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Organic Chemistry CHS Chemistry What is organic chemistry? (You can use your book!) Agenda • Review Acid/Base Equilibrium • Start Organic Chemistry! Organic Compounds • Consist of mainly four elements Carbon Hydrogen Oxygen Nitrogen Organic: molecules that come from “only” living things Naming organic molecules: Why Do We Need a Separate Set of Rules? Examine some typical organic compounds • CH4 Carbon tetrahydride • C2H6 Dicarbon hexahydride Name these using typical covalent rules So? How about these: • C4H10 Tetracarbon decahydride • C5H12 Pentacarbon ??? hydride Isomers Give the formula for the following H H H H H H C C C C H H H H H Different Structure H C H H H H C C C H H H H C4H10 Same name and formula C4H10 Overall Problems • Memorizing too many prefixes for large numbers • Different structures having the same formulas • Keep in mind that thus far we’ve only dealt with TWO different elements! (What if a chemical is the same structure, but has the OH moved from one C to another? It’s not the same molecule anymore!) So what to do? Hydrogens will always surround the carbons regardless of shape H H H H H H C C C C C H H H H H H C5H12 H H C H H H H H C C C C H H H H H H H C H H H H C C C H H H H C H H C5H12 C5H12 Solution Since number of hydrogens are just always surrounding the carbons, why don’t we ignore them? Name the molecule simply based on number AND the arrangement of CARBONS We can always add prefixes or suffixes later for telling where there are “side branches” Organic Nomenclature • There are three parts to a compound name: • Base: This tells how many carbons are in the longest continuous chain. © 2009, Prentice-Hall, Inc. Organic Nomenclature • There are three parts to a compound name: • Base: This tells how many carbons are in the longest continuous chain. • Suffix: This tells what family of compound it is. © 2009, Prentice-Hall, Inc. Organic Nomenclature • There are three parts to a compound name: • Base: This tells how many carbons are in the longest continuous chain. • Suffix: This tells what type of compound it is. • Prefix: This tells what/how many branches are attached to the chain. © 2009, Prentice-Hall, Inc. 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 (a molecule with all single bonds and only C and H) is “-ane” The Base • The “base” part of the name tells you how many carbons are in the main chain of the molecule • The main chain of the molecule is defined for alkanes as being the longest chain in the molecule Base and suffix… • The base is named based on the number of carbons • 1 carbon = “meth” • So a one-carbon alkane is called methane CH4 Base and suffix… • 2 carbons = “eth” • So a two carbon alkane is called ethane. CH3CH3 Base and suffix… • 3 carbons = “prop” • So a three carbon alkane is called propane. CH3CH2CH3 Base and suffix… • 4 carbons = “but” • So a four carbon alkane is called butane. CH3CH2CH2CH3 And now the rest… • 5 carbons = “pent” • 6 carbons = “hex” • 7 carbons = “hept” • 8 carbons = “oct” • 9 carbons = “non” • 10 carbons = “dec” Mnemonic for First Four Prefixes First four prefixes • Meth• Eth• Prop• But- Monkeys Eat Peeled Bananas Did that Really Help? H H C H H H H H C C H H H CH4 Carbon tetrahydride becomes: Methane C 2 H6 Dicarbon hexahydride becomes: Ethane H H H H H H H H H C C C C C C C C H H H H H H H H H C8H18 Octacarbon ???hydride becomes: Octane Branches • Straight-chain alkanes (Just C & H with single bonds) are now easy H H H H H C C C C H C4H10 Butane H H H H But how do we deal with branches? H H C H H H H C C C H H H H C4H10 ???? Bell Ringer Name the bases for carbon chains 1-10 long Rules Part 2: Prefixes • • • • • Identify the longest unbranched chain of carbons Name it as normal Identify the branch Name the branch but give it a “–yl” suffix Put the names of all branches in alphabetical order in front of the name for the longest carbon chain Prefixes • The most common prefixes we have in organic molecules are those little fragments of carbon pieces attached to the main chains. The carbon fragments are called “alkyl groups”. They all end in “-yl” to indicate they are fragments of a bigger molecule. … but there are other types of fragments out there! (to be continued…) Example methyl Branch is one long H Longest unbranched chain of carbons is three long H C H H H H C C C H propane H H H Methyl Propane Practice H H H H H C C C C H Methyl butane H H H H C H H H H H H H H C C C C C H H H H H H C H H C H H Ethyl pentane One More Practice C C C C C C C C C C Methyl