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Nomenclature of Organic compounds Prof. Dr. Ashraf El- Bassuony Organic and Biological Chemistry  References. John D. Bookstaver Fundamentals of Organic St. Charles Community Co...

Nomenclature of Organic compounds Prof. Dr. Ashraf El- Bassuony Organic and Biological Chemistry  References. John D. Bookstaver Fundamentals of Organic St. Charles Community College Chemistry 4th Edn. 2004, St. Peters, MO John McMurry  2006, Prentice Hall, Inc. Chemistry, The Central Science, http://www.chem.ucalgary.ca/co 10th edition urses/351/Carey5th/Carey.html http://www.chem.uic.edu/web1/ Theodore L. Brown; H. Eugene OCOL-II/WIN/STEREO.HTM LeMay, Jr.; and Bruce E. Bursten http://www.colby.edu/chemistry/ OChem/DEMOS/Chirality.html Organic Chemistry 5th Edn. 2007, http://webhost.bridgew.edu/fgor Paula Y. Bruice, Prentice Hall, Inc. ga/Stereochem/default.htm Organic Chemistry 5th Edn. 2005, Francis A. Carey, Organic and McGraw-Hill Publishing Biological Chemistry ORGANIC FUNCTIONAL GROUPS Carboxylic Alcohol Acid Aldehyde Ester Halide Ketone -F, Br, Cl, I Amine Ether Methyl- Ethly- -CH2-CH Organic and 3 Biological Chemistry Organic Chemistry Methane is a tetrahedral molecule Organic and Biological Chemistry Structure of Carbon Compounds There are three hybridization states and geometries found in organic compounds:  sp3 Tetrahedral  sp2 Trigonal planar  sp Linear Organic and Biological Chemistry  Hydrocarbons Four basic types:  Alkanes  Alkenes  Alkynes  Aromatic hydrocarbons Organic and Biological Chemistry  Alkanes Only single bonds. Saturated hydrocarbons.  “Saturated” with hydrogens. Organic and Biological Chemistry  Formulas Lewis structures of alkanes look like this. Also called structural formulas. Often not convenient, though… Organic and Biological Chemistry  Formulas …so more often condensed formulas are used. Organic and Biological Chemistry  Properties of Alkanes Only van der Waals force: London force. Organic and Boiling point increases with length of chain. Biological Chemistry  Structure of Alkanes Carbons in alkanes sp3 hybrids. Tetrahedral geometry. 109.5° bond angles. Organic and Biological Chemistry Structure of Alkanes Only -bonds in alkanes Free rotation about C—C bonds. Organic and Biological Chemistry Isomers Have same molecular formulas, but atoms are bonded in different order. Organic and Biological Chemistry  Organic Nomenclature Three parts to a compound name:  Base: Tells how many carbons are in the longest continuous chain. Organic and Biological Chemistry  Organic Nomenclature Three parts to a compound name:  Base: Tells how many carbons are in the longest continuous chain.  Suffix: Tells what type of compound it is. Organic and Biological Chemistry  Organic Nomenclature Three parts to a compound name:  Base: Tells how many carbons are in the longest continuous chain.  Suffix: Tells what type of compound it is.  Prefix: Tells what groups are attached to chain. Organic and Biological Chemistry  ORGANIC PREFIXES Number of Organic Inorganic Carbon Atoms Prefix Prefix 1 Meth- Mono- 2 Eth- Di- 3 Prop- Tri- 4 But- Tetra- 5 Pent- Penta- 6 Hex- Hexa- 7 Hept- Hepta- 8 Oct- Octa- 9 Non- Nona- Organic and Dec- Deca- Biological 10 Chemistry  STRAIGHT CHAIN ALKANES #C Name Formula Atoms 1 Methane CH4 2 Ethane CH3- CH3 3 Propane CH3- CH2-CH3 4 Butane CH3- CH2-CH2-CH3 5 Pentane CH3- CH2-CH2-CH2-CH3 6 Hexane CH3- CH2-CH2-CH2-CH2-CH3 7 Heptane CH3- CH2-CH2-CH2-CH2-CH2-CH3 8 Octane CH3- CH2-CH2-CH2-CH2-CH2-CH2-CH3 9 Nonane CH3- CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3 10 Decane CH3- CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH 3 and Organic Biological Chemistry  Summary: IUPAC Rules for Alkane Nomenclature 1. Find and name the longest continuous carbon chain. This is called the parent chain. (Examples: methane, propane, etc.) 2. Number the chain consecutively, starting at the end nearest an attached group (substituent). 