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Organic Chemistry The Chemistry of Carbon Intramolecular Forces • Forces of electrostatic attraction within a molecule. • Occur between the nuclei of the atoms and their electrons making up the molecule (i.e. covalent bonds) • Must be broken by chemical means and form new substances when broken. • Determine the chemical properties of a substance. Intermolecular Forces • Forces of attraction between two molecules (i.e. London dispersion forces, dipole–dipole interactions or hydrogen bonds) • Much weaker than Intramolecular forces and are much easier to break. • Physical changes (changes of state) break or weaken these forces. • Do not form new substances when broken. • These forces determine the physical properties of a substance. London Dispersion Forces • These forces are based on the simultaneous attraction of the electrons of one molecule by the positive nuclei of neighbouring molecules • The strength of the force is directly related to the number of electrons and protons in a given molecule • The greater the number of electrons and protons the greater the force Dipole-Dipole Forces • Occur between polar molecules having dipoles. • Molecules with dipoles are characterized by oppositely charged ends that are due to an unequal distribution of charge on the molecule. • The polarity of a molecule is determined by both the polarity of the bond and the shape of the molecule. • These forces are based on the simultaneous attraction of the electrons of one dipole by the dipoles of neighbouring molecules. • The strength of the force is related to the polarity of the given molecule. Hydrogen Bonds • These forces are a type of dipole – dipole interaction. • Occur between Hydrogen atoms in one molecule and highly electronegative atoms (F, O, N) in another. • The strongest of the Intermolecular forces and are about 1/10 the strength of a covalent bond. Characteristics of Organic Compounds 1. Made of carbon atoms in chains or rings. 2. Contain covalent bonds. 3. Principle intermolecular force is London Dispersion. 4. One molecular formula can represent many different compounds (isomers). 5. Properties are determined by the presence of certain groups within the compound (functional groups). Why are there so many Organic Compounds? 1. Carbon has 4 valence electrons therefore 4 bonds. 2. Carbon readily bonds with other carbon atoms forming chains, branched or cyclic compounds. 3. Carbon also readily bonds with other elements such as O, N, S, halogens. General Naming Rules for Organics • The prefix indicates the number of carbon atoms in the chain. • The ending indicates the functional groups in the structure. C=C “ene” -OH “ol # of C’s 1 2 prefix meth eth 3 4 5 6 prop but pent hex 7 8 9 hept oct non 10 dec Alkanes • • All C-C single bonds General Formula CnH2n+2, where “n” is the number of carbon atoms in the chain. Naming 1. Use the correct prefix to indicate the number of carbons. 2. Ending is “ane” Drawing Organic Compounds There are 3 ways to draw an organic compound. 1. Structural Diagram: shows all bonds in the molecule. (the H’s are generally left off to keep structures clean) 2. Condensed Structure: no bonds but all atoms are shown in sequence. (Must put bonds between C’s in for cyclo’s) 3. Line (Skeletal) Diagram: carbon atoms are implied by the vertices (including ends) in the structure, H’s are not shown but any other atoms are written. Structural Condensed butane CH3CH2CH2CH3 or CH3(CH2)2CH3 propan-1-ol CH3CH2CH2OH or HOCH2CH2CH3 methoxyethane CH3OCH2CH3 Line Naming Branched Hydrocarbons 1. 2. 3. 4. 5. 6. Identify the longest continuous chain or ring of carbon atoms. Number the carbons from the end that gives the lowest sum for the numbers of the branches. Name each branch and indicate its location with a number. List the branches in alpha order before the prefix for the number of carbons. Commas separate numbers and hyphens separate numbers from words. If there is more than 1 of the same branch Greek prefixes are used to indicate this but the prefix is not counted in determining alpha order. Common Branches -Br -Cl -F -I -CH3 -CH2CH3 -OH bromo chloro fluoro iodo methyl ethyl hydroxy H3C CH isopropyl H3C H3C H3C tert-butyl C CH3 -NH2 -NO2 amino nitro Alkenes • Contain 1 or more C=C double bond. • When naming use the suffix “ene”. • The position of the double bond is indicated for simple alkenes with 4 or more carbons or for all branched alkenes. • The position of the double bond is indicated with a number in front of the “ene” Alkynes • Contain at least 1 C≡C bond. • When naming use the suffix “yne”. • The position of the triple bond is indicated for simple alkynes with 4 or more carbons or for all branched alkynes. • The position of the triple bond is indicated with a number in front of the “yne” Types of Isomers • • 1. 