Butane It doesn’t matter which way you go! (Provided you correctly pick the longest unbranched chain) Be Careful H H H H H H C C C C C H H H H H H H C C H H H This is your longest uninterrupted chain Methyl Hexane Methyl Hexane A Small Wrinkle H H H H H H C C C C C H H H H Methyl Pentane H Methyl Pentane H H C H H H H H H H H C C C C C H H H H C H H H These are different molecules, though!!! So Now What? • Since two different molecules can’t have the same name, we must differentiate • If we look closely, though, the only difference between them is the position of the methyl group Positioning 2- Methyl Pentane H H H H H H C C C C C H H 3- Methyl Pentane H H H H H H C H H H H C C C C C H H H H H H C H H H H Here the methyl group is on the second carbon from the end Here the methyl group is on the third carbon from the end So… Rules Part 3: Prefixes • • • • • Identify the longest unbranched chain of carbons Name it as normal Identify the branch Name the branch but give it a “–yl” suffix Put the names of all branches in alphabetical order in front of the name for the longest carbon chain • Put the number of the carbon the branch is on (start numbering from the closest end) Practice H H H H H H H H C C C C C C C H H H C H H H 2-methyl heptane H H H H H H H H H H H H H C C C C C C C C H H H H H C H H H H 4-methyl octane H H H H H H H H H C C C C C C H H H H H H C H H H 2-methyl hexane Multiple Branches • So far we’ve only had one branch • What happens when there are multiple branches? • Add a prefix to indicate the number of a particular type of branch Practice 2- methyl H H C H H H H H H H H C C C C C C C H H H C H H H H H heptane H H 2- methyl 2-methyl, 2-methyl heptane Sounds redundant 2,2 dimethyl heptane More Practice H H H H C H H H H H H H C C C C C C C C H H H H H H H 2, 6-dimethyl octane H H C H H H H H H H C C H 3 ethyl-2,4-dimethyl pentane H H H H C C C C C H H H C H H H H C H H H Name the following H H H H H C C H 3 ethyl-2,4-dimethyl pentane H H H H C C C C C H H H C H H H H C H H H Is your arm sore yet? • Are you sick to death of writing all those carbons? • Even worse, are you sick of writing all those Hydrogens? • How about this… Bell Ringer • Draw the complete and then the skeletal structure of 2-methyl-hexane Shorthand notation H H H H H C C C C H H H H H Keep in mind that we have been ignoring the hydrogens for a long time. Our names have been based entirely on the positioning of the carbons. So lets now ignore the hydrogens completely! Is it that easy? H H H H H H H C C C C C C C H H H C H H H H H H H H H H H H C H H H H H H H C C C C C C C C H H H H H H H H C H H H Give the formula for… One More H H H H H C C H Skeletal notation? H H H H H C C C C C C H H H C H H H H C H H H H 3-ethyl 2,4-dimethyl hexane Name? So is that it? • Not even close!! • There are literally millions of different organic compounds. • What else can we do to make things more complicated? Rings • Thus far we have dealt with chains that are straight or branched. • If hydrocarbons are long enough, one end can wrap around and link up with itself! • We call these cyclic hydrocarbons. Cyclic Hydrocarbons • Name the molecule as normal • Add the prefix cyclo- to the front of the name of the longest chain • Start numbering from the most “important” (longest) branch in the ring Cyclic Compounds • Word of caution: don’t double dip… its really easy to double count the carbon (*) that the alkyl group is attached to. • Alkyl groups are only those BEYOND the ring carbons. Thus, this is a propyl group not a butyl group. * 1 3 2 Cyclic Compounds – Multiple Groups • When a ring has multiple groups, the rule for numbering is: “Number around the ring so as to arrive at the lowest possible sum of the position numbers”. • The sum in this molecule is 1 + 3 = 4. 1 3 Cyclic Compounds – Multiple Groups • Lowest possible sum? 4 1 •1+2+4=7 2 Examples Cyclohexane Cyclooctane More Examples Methyl cyclopentane 1,2-dimethyl cyclohexane Try These 1-ethyl 3-methyl cyclobutane 3-methyl 1-propyl cylclohexane Can You Do This? • • • • • • • • • YES! It takes: Memorization Practice Practice Practice Practice And, oh yes… Practice! Multiple Bonds • So far, even with the cyclic structures we have dealt only with single bonds • Carbon can make multiple bonds to another carbon • This changes the name • Why? They’re in a different family! Examine Structures H H H C C H C2H6 Ethane- notice that each carbon has four bonds H H What will happen to the structure if we double bond the two carbons? H H H C C H C2H4 Each carbon still has four bonds BUT now the hydrogens have changed!! Naming molecules with multiple bonds • • • • • Name the molecule as normal Change the suffix of the longest chain name Double bonds = ene (Alkene family) Triple bonds = yne (alkyne family) Use numbering and prefixes for positioning and multiple multiple bonds. So…. H H H H H C C H H C C H H C C H C2H6 C2H4 C2H2 ethane ethene ethyne H H Name the following: H H H H H H H C C C C C C C H H H H H H H H 2-heptene H H C C C C H H H 1-butene H H H H H H C H H H H C C C C C H H H H 3-methyl 1-pentene How about in Shorthand? 