3. Identify and name groups attached to this chain. (Examples: methyl-, bromo-, etc.) 4. Designate the location of each substituent group with the number of the carbon parent chain on which the group is attached. Place a dash between numbers and letters. (Example: 3-chloropentane) 5. Assemble the name, listing groups in alphabetical order. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing. Place a comma between multiple Organic and Biological numbers. (Example: 2,3-dichloropropane) Chemistry Step 1. Find the parent chain. Where is the longest continuous chain of carbons? Organic and Biological Chemistry  Endings Alkanes (all C-C single bonded parent chain) end in –ane Methane CH4 Ethane C2H6 Propane C3H8 Attached carbon groups (substituents) end in –yl Methyl CH3 - Ethyl CH3CH2- Organic and Propyl CH3CH2CH2 – Biological Chemistry 3-ethylpentane  Step 2. Number the parent chain. Number the parent chain so that the attached groups are on the lowest numbers Methyl is on carbon #2 of the parent chain Methyl is on carbon #4 of the parent chain GREEN is the 1 2 3 4 right way for this 5 one! 5 4 3 2 1 18 2 7 36 1 2 3 4 5 72 81 7 66 5 4 3 and Organic Biological Groups on 4, 6, on 3 1 Groups on 2 Groups Chemistry 4Groups 5 5 4 on 2, 3, and 5 Step 3. Name the attached groups. Carbon (alkyl) groups Methyl CH3 - Ethyl CH3CH2- Propyl CH3CH2CH2 – Halogens Fluoro (F-) Chloro (Cl-) Bromo (Br-) Iodo (I-) Organic and Biological Chemistry Organic and Biological Chemistry  Rules for Naming Alkanes Positions of substituent groups are specified by numbering the longest chain sequentially. C  C-C-C-C-C-C 3-methylhexane Start numbering at the end closest to the branching Organic and Biological Chemistry  Normal vs Branched Alkanes Normal alkanes consist of CH2 CH2 continuous chains of CH3 CH2 CH3 carbon atoms Alkanes that are NOT continuous chains of carbon atoms contain CH2 CH3 branches CH3 CH The longest continuous chain of carbons is called CH3 the parent chain Organic and Biological Chemistry Step 4. Designate where the group is attached to the parent chain. Use the numbers of the parent chain from step 2 to designate the location of the attached groups to the parent chain. 2-methyl 1 2 3 4 5 Organic and Biological Chemistry  Example : Show the structural formula of 2,2-dimethylpentane The parent chain is indicated 2 4 by the ROOT of the name - 1 CH2 3 CH2 5 “pentane”. This means there CH CH2 CH3 3 are 5 carbons in the parent chain. “dimethyl” tells us that there are CH3 TWO methyl branches on the 4 parent chain. A methyl branch is C CH2 made of a single carbon atom. CH3 CH2 CH3 “2,2-” tell us that BOTH methyl 1 3 5 CH3 branches are on the second Organic and Biological carbon atom in the parent chain. Chemistry  Example: Structural formula of 3-ethyl-2,4-dimethylheptane? The parent chain is indicated 2 4 by the ROOT of the name - 1 CH2 3 CH2 5 “heptane”. This means there CH3 CH2 CH2 are 7 carbons in the parent chain. H2C 6 7 CH3 CH3 CH3 “2,4-dimethyl” tells us there are CH CH TWO methyl branches on the CH3 CH CH2 parent chain, at carbons #2 and #4. CH2 CH2 “3-ethyl-” tell us there is anOrganic ethyl and CH3 CH3 branch (2-carbon branch) on Biological Chemistry carbon #3 of the parent chain. Example: 2,3,3-trimethyl-4-propyloctane The parent chain is indicated by the ROOT of the name - 3 5 “octane”. This means there 4 6 2 are 8 carbons in the parent 7 chain. 1 8 CH3 3 5 “2,3,3-trimethyl” tells us there are 2 4 CH3THREECmethyl branches CH2 - one on 6 CH #2 andCH carbon two on carbonCH2#3. 