Organic Chemistry is: Organic Chemistry The study of the nonmineral (mineral being CO, CO2, etc.) compounds of carbon. Out of over 10million known compounds, about 9million are carbon compounds and thousands of new ones are reported every year. The variety of organic compounds comes from: a. The stability of chains of carbon atoms (covalently bonded) b. The occurrence of isomers (different arrangements of the same number and types of atoms) c. the variety of functional groups (“add-on” groups of atoms) Originally named “organic” because these molecules were associated with living systems and were considered to contain a “vital force” from God that could not be reproduced in the lab. Recall that from the Lewis dot structure that carbon has four valence electrons and is capable of forming four covalent bonds The first organic molecule synthesized in the lab was Urea, by Friedrich Wöhler in 1828. O || NH4OCN(aq) + heat → H2N-C-NH2 Ammonium cyanate (Inorganic salt) Urea (Organic) The simplest type of organic molecules are known as hydrocarbons. They consist of only carbon and hydrogen. These are broken down into three sub-catagories: Alkanes (ane suffix in the name): containing only single bonds between the carbons. Also known as saturated hydrocarbons because they contain as many hydrogen atoms as possible. Space filling model Alkenes (ene suffix in the name): containing at least one double bond between carbons. Alkynes (yne suffix in the name): containing at least one triple bond between carbons. Perspective diagram Geometry: Tetrahedral Ball and stick model Ways of representing the structure of hydrocarbons 1 If hydrogens are not explicitly shown, it is known as a skeletal structure The name of the hydrocarbon is based on the number of carbons in the chain. Can you identify a general formula for alkanes? Note the different types of formulas and what information they give Question: Name this hydrocarbon and write its molecular and condensed structural formula. Answer: Octane C8H18 CH3CH2CH2CH2CH2CH2CH2CH3 or CH3(CH2)6CH3 Many hydrocarbons have branches (also known as substituents or alkyl groups) coming off of their main “parent chain”. Compounds that have the same molecular formula, but different structures are known as structural isomers. The rules (nomenclature) for naming these types of compounds (branchedchain alkanes) requires a series of steps. 1. Find the longest continuous chain of hydrocarbon (remember that they may bend around corners). This is your parent chain. 2. Number the parent chain beginning from the end closest to the first branch. 3. Identify the alkyl groups and the carbon number on the parent chain they are attached to. 4. List the alkyl groups in alphabetical order and the number where the attachment occurs. (Separate numbers from words with hyphens). 5. Finally, list the parent name. Example: 4-ethyl-2-methylhexane NOT 3-ethyl-5-methylhexane 2 Note that it doesn’t matter if the parent chain “bends” around corners. If there are more than one of the same type of alkyl group, the prefixes di, tri, tetra, etc. must be used. These are not used when alphabetizing. Examples: Name the following molecules H If more than one branch occurs on the same parent carbon, the number must be listed each time with a comma in-between numbers. 3C CH H CH 3C 2 CH H 3 3 CH 3 HC C Answers: Problems: a. n-pentane Draw the following structures: b. 2-methylbutane a) n-butane c. 2,4,5-trimethylhexane b) 4-propyloctane d. 3,3-dimethylpentane CH c) 4-ethyl-2-methylhexane d) 2,2,3,3-tetramethylbutane C-C-C Isopropyl | C-C-C-C Iso is used in alphabetizing but sec and tert are not. sec-butyl | C | C-C | Isobutyl C | C | C-C-C tert-butyl (tertiary) | The line on each substituent indicates where it attaches to the parent chain. 3 Name this structure: H3C H3C H3C H3C H3C H3C CH3 H3C CH3 CH3 H3C CH3 4-tert-butyl-2-methyloctane H3C CH3 H3C CH3 CH3 H3C CH3 CH3 H3C CH3 Name this structure: CH3 CH3 4-ethyl-3-isopropyl-2-methylhexane Cycloalkanes CH3 Sometimes carbon molecules form rings. Single bonded rings are known as cycloalkanes. In naming them: 1. If it is a simple ring without any substituents simply name the compound with the word cyclo in front of it. 2. If substituents exist on the ring structure, number the ring carbons in such a way as to create the smallest number(s) for branch locations: CH3 Example: Name this compound H3C 4 CH3 H3C CH3 CH3 1-ethyl-2-isopropylcyclopentane Example: Name this compound CH3 H3C Draw the structure for: H3C 2-ethyl-1-methyl-4-propylcyclohexane CH3 1-isobutyl-3-methylcyclobutane CH3 CH3 Alkene and alkyne nomenclature: Naming compounds with multiple bonds is similar to alkanes but with a few very important exceptions. H3C 1. The parent chain is the longest continuous chain of carbons containing all the multiple bonds. 