2-pentene Notice the two lines means the double bond is there! Practice! 2-methyl propene 2,4-dimethyl 2-pentene 3-ethyl 2,4,4-trimethyl 1-pentene Bell Ringer: Name the following 2-methyl 1,3-butadiene 1,2-dimethyl1,4-cyclohexadiene Triples? 3, 3-dimethyl1-butyne 1,4-cyclohexadiyne Cis and Trans Cis and Trans tell you which way the carbon chain comes off of the double bonds Cis and Trans Cis and Trans tell you which way the carbon chain comes off of the double bonds (use the longest chain) trans-2-butene cis-2-butene trans-3-methyl hex-3-ene cis-3-methyl 3-hexene Functional Groups (Families) • There are many common groups that we can organized or file into different categories. • Then we can name them based on these categories. Functional Groups • Halogens • Alcohols • Ethers • Aldehydes • Ketones • Carboxylic Acids • Esters • Amines • R-F, R-Cl, R-Br, R-I • R-OH • R-O-R • R-COH • R-CO-R • R-COOH • R-COO-R • R-NH2 Halides • Fluorides, Chlorides, Bromides, and Iodides • Simply name the molecule as normal but add the prefix Fluoro, Chloro, Bromo, or Iodo as necessary Halides Cl 2, 3-dichlorohexane Cl I 3, 3-diiodo-1-pentene I Alcohols • R-OH • Name like normal except add an –ol suffix (use a number to denote where the alcohol is) Alcohols OH OH 2-propanol H H H C C OH H H ethanol 1-cyclobutenol Ethers • R-O-R • Name two “R” groups with –yl endings • End name in “ether” Ethers O O Dimethyl ether Ethyl methyl ether Aldehyde • R-COH • This is a carbon to oxygen double bond with a hydrogen at the end. • Name as normal except use a “-al” suffix Aldehydes H H H O H C C C C H butanal H H H H H Cl H O H C C C C C H H H Cl H 3,3-dichloropentanal Ketones • R-CO-R • This is a carbon to oxygen double bond but in the center of a hydrocarbon chain rather than the end • Name as normal but give it a “-one” suffix Ketones H O H propanone H C C C H H H H H H H O H H C C C C C C H H H H H H 2-hexanone Carboxylic Acids • R-COOH or R-CO2H • This is a carbon to oxygn double bond with the same carbon single-bonded to an OH group. • Name as normal except give it the suffix “-anoic acid”. Carboxylic Acids H H H O H C C C C OH butanoic acid H H H O H H HO C C C F H H 3-fluoropropanoic acid Esters • R-COO-R • This is a carbon to oxygen double bond with a carbon to oxygen single bonded to another single bonded carbon • Name by given secondary branch “-yl” suffix and main branch “-anoate” suffix. Esters Secondary Branch Main Branch H H H H O H H C C C C C O C H H H H H H methyl pentanoate Methyl Pentanoate Esters H H O H H H H H C C C O C C C C H H H H H H H H O H H H H H H C O C C C C C C H H Butyl propanoate H H H H H Methyl hexanoate Amines • R-NH2 • Name the “R” group or groups with “-yl” endings • Add the word “amine” Amines H H Methyl amine H C N H H H H H C N C H H H H Dimethyl amine Summary R Cl Halide R OH Alcohol O O R C H Aldehyde R C R Ketone R O R Ether O R C OH Carboxylic Acid O R C O R Ester R NH2 Amine Summary • Alkanes • Alkenes • Alkynes • Halides (halogens) • Alcohols • Ethers • Aldehydes • Ketones • Carboxylic Acids • Esters • Amines = R-X R-OH R-O-R R-COH R-CO-R R-COOH R-COO-R R-NH2 “-ane” “-ene” “-yne” “-(halogenroot)o” “-ol” “-yl ether” “-al” “-one” “-anoic acid” “-yl” “-anoate” “-yl amine” Other common alkyl side chains iso-propyl tert-butyl iso-butyl iso-pentyl sec-butyl sec-pentyl 5-sec-butyl-4-isopropylnonane 6-tert-butyl-3-methyldecane Aromatic Rings: The last family! Benzene becomes the base name Name the rest like normal! Benzene Chlorobenzene 2-chloro-1methylbenzene methylbenzene Benzoic acid Bell Question: What is the general formula for a carboxylic acid? • Homework questions? Please have it out • In class functional group chart lab: table of functional group, name, prefix/suffix, structure, example : must complete on own time (may use on quest tomorrow) • Today: Review for organic naming Ortho, Meta, Para 3-bromo-14-bromo-1- methylbenzene 2-bromo-1methylbenzene methylbenzene Homework: • Finish WS • 24:33, 37, 43, 47, 49