7 CH3 1 8 “4-propyl-” CH3 tellCH us there 2 is CH a propyl 2 branch (3-carbon branch) CH2 onOrganic CH3 and carbon #4 of the parent chain.Biological Chemistry CH3  Example : Name the molecules shown CH3 parent chain has 5 carbons - “pentane” CH2 CH two methyl branches - start counting from the right - #2 CH3 CH CH3 and #3 2,3-dimethylpentane CH3 parent chain has 8 carbons - “octane” two methyl branches - start counting from the left - #3 and #4 4 3 5 one ethyl branch - #5 name branches alphabeticallyOrganic and Biological 5-ethyl-3,4-dimethyl octane Chemistry Step 5. Alphabetize the groups, combine like groups, and assemble. The prefixes di, tri, tetra etc., used to designate several groups of the same kind Prefixes are not considered when 1,1,1-trichloro- 1,1-dichloro- alphabetizing (Example: 1- 1,1- dimethyl = m for fluoromethane difluorometh alphabetizing) ane Parent chain goes LAST Organic and Biological Chemistry  Draw Some Simple Alkanes 2-methylpentane 3-ethylhexane 2,2-dimethylbutane 2,3-dimethylbutane Organic and Biological Chemistry  Order of Priority IN A TIE, halogens get the lower number before alkyl groups 4-chloro-2-methylpentane or 2-chloro-4-methylpentane? Organic and Biological Chemistry  C C C H Types of Carbon Atoms H Primary carbon (1o) C C H  a carbon bonded to one other carbon H H Secondary carbon (2o) H C C C  a carbon bondedCto C C two other carbons H H H H C C Tertiary carbon (3o) H C C C H C Organic and  a carbon bonded to C C H Biological three other carbonsC C H C Chemistry Organic and Biological Chemistry Organic and Biological Chemistry  3 H3 CH CH CH2 CH CH3 H3 C CH3 CH CH Alkanes 2 3 CH3 Example: Name the following compounds: CH3 CH3 CHCH3 CH CH3 CH3 CH CH CH2 CH CH3 CH3 C CH2 CH2Br CH3 C CH3 CH2CH3 CH2CH3 CH3 Organic and Biological Chemistry  Alkanes Example: Write the condensed structure for the following compounds: 3,3-dimethylpentane 2-methyl-4-sec-butyloctane 1,2-dichloro-3-methylheptane Organic and Biological Chemistry  Reactions of alkanes Combustion reactions 2C4H10 + 13 O2 8CO2 + 10 H2O(g) Substitution Reactions CH4 + Cl2 CH3Cl + HCl CH3Cl + Cl2 CH2Cl2 + HCl CH2Cl2 + Cl2 CH Cl3 + HCl h Organic and CHCl 3  Cl 2 CCl 4  HCl Biological Chemistry  Dehydrogenation Reactions CH3CH3 CH2 CH2 Ethylene Organic and Biological Chemistry  Cyclic alkanes A cycloalkane is made of a hydrocarbon chain that has been joined to make a “ring”. 109.5° bond angle H2 60° bond angle CH2 C unstable!! CH3 CH3 H2C CH2 n-propane cyclopropane C3H8 C3H6 Note that two hydrogen atoms were lost in forming the ring Organic and Biological What is the general formula for a cycloalkane? Chemistry  Cycloalkanes Carbon can also form ringed structures. Five- and six-membered rings are most stable.  Can take on conformation in which angles are very close to tetrahedral angle.  Smaller rings are quite strained. Organic and Biological Chemistry  Naming Organic Compounds Functional Functional Identifier Identifier Group Group Alkane -ane Ring cyclo- Alkene -ene Ketone -one Alkyne -yne Aldehyde -al Fluoro-, Chloro- Carboxylic Halides -oic acid Bromo-, Iodo- Acid Alcohol -ol Amine amino- CH3- methyl- Ester -ate Organic and CH3CH2- ethyl- Biological Chemistry  Nomenclature of Alkenes Chain numbered so double bond gets smallest possible number. cis- alkenes have carbons in chain on same side of molecule. trans- alkenes have carbons in chain on opposite side of molecule. Organic and Biological Chemistry  Unsaturated hydrocarbomns 22.2 Alkenes and Alkynes Alkenes: hydrocarbons that contain a carbon-carbon double bond. [CnH2n] C=C Ethene CC=C propene Alkynes: hydrocarbons containing a carbon-carbon triple bond. [CnH2n-2] C C Ethyne CCCCC 2-pentyne Organic and Biological Chemistry  Alkenes & Alkynes Alkenes are The suffix for the hydrocarbons