2. 3. 4. Isomers are molecules with the same formula but different structures. There are different types of isomers Structural: are in the same organic family (i.e. 2 alkenes) but have a different arrangement of the atoms. Functional: same formula but are in different organic families (i.e. an alcohol and ether) Geometric: differ in the placement of groups around a double bond. (“cis-trans” isomers) Optical: mirror images of each other that cannot be superimposed onto each other. Geometric Isomers (“cis-trans”) • Double bonds prevent the rotation of atoms around the bond axis which creates 2 different molecules. • In the “cis” form of the molecule the groups attached to the double bond are on the same side of the double bond. • In the “trans” form of the molecule the groups are attached on different sides of the double bond. • Cis and trans goes with the bond NOT THE GROUPS ATTACHED!! General Rules for Naming Organic Compounds • the prefix indicates the number of carbon atoms. • the ending indicates the functional groups in the structure (C=C “ene”, –OH “ol”). • any branches are indicated before the prefix for the number of carbons in alphabetical order. • below shows the order of different components in the name BRANCHES # of C’s BONDS FUNCTIONAL GROUPS in alpha order alpha alpha order (“oic acid” always last) Naming Cyclo’s 1. Find the longest continuous ring. 2. Add “cyclo” in front of the prefix for the number of carbons. i.e. “cyclopent” 3. Number the ring to give you the lowest sum of all the numbers. You can start anywhere and go clockwise or counter clockwise. 4. If there is only 1 thing on the ring, NO NUMBER is used. (e.g. methylcyclopentane not 1methylcyclopentane) • • • • Naming Hydrocarbon (Alkyl) Branches Not all alkyl branches will be attached to the main chain at carbon 1. When carbon 1 of the branch is attached to the main chain the branch is named using the prefix for the # of C’s with “yl” attached. (i.e. propyl, pentyl) When it is not attached at carbon 1, you must indicate which carbon it is attached at as follows propan-2-yl, pentan-3-yl Aromatics • the organic family which are derivatives of benzene • Benzene has the molecular formula C6H6 • The structural formula of benzene consists of a 6member carbon ring with 3 C=C double bonds. H C H H C C C C C H H H The Structure of Benzene • Benzene is a planar molecule • The carbon-carbon bonds in benzene are all the same length and energy which is evidence that the bonds are not true double and single bonds If the bonds are not true single and double bonds what are they? • The carbon-carbon bonds in benzene are all 139 pm which is intermediate between the length of a C-C single bond and a C=C double bond (double bonds are shorter). • This indicates that the electrons that make up the “double bonds” in benzene are actually delocalized (i.e. shared) around all six carbon atoms. • This arrangement of the electrons is indicated in the LINE DIAGRAM by placing a circle in the centre of the 6-member ring. • Alternatively, benzene can be represented as below. Naming Aromatics Using benzene as the main chain. 1. Identify the groups attached and number accordingly 2. For compounds with 2 groups attached, the following prefixes may be used instead of the numbers; 1,2 = ortho (o), 1,3 = meta (m) and 1,4 = para (p) Cl Cl Cl Cl Cl ortho-dichlorobenzene meta-dichlorobenzene Cl para-dichlorobenzene • When the benzene ring is not the main chain, phenyl is used to indicate a benzene ring as a branch. Common Names for Aromatics Alcohols • contain the hydroxyl group (-OH) • alcohols can be classified by the position of the OH group 1. Primary • the -OH is at the end of the chain Ex. butan-1-ol CH3CH2CH2CH2OH 2. Secondary • the -OH is attached to a C with one H Ex. butan-2-ol CH3CH(OH)CH2CH3 3. Tertiary • the -OH is attached to a C with no H’s Ex. Methylpropan-2-ol C(CH3)3OH Naming Alcohols 1. Determine the name of the main chain containing the hydroxyl group. 