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Organic Chemistry For Dental Students Dr. Nesma Mamdouh Bayoumy Lecture (1) Spring, 2015 1 An Introduction to Organic Compounds Chapter 1 • Organic chemistry is that branch of chemistry that deals with the structure, properties, and reactions of compounds that contain carbon. • Organic compounds are the compound which contains mainly carbon and hydrogen. 2 Hydrocarbons Saturated Alkanes Unsaturated CnH2n+2 Alkenes Alkynes CnH2n CnH2n-2 IUPAC Nomenclature The Three Basic Parts • The name for any organic molecule consists of three basic parts: Prefixes-Parent-Suffix • Basic Part – Suffixes • Suffixes on the end of the name of an organic molecule tell you what major family the molecule belongs to • The suffix for an alkane is “-ane” • The suffix for an alkene is “-ene” • The suffix for an alkyne is “-yne” • Basic Part – the Parent • The “parent” part of the name tells you how many carbons are in the longest chain “main chain” of the molecule. • Counting to Ten in Organic • • • • • • • • • • 01 = meth 02 = eth 03 = prop 04 = but 05 = pent 06 = hex 07 = hept 08 = oct 09 = non 10 = dec • Parent and suffix… • The parent is named based on the number of carbons • 1 carbon = “meth” • So a one-carbon alkane is called methane CH4 • 2 carbons = “eth” • So a two carbon alkane is called ethane. CH3CH3 Parent and suffix… • 3 carbons = “prop” • So a three carbon alkane is called propane. CH3CH2CH3 • 4 carbons = “but” • So a four carbon alkane is called butane. CH3CH2CH2CH3 • So name the following alkane (shown as both condensed formula and a skeletal structure) Answer? nine carbons + alkane family = NONANE • Prefixes • Prefixes are any substituent attached to the main chain (parent) of the molecule. • Prefixes – the Halides • • • • Chlorine is called “chloro” Fluorine is called “ Fluoro” Bromine is called “bromo” Iodine is called “iodo Putting together a name… • The rules for IUPAC nomenclature include: • Step 1: Find the main chain (Longest chain) • Step 2: Number the main chain • Step 3: Identify all prefixes and their position numbers • Step 4: Write the full name: Prefixes-Parent-Suffix. • Step 5: Add punctuation. o Put commas between numbers (2 5 5 becomes 2,5,5) o Put a hyphen between a number and a letter (2 5 5 trimethylheptane becomes 2,5,5-trimethylheptane) o Successive words are merged into one word (trimethyl heptane becomes trimethylheptane) • Follow the rules… Name the following… Br 4-Bromoheptane Br Cl 3,4-Dibromoheptane 3-ethylhexane 3-Bromo-1-chloro-4-methylhexane 1,1-Dibromo-3-methyloctane • Alkyl Groups • Alkyl groups are named similarly to alkanes. • If you remove a hydrogen atom from one of these you get an alkyl group. • A fragment of methane, CH4, would be CH3- called “methyl” • A fragment of ethane, CH3CH3, would be CH3CH2-, called “ethyl”. Example: 6 H3C 3-ethylhexane 5 4 3 2 1 CH CH2 CH CH CH3 CH3 CH3 CH3 2,3,5-Trimethylhexane IUPAC Systematic Nomenclature - Alkanes • If compound has two or more chains of the same length, parent hydrocarbon is chain with greatest number of substituents. Quiz Draw Some Simple Alkanes: 2-methylpentane 3-ethylhexane Example 1: Write the structural formula for 2-methylpentane • Start from counting the number of carbon atoms in the longest chain - pent counts 5 carbons. • Are there any carbon-carbon double bonds? • No – an tells you there aren't any. • Now draw this carbon skeleton: • Put a methyl group on the number 2 carbon atom: Write the structural formula: 2,3-dimethylbutane. 2,2-dimethylbutane. 3-ethyl-2-methylhexane. 4-bromo-3-methylhexene. H3C H C CH 3 H2 C H2 C CH 3 Propyl Groups • There are two possible three-carbon alkyl groups to form from propane, CH3CH2CH3. • The straight chain version: CH3CH2CH2- which is called “propyl” or “n-propyl” (where n stands for “normal” or straight-chained) • The other possibility is to form the fragment on the central carbon: CH3CHCH3, which is called “isopropyl” Name the following molecule: • There are two options: Option 1 is highlighted in red: • The red one has two branches • Option 2 is highlighted in blue: • The blue one has three branches • • • • • Eight carbons in main chain. Octane. Three alkyl groups attached: 2-methyl 5-propyl 6-methyl • Full name: 2,6-dimethyl-5-propyloctane. Nomenclature of Substituents • The name of the alkyl group followed by the name of the class of compound constitutes the common name for alcohols amines, and alkyl halides: Function Class General Formula Suffix Alcohols OH Ol Aldehydes CHO al Ketones C=O one Ethers -O- ether Esters -COO- oate Carboxylic acids -COOH oic acid Amines NH2 amine For each of the compounds A through G shown below, enter the appropriate IUPAC suffix in the designated answer box. In the second answer box enter a number indicating the number of carbon atoms in the longest chain. Compound OH A O B H O C O D OH O OH Cl E CH 2 O G O CH 3 F IUPAC suffix Chain length Organic Chemistry For Dental Students Dr. Nesma Mamdouh Bayoumy Lecture (2) Spring, 2015 17 Examples: Name the following: 3-methylpentanoic acid but-3-enoic acid 4-bromo-5,6-dimethylheptan-2-amine 4-chloro-5,5-dimethylhex -1-en-3-ol 3-ethyl-2,2,4,5-tetramethylhexane Name the following: Hexa-1,4-diene Pent-3-en-1-yne 3,4-Dipropyl-1,3-hexadien-5-yne Hexa-1,3-dien-5-yne 4-bromo-7-methyl-2-nonene 5-fluoro-7,7-dimethyl-2,4-octadiene Nomenclature of Cycloalkanes • Cycloalkanes generally are shown as skeletal structures: Nomenclature of Cycloalkanes • Ring is the parent hydrocarbon unless the alkyl substituent has more carbons; in that case the substituent becomes the parent hydrocarbon. If only one substituent, no need to give it a number: Examples: cyclobutylhexane 2-chloro-1,3-dimethyl cyclohexane propylcyclopentane 3-isopropylcyclo pent-1-ene 1,1,2-trimethylcyclobutane 3-ethylcyclohept-1-ene The line formula for a cyclic compound is shown below. Give the IUPAC name Suffix Number of ring carbons The IUPAC name : 3-ethyl-5,5-dimethylcyclohept-2-en-1-one The Suffix: ONE The number of carbons: 7 carbons • A line formula for a compound is shown below. • How many carbon atoms are in the root chain? • Give the IUPAC name for this compound? Answer: Number of carbons 5 The IUPAC name: 4-chloro-2-ethyl-3-methylpent-4-enoic acid Give the IUPAC name for the following • 4-isopropyl-1-ethyl-2-propylcyclohexane • 3-ethyl-1,5,5-trimethylcyclohexene • 1-cyclohexylheptan-3-ol • 4-bromo-7-chloro-3-isopropylcyclo hept-1-ene Benzene Derivatives Cl Br Chlorobenzene Bromobenzene NO 2 C 2 H5 nitrobenzene ethylbenzene Br 1-methyl-2-propylbenzene 1-bromo-4-ethyl-2-isopropylbenzene 1,3,5-trimethylbenzene