. Small amounts of sulfuric acid (and occasionally phosphoric acid) are almost always used as a catalyst. This method is commonly employed in undergraduate teaching labs.[58] Formulations containing high concentrations of aspirin often smell like vinegar.[59] This is because aspirin can decompose through hydrolysis in moist conditions, yielding salicylic acid and acetic acid.[60] The acid dissociation constant (pKa) for acetylsalicylic acid is 3.5 at 25 °C.[61] Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's stockings ("nylons"; 1940). It is made of repeating units linked by peptide bonds (another name for amide bonds) and is frequently referred to as polyamide (PA). Nylon was the first commercially successful synthetic polymer. There are two common methods of making nylon for fiber applications. In one approach, molecules with an acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on each end. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. These are formed into monomers of intermediate molecular weight, which are then reacted to form long polymer chains. Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II. It replaced silk in military applications such as parachutes and flak vests, and was used in many types of vehicle tires. Nylon fibers are used in many applications, including fabrics, bridal veils, carpets, musical strings, and rope. Solid nylon is used for mechanical parts such as machine screws, gears and other low- to medium-stress components previously cast in metal. Engineering-grade nylon is processed by extrusion, casting, and injection molding. Solid nylon is used in hair combs. Type 6/6 Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the most common commercial grade of molded nylon. Nylon is available in glass-filled variants which increase structural and impact strength and rigidity, and molybdenum sulfide-filled variants which increase lubricity. Aramids are another type of polyamide with quite different chain structures which include aromatic groups in the main chain. Such polymers make excellent ballistic fibres.