2. Remove the ‘e’ on the end of the main chain and add ‘ol’. 3. Indicate the number to which the -OH is bonded to starting at 3 carbons using the same rules as for a double or triple bond. 4. If there are multiple -OH groups indicate this using the appropriate Greek prefix. Ethers • Contain the R-O-R’ functional group. Naming 1. The longest carbon chain connected to the O is the base name. 2. Add “oxy” to the end of the prefix for the other carbon chain (e.g methoxy, propan-2-oxy). 3. Indicate the position of the ether linkage using a number in front of the “oxy branch”. Peroxides • Contain the R-O-O-R’ functional group. • Very unstable and break down spontaneously to form the ether and oxygen gas. Naming 1. list the “yl” forms of the hydrocarbon chains in alpha order, followed by the word peroxide. Aldehydes and Ketones • Aldehydes and ketones both contain the carbonyl group (C=O). • In aldehydes, the carbonyl group is attached to the end carbon. • In ketones, the carbonyl group is attached to a carbon that is not on the end. • They are considered functional isomers of each other. propanal propanone Naming Aldehydes 1. Take the longest chain containing the carbonyl group, remove the “e” and add “al” as the ending. 2. The C=O is always carbon 1. (unless it is with a carboxylic acid) Naming Ketones 1. Take the longest chain containing the carbonyl group, remove the “e” and add “one” as the ending. 2. If necessary indicate the position of the carbonyl using the lowest numerical coefficient. 3. Any substituents are numbered so the sum is the lowest. Carboxylic Acids • Contain the carboxyl functional group Naming 1. Identify the longest chain containing the carboxyl group, remove the “e” and add “oic” acid. 2. The carboxyl group is always carbon 1. Note: “oic acid” always goes last in the name Esters O • Responsible for tastes and odours. • Contain the ester linkage R C R' O • Made from an alcohol and a carboxylic acid. Naming 1. Use the “yl” form of the alcohol proceeded with the “oate” form of the carboxylic acid. i.e. “alkyl oate” O H3C C O CH2CH3 methylpropanoate O CH3 CH H3C C O 2-propylethanoate (isopropylacetate) CH3 Amines • Contain the amino functional group Types of Amines 1. Primary: Contain 1 carbon chain (2 H’s). 2. Secondary: Contain 2 carbon chains (1 H). 3. Tertiary: Contain 3 carbon chains (no H’s). Naming Amines 1. Determine the longest carbon chain and use it as the base name. 2. List the other alkyl chains on the N in alpha order with “N” in front of each to indicate that they are on the nitrogen and not the main chain. 3. Remove the “e” from the base name and a number to indicate where the amino is attached and then add “amine” NH N N-ethylpentan-2-amine trans-N,N-dimethylhex-3-ene-3-amine HO Cl 5-chloro-N-ethyl-N-methylhexan-2-amine-3-ol N Amides • Contain the amide linkage. O C N R R 1 • Structurally similar to esters • This linkage joins amino acids together to create polypeptides. Naming Amides • The name has 2 parts. Base Name: 1. The prefix for the number of carbons in the chain containing the carbonyl. 2. Add amide to the end. Before: 1. Indicate any groups attached the nitrogen using N in place of a number. O O NH N-ethylhexanamide N N,N-dimethylbenzamide O N Cl trans-N-chloro-N-methylhex-2-enamide Organic Reactions Combustion • All of the organic families will under go combustion. Complete Combustion Organic + O2(g) CO2(g) + H2O (g) Incomplete Combustion Organic + O2(g) CO2(g) + H2O (g) + CO(g) + C(s) Substitution • An atom or group on the chain is replaced by another. (SWITCH!! 