that parent alkane chains contain at least one are changed from carbon-carbon “ane” to “ene” and double bond “yne” Alkynes are e.g. ethene, ethyne hydrocarbons that Where it is ambiguous, contain at least one the BONDS are carbon-carbon triple numbered like bond branches so that the location of the multiple Organic and Biological bond may be indicatedChemistry  Alkenes, CnH2n Cycle formation isn’t the only possible result of dehydrogenation. Adjacent C’s can double bond, C=C, making an (unsaturated) alkene. Sp2 Organic and Biological Chemistry The Bonding in Ethylene Organic and Biological Chemistry  Nomenclature for Alkenes 1.Root hydrocarbon name ends in -ene C2H4; CH2=CH2 is ethene 2.With more than 3 carbons, double bond is indicated by the lowest numbered carbon atom in the bond. C=CCC is 1-butene Organic and Biological Chemistry  Cis and Trans Isomers Double bond is fixed Cis/trans Isomers are possible CH3 CH3 CH3 CH = CH CH = CH cis trans CH3 Organic and Biological Chemistry  Properties of Alkenes Structure also affects physical properties of alkenes. Organic and Biological Chemistry  Addition Reactions Weaker  bonds are broken and new (stronger)  bonds are formed to atoms being added. Organic and Biological Chemistry  Hydrogenation Adds a hydrogen atom to each carbon atom of a double bond H H H H Ni H–C=C–H + H2 H–C–C–H CH3-CH3 H H Organic and ethene ethane Biological Chemistry  Halogenation Adds a halogen atom to each carbon atom of a double bond H H H H Ni H–C=C–H + Cl2 H–C–C–H Cl Cl Organic and ethene dichloro ethane Biological Chemistry  Halogenation Reactions CH2 CHCH2CH2CH2 + Br2 CH2Br CHBrCH2CH2CH2 1,2-dibromopentane Organic and Biological Chemistry  Alkynes, CnH2n–2 Carbon-carbon triple bonds Names end in -yne HCCH ethyne(acetylene) HCC-CH3 propyne Organic and Biological Chemistry The Bonding in Acetylene Organic and Biological Chemistry  Naming Alkenes and Alkynes When the carbon chain has 4 or more C atoms, number the chain to give the lowest number to the double or triple bond. 1 2 3 4 CH2=CHCH2CH3 1-butene CH3CH=CHCH3 2-butene  CH3CH CHCH3 2-butyne Organic and Biological Chemistry  Nomenclature of Alkynes 4-methyl-2-pentyne Analogous to naming of alkenes. Suffix is -yne rather than –ene. Organic and Biological Chemistry  Question Write the IUPAC name for each of the following unsaturated compounds: 2-pentyne A. CH3CH2CCCH3 CH3 B. CH3C=CHCH3 2-methyl-2-butene Organic and Biological Chemistry  Question Name the following compound CH3CH2C CCHCH2CH3 CH2 CH3 1 2 3 4 5 6 7 CH3CH2C CCHCH2CH3 CH2 CH3 Organic and Biological 5-ethyl-3-heptyne Chemistry  Reactions of Alkynes Undergo many of the same reactions alkenes do. As with alkenes, impetus for reaction is replacement of -bonds with -bonds. Organic and Biological Chemistry  Additions reactions:Hydrogenation and Halogenation Hydrogens and halogens also add to the triple bond of an alkyne. Br Br CH3C CCH2CH3 + Br2 CH3C CCH2CH3 Br Br Organic and Biological Chemistry  HALIDES Use the following names when adding a halogen (halide) group: Fluoro-, Chloro-, Bromo-, Iodo. EXAMPLE 1: EXAMPLE 2: Draw the structure and give the formula for 1,1,1-trichloroethane. Organic and Biological Chemistry To Name a Compound… 1. Find the longest chain in the molecule. 2. Number the chain from the end nearest the first substituent encountered. 