2. Begin numbering the parent chain from the end closest to the first multiple bond (if it is the same then go to the next double or triple bond) 3. The name must indicate the quantity and location of the multiple bond(s). CH3 5 Because of the potential continuation of a carbon chain on either side of a double bond, sometimes the prefixes “cis” and “trans” must be used to identify which form is being referred to: Draw the structure for 3,4-dichloro-9-methyltrans-dec-3-ene Example: H H3C C CH3 trans-pent-2-ene (trans-2-pentene) H cis-pent-2-ene (cis-2-pentene) C H H H3C C C CH3 H3C H3C CH3 Cl CH3 H3C Cl CH3 CH3 CH3 CH3 Example: Name this structure. Name this compound: H3C H3C H3C CH3 CH3 CH3 H3C CH2 CH3 4-ethyl-2,3,6-trimethylhept-2-ene 6 3-ethylpenta-1,2-diene Name this structure: H3C CH2 H3C CH2 2-hexylbuta-1,3-diene (aka 3-methylenenon-1-ene) H2C CH3 Draw the structure for: 7-ethyl-4-methylnona-2,5-diyne CH2 H2C CH3 Name this structure: CH3 H3C CH3 H3C CH3 H3C 7 Alkane CnH2n+2 sp3 hybridization (109.5o) tetrahedral 3,4-dimethylcyclopentene Alkene CnH2n sp2 hybridization (120o) trigonal planar Alkyne CnH2n-2 sp hybridization (180o) linear Petroleum Refinery Octane Rating Scale from 0 to 100 that measures the anti-knock (pre-ignition) properties of different types of hydrocarbons used for gasoline. 0 = n-heptane 100 = 2,2,4-trimethylpentane (a.k.a. isooctane) Generally, the more branches a hydrocarbon has, the better its anti-knock properties. The old regular “leaded” gasoline used to contain tetraethyllead (T.E.L) as a means to improve anti-knock properties without having to refine the gasoline as much through catalytic cracking (Chemically breaking long hydrocarbons up and reassembling them as shorter chains with branches). Fractional distillation towers typically range in height from 12 to 30 meters Catalytic converters use chemical catalysts at high temperatures to combust CH3 unburned hydrocarbons. H2C CH2 H3C Pb CH2 CH3 H2C CH3 Common Functional Groups: You should learn to recognize these groups. 8 Identify the functional groups on this molecule: CH2 H OH C H C C H H O H C H C H C H Identify the functional groups on this molecule: H O Identify the functional groups on this molecule: Alcohol Alkene O CH2 Ether H OH C H C C H H O H H C H H C O H C H O H H Ketone H C H H N O H H C C C H C O H C H Identify the functional groups on this molecule: Draw the structures for: a. methylpropylether Carboxylic Acid b. 4-methyl-3-hexanone Ester O c. methyl butanoate C O H C H O H C O H H H C H N H H C H C H Amine 9 Ester Synthesis: Draw the structures for: O a. methylpropylether H3C b. 4-methyl-3-hexanone The ester functional group is associated with many aromas and flavors. They can be synthesized to produce artificial smells and flavors CH3 c. methyl butanoate Esters are formed through a condensation reaction between alcohols and carboxylic acids using a catalyst such as H2SO4. O Alcohol + Carboxylic acid → Water + Ester H3C CH3 CH3 O H3C O CH3 Aromatic Hydrocarbons (containing the benzene ring) Example: O Structure originally determined by August Kekulé (1865) + H3C Hydrocarbon chains that do not contain the benzene ring are known as aliphatic. CH3 HO OH Or Propanol (propyl alcohol) butanoic acid (butyric acid) O H2O + CH3 H3C Structure has delocalized p-orbital electrons O Propylbutanoate (propylbutyrate) Water Note: The water is formed from the H of the carboxylic acid and the OH of the alcohol. In naming the ester, the portion of the hydrocarbon chain that came from the alcohol is listed first in the name. Alkyl-substituted benzenes are sometimes referred to as arenes. If the alkyl group has less than six carbons, it is named as a substituted benzene, otherwise the benzene ring is considered the substituent and is called a phenyl (fen’-nil) group. On a compound such as xylene (see below) the terms ortho, meta and para are used to indicate the relative positions of the methyl group substituents on the benzene ring. CH 3 Some benzene containing compounds have special trivial names. For instance: CH 3 Toluene Phenol Analine CH 3 H 3C CH 3 OH H 3C H 3C NH 2 The point of attachment for these compounds is always considered carbon 1 when numbering the ring. Ortho-Xylene (o-Xylene) (1,2-dimethylbenzene) Meta-Xylene (m-Xylene) (1,3-dimethylbenzene) Para-Xylene (p-Xylene) (1,4-dimethylbenzene) 10 Absorption and conversion of light energy in plants. Organic Molecules: Tylenol: The words acetaminophen and paracetamol both come from the chemical name for the compound, N-acetyl-para-aminophenol (or para-acetyl-amino-phenol): N-acetyl-paraaminophenol and para-acetyl-amino-phenol. Caffeine, C8H9O2N4 C27H45OH Hemoglobin Cis and trans fatty acid molecules C2952H4664N812O832S8Fe4 OH Pseudoephedrine NH CH3 CH3 benz(a)anthracene: Found in charred meat from barbecue grill. Carcinogen. NH Ibuprofen CH3 Methamphetamine CH3 Naphthalene (Moth balls) Antifreeze Organic Reactions Hydrogenation (an addition reaction): Hydrogenation of a C=C bond on a catalyst: (1) The reactants have adsorbed to the catalyst's surface and H2 has dissociated. (2) An H atom binds to one of the C atoms. The other C atom is bound to the surface. (3) The second C atom binds to an H atom. The molecule leaves the surface. 11 Polymers: Oxidation reactions with alcohols: Reactive Dyes: Fiber reactive dye is the most permanent of all dye types. Unlike other dyes, it actually forms a covalent bond with the cellulose or protein molecule. Once the bond is formed, what you have is one molecule, as the dye molecule has become an actual part of the cellulose fiber molecule. 12