1 on 1 off) Families that Participate in Substitution 1. Alkanes • With: halogens • Catalyst: UV light • Products: haloalkane + hydrogen halide 2. Aromatics A) With Halogens catalyst: FeBr3 or AlCl3 products: halobenzene + hydrogen halide B) With Alkyl Halide catalyst: AlCl3 products: alkyl benzene + hydrogen halide C) With Nitric Acid catalyst: sulphuric acid products: nitrobenzene + water 3. Alcohols with: hydrogen halide catalyst: ZnCl2 (Lucas Reagent) products: alkyl halide + water • This reaction is a qualitative test for the different types of alcohols because the rate of the reaction differs greatly for a primary, secondary and tertiary alcohol due to the solubility of the resulting alkyl halides Tertiary Alcohol turns cloudy immediately (the alkyl halide is not soluble in water and precipitates out) Secondary Alcohol turns cloudy after 5 minutes Primary Alcohol takes much longer than 5 minutes to turn cloudy 4. Ethers with: 2 binary acids catalyst: heat (Δ) products: 2 alkyl halides + water 5. Preparing Amines (Ammonia) with: alkyl halide catalyst: none products: amine + hydrogen halide Addition Reactions • Adding groups (or atoms) to the chain by breaking a pi bond. 1. Alkenes A) With Hydrogen catalyst: platinum (Pt) product: alkane B) With Halogens catalyst: CCl4 product: haloalkane (2 halogen atoms) C) With Hydrogen Halide ** catalyst: NA product: haloalkane (1 halogen atom) D) With Water ** catalyst: H2SO4 + 100 °C product: alcohol ** these reactions follow Markovnikov’s Rule where the H gets added to the C in the double bond that started with the most H’s Addition Reactions cont’d 2. Alkynes with: same as alkenes but 2 moles of each to fully saturate the triple bond. 3. Aldehydes and Ketones with: Hydrogen (aka a reduction) catalyst: Pt and 101 MPa product: alcohol aldehyde = primary alcohol ketone = secondary alcohol Elimination • Removal of 2 atoms/groups to form a double bond. 1. Alcohols catalyst: H2SO4 and 100 °C products: alkene + water 2. Alkyl halides with: hydroxide ion product: alkene + water + halide ion Oxidation • • A loss of electrons by the carbon atom. Oxidizing agents will usually result in a colour change. dichromate chromium 3+ (orange) (green) permanganate manganese (IV) oxide (purple) (brown) 1. Alkenes oxidizing agent: KMnO4 OR K2Cr2O7 product: “diol” (each C in the double bond gets an OH group) 2. Alcohols oxidizing agent: KMnO4 OR K2Cr2O7 product: depends on type of alcohol Primary Alcohol = aldehyde carboxylic acid Secondary Alcohol = ketone Tertiary Alcohol = NO REACTION 3. Aldehydes product: carboxylic acid - Since ketones can not be oxidized, oxidation reactions can be used as a qualitative test to distinguish between an aldehyde and ketone. Oxidizing Agents: A) KMnO4: purple to brown in aldehyde, stays purple in ketone. B) K2Cr2O7: orange to green in aldehyde, stays orange in ketone. C) Fehling’s Solution (copper (II) solution): blue to an orangish brown precipitate (i.e. copper metal) in an aldehyde, stays blue in a ketone D) Tollen’s Reagent (Silver ions in ammonia): clear and colourless to a black precipitate with a silver mirrored coating on the glassware in an aldehyde, stays colourless in a ketone. • Known as the silver mirror test. Silver Mirror Videos http://www.youtube.com/watch?v=Uo1zW-JImRk http://www.youtube.com/watch?NR=1&feature=en dscreen&v=hUX_cpFWNso Homework • Questions from package Condensation Reactions • Linking 2 molecules together by removing water. • The “H” for the water comes from 1 molecule and the “OH” comes from another. 1. Alcohols A) with: another alcohol catalyst: H2SO4 + 140 °C products: ether + water B) with: a carboxylic acid catalyst: H2SO4 + heat products: ester + water 2. Amines (1° and 2° only) with: carboxylic acid catalyst: H2SO4 + heat products: amide + water Hydrolysis Reactions • Splitting apart of a molecule by adding water. 1. Esters A) Reversible with: water catalyst: H2SO4 + heat products: alcohol + carboxylic acid B) Irreversible with: water + base products: alcohol + carboxylate ion + metal ion 2. Amides with: water catalyst: H2SO4 + heat products: amine + carboxylic acid Rxn. Questions • • • • • • • P. 26 # 1-2 P. 27 # 9-10 P. 31 # 6 P. 37 # 1-2 P. 39 # 4-6 P. 53 # 1 P. 45 # 3 P. 62 # 5-6 P. 55 # 1-10a) c) P. 72 # 7-9 P. 74 # 30-32,35,37-44,47 P. 121 # 38,63,65,71,72,74,103,108,117 Polymers • Read the following sections • 2.2 pg 116-127 • Make sure you know 1. What is a polymer? 2. What an addition polymer is and how it is formed. 3. What a condensation polymer is and how one is formed. 4. Polymer cross-linking 5. Be able to put monomers together to form a polymer and identify the monomer given the polymer. 6. Pg 120 #13, 15-18, pg 121 353-62, pg 127 #1-6