3. List the substituents as a prefix along with the number(s) of the carbon(s) to which they are attached. Organic and Biological Chemistry To Name a Compound… If there is more than one type of substituent in the molecule, list them alphabetically. Organic and Biological Chemistry SAMPLE EXERCISE 25.1 Naming Alkanes Give the systematic name for the following alkane: Solution Analyze: We are given the structural formula of an alkane and asked to give its name. Plan: Because the hydrocarbon is an alkane, its name ends in -ane. The name of the parent hydrocarbon is based on the longest continuous chain of carbon atoms, as summarized in Table 25.1. Branches are alkyl groups, named after the number of C atoms in the branch and located by counting C atoms along the longest continuous chain. Solve: The longest continuous chain of C atoms extends from the upper left CH3 group to the lower left CH3 group and is seven C atoms long: The parent compound is thus heptane. There are two CH3 (methyl) groups that branch off the main chain. Hence, this compound is a dimethylheptane. To specify the location of the two methyl groups, we must number the C Organic and atoms from the end that gives the lowest number possible to the carbons bearing side chains. This means that we Biological should start numbering with the upper left carbon. There is a methyl group on carbon 3, and one on carbon 4. Chemistry The compound is thus 3,4-dimethylheptane. SAMPLE EXERCISE 25.1 continued PRACTICE EXERCISE Name the following alkane: Answer: 2,4-dimethylpentane Organic and Biological Chemistry SAMPLE EXERCISE 25.2 Writing Condensed Structural Formulas Write the condensed structural formula for 3-ethyl-2-methylpentane. Solution Analyze: We are given the systematic name for a hydrocarbon and asked to write its structural formula. Plan: Because the compound’s name ends in -ane, it is an alkane, meaning that all the carbon–carbon bonds are single bonds. The parent hydrocarbon is pentane, indicating five C atoms (Table 25.1). There are two alkyl groups specified, an ethyl group (two carbon atoms, C 2H5) and a methyl group (one carbon atom, CH3). Counting from left to right along the five-carbon chain, the ethyl group will be attached to the third C atom and the methyl group will be attached to the second C atom. Solve: We begin by writing a string of five C atoms attached to each other by single bonds. These represent the backbone of the parent pentane chain: C––C––C––C––C We next place a methyl group on the second C and an ethyl group on the third C atom of the chain. Hydrogens are then added to all the other C atoms to make the four bonds to each carbon, giving the following condensed structure: Organic and Biological Chemistry  Reactions of Alkynes Undergo many of the same reactions alkenes do. As with alkenes, impetus for reaction is replacement of -bonds with -bonds. Organic and Biological Chemistry SAMPLE EXERCISE 25.4 continued PRACTICE EXERCISE Draw the condensed structural formula for 4-methyl-2-pentyne. Answer: Organic and Biological Chemistry  Aromatic Hydrocarbons Cyclic hydrocarbons. p-Orbital on each atom.  Molecule is planar. Odd number of electron pairs in -system. Organic and Biological Chemistry  Aromatic Nomenclature Many aromatic hydrocarbons are known by their common names. Organic and Biological Chemistry Reactions of Aromatic Compounds Unlike in alkenes and alkynes, - electrons do not sit between two atoms. Electrons are delocalized; this stabilizes aromatic compounds. Organic and Biological Chemistry Reactions of Aromatic Compounds Due to stabilization, aromatic compounds do not undergo addition reactions; they undergo substitution. Hydrogen is replaced by substituent. Organic and Biological Chemistry Structure of Aromatic Compounds Two substituents on a benzene ring could have three possible relationships  ortho-: On adjacent carbons.  meta-: One carbon between them. Organic and  para-: On opposite sides of ring. Biological Chemistry Reactions of Aromatic Compounds Halogenation Friedel-Crafts Reaction Reactions of aromatic compounds often require a catalyst. Organic and Biological Chemistry Functional Groups Term used to refer to parts of organic molecules where reactions tend to occur. Organic and Biological Chemistry  Alcohols Contain one or more hydroxyl groups, —OH Named from parent hydrocarbon; suffix changed to -ol and number designates carbon to which hydroxyl is attached. Organic and Biological Chemistry Alcohols Much more acidic than hydrocarbons.  pKa ~15 for most alcohols.  Aromatic alcohols have pKa ~10. Organic and Biological Chemistry  Ethers Tend to be quite unreactive. Therefore, they are good polar solvents. Organic and Biological Chemistry Carbonyl Compounds Contain C—O double bond. Include many classes of compounds. Organic and Biological Chemistry  Aldehydes At least one hydrogen attached to carbonyl carbon. Organic and Biological Chemistry Ketones Two carbons bonded to carbonyl carbon. Organic and Biological Chemistry  Carboxylic Acids Have hydroxyl group bonded to carbonyl group. Tart tasting. Carboxylic acids are weak acids. CH3COOH Organic and Biological Chemistry Carboxylic Acids Organic and Biological Chemistry Esters Products of reaction between carboxylic acids and alcohols. Found in many fruits and perfumes. Organic and Biological Chemistry SAMPLE EXERCISE 25.6 Naming Esters and Predicting Hydrolysis Products In a basic aqueous solution, esters react with hydroxide ion to form the salt of the carboxylic acid and the alcohol from which the ester is constituted. Name each of the following esters, and indicate the products of their reaction with aqueous base. Solution Analyze: We are given two esters and asked to name them and to predict the products formed when they undergo hydrolysis (split into an alcohol and carboxylate ion) in basic solution. Plan: Esters are formed by the condensation reaction between an alcohol and a carboxylic acid. To name an ester, we must analyze its structure and determine the identities of the alcohol and acid from which it is formed. We can identify the alcohol by adding an OH to the alkyl group attached to the O atom of the carboxyl (COO) group. We can identify the acid by adding an H group to the O atom of the carboxyl group. We’ve learned that the first part of an ester name indicates the alcohol portion and the second indicates the acid portion. The name conforms to how the ester undergoes hydrolysis in base, reacting with base to form an alcohol and a carboxylate anion. Organic and Biological Chemistry SAMPLE EXERCISE 25.6 continued Solve: (a) This ester is derived from ethanol (CH3CH2OH) and benzoic acid (C6 H5COOH). Its name is therefore ethyl benzoate. The net ionic equation for reaction of ethyl benzoate with hydroxide ion is The products are benzoate ion and ethanol. (b) This ester is derived from phenol (C6H5OH) and butanoic acid (commonly called butyric acid) (CH3CH2CH2COOH). The residue from the phenol is called the phenyl group. The ester is therefore named phenyl butyrate. The net ionic equation for the reaction of phenyl butyrate with hydroxide ion is Organic and Biological The products are butyrate ion and phenol. Chemistry SAMPLE EXERCISE 25.6 continued PRACTICE EXERCISE Write the structural formula for the ester formed from propyl alcohol and propionic acid. Answer: Organic and Biological Chemistry  Amides Formed by reaction of carboxylic acids with amines. Organic and Biological Chemistry  Amines Organic bases. Generally have strong, unpleasant odors. Organic and Biological Chemistry  Chirality Carbons with four different groups attached to them are handed, or chiral. Optical isomers or stereoisomers If one stereoisomer is “right-handed,” its enantiomer is “left-handed.” Organic and Biological Chemistry  Chirality S-ibuprofen Many pharmaceuticals are chiral. Often only one enantiomer is clinically active. Organic and Biological Chemistry