Chemistry Unit 5 - Organic Chemistry PDF

Chemistry Unit 5 - Organic Chemistry Lesson 1 - Organic Chemistry Chain Ring/Cyclic Catenation - the ability to form long chain or ring/cyclic compounds Molecular Orbitals - two or more overlapping atomic orbitals (the space where the electrons are sharing) Atomic Orbitals S and P Hybridized...

Chemistry Unit 5 - Organic Chemistry Lesson 1 - Organic Chemistry Chain Ring/Cyclic Catenation - the ability to form long chain or ring/cyclic compounds Molecular Orbitals - two or more overlapping atomic orbitals (the space where the electrons are sharing) Atomic Orbitals S and P Hybridized Molecular Orbital S and P A combination between the S and P orbitals Molecular Orbitals ⇓ 3 𝑠𝑝 - 1s + 3p 4 electron pairs ​ σ bond TETRAHEDRAL 2 𝑧 𝑠𝑝 - 1s + 2p unhybridized 𝑝 π 𝑏𝑜𝑛𝑑𝑠 ​ TRIGONAL PLANAR 𝑧 𝑥 𝑠𝑝 - 1s + 1p unhybridized 𝑝 𝑝 ​ 2 π 𝑏𝑜𝑛𝑑𝑠 ​ LINEAR Molecular Formula 𝐶𝐻4 / 𝐶2𝐻5𝑂𝐻 Expanded Formula 𝐶𝐻3𝐶𝐻2𝑂𝐻 (ethanol) Structural Formula *carbon can only make 4 bonds* ← 𝐸𝑡ℎ𝑎𝑛𝑜𝑙 Condensed Structural 𝐶𝐻3 − 𝐶𝐻2 − 𝑂𝐻 Line Diagram Nomenclature of Organic Compounds 𝑃𝑟𝑒𝑓𝑖𝑥 + 𝑅𝑜𝑜𝑡 + 𝑆𝑢𝑓𝑓𝑖𝑥 + 𝐹𝑢𝑛𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝐺𝑃 𝑁𝑎𝑚𝑒 (sometimes) ​ # C Atoms 1C - Meth​ an ( C - C ) single bond​ ​ COOH - oic acid 2C - Eth​ en ( C = C ) at LEAST double bond ​ OH - ol 3C - Prop​ yn ( C ≡ C) at LEAST triple bond​ ​ 4C - But 5C - Pent 6C - Hex 7C - Hept  8C - Oct 9C - Non​ 10C - Dec​ ​ ​ ​ ​ ​ e - hydrocarbon ​ ​ ​ ​ Eth + an + ol Lesson 2 - Homologous Series Homologous series - same family Hydrocarbons: ​ ​ ​ ​ Hydrocarbon derivatives: Alkanes - 𝐶𝑛𝐻2𝑛 + 2​​ ​ ​ ​ alcohols - 𝐶𝑛𝐻2𝑛 + 1𝑂𝐻 Alkenes - 𝐶𝑛𝐻2𝑛​ ​ ​ ​ ​ carboxylic acids - 𝐶𝑛𝐻2𝑛 + 1𝐶𝑂𝑂𝐻 Alkynes - 𝐶𝑛𝐻2𝑛 − 2​​ ​ ​ ​ aldehydes - 𝐶𝑛𝐻2𝑛𝑂 ​ ​ ​ ​ ​ ​ ​ ketones - 𝐶𝑛𝐻2𝑛𝑂 ​ ​ ​ ​ ​ ​ ​ amines - 𝐶𝑛𝐻2𝑛 + 1𝑁𝐻2 When arranged in order of increasing or decreasing molecular mass each member differs from its neighbour by +/- 14 (CH2). 14 = 2 hydrogens (1+1), 1 carbon (12), CH2 Physical properties Depending on the family, the melting and boiling points get larger as the molecule gets larger because the london forces are stronger Hydrocarbon chain tends to be non-polar The larger the compound gets, the slower the reaction is because of steric hindrance. (picture going out a door and there are more people at the door, so it is more difficult to get out and will take longer) No dipole-dipole bonds in hydrocarbons because they are non-polar. Dipole-dipole ​ ​ ​ ​ ⤵ Hydrogen bonding ​ ​ ​ Hydrocarbon derivatives London forces ​ ​ ​ Hydrocarbons Isomerism Organic compounds that have the same empirical and molecular formula but have a different structural formula are called isomers and the phenomenon is called isomerism. Constitutional Isomers (ones with branches) C5 H12 Stereoisomers If it is a double bond, it will either be trans or cis Trans isomer - opposite planes, not a reflection of each other when cut in half Cis isomer - same planes, perfect reflection of each other if cut in half Chiral carbon - carbon thats bonded to four different groups It can rotate in plane polarized light If it rotates to the right its referred to as D (+) If it rotates to the left it is referred to as L (-) Optical isomers are very important in pharmaceuticals They will have different reactions, if you take the wrong drug with the wrong rotation it could kill you. Lesson 3 - Nomenclature and Isomerism CH are not drawn in line diagrams, if it is anything other than CH it will specify Branch name goes first (prefix) Separate numbers from letters with a dash (2 - methyl pentane) Root comes from the longest chain. “yl” always goes at the end of the branch name. The number before tells the part where the branch comes off of With multiple branches you name the branches in alphabetical order Ex. 4-ethyl 2-methyl octane In line diagrams the first line represents CH3 and the rest are CH2 4,5-dimethyl hexanol Hex - longest chain is 6 An - all single bonds Ol - OH Meth - one line Yl - branch Di - two separate branches Order of priority is based on atomic mass or mass of the group C-O Look at the carbon that is bonded directly to the oxygen, that will always be number Carbon 1 COOH is heavier than OH so it would take priority 3,4-Dimethyl hexane 2-ethyl 3-methyl pentanol 4-ethyl 5-methyl hexene Order of priority is based on the atomic number first and then secondly the atomic mass Optical isomers - these use the prefix D (+) or L (-) before naming the rest of the compound Substitution reactions: In these chemical reactions one atom or group is replaced by another atom or group. In organic chemistry these reactions occur with saturated organic compounds. Substitution can take place depending on the agent used which can bring about the types of substitution. Only single bonds Free radical substitution - this reaction is initiated by a free radical Free radical is the agent Electrophilic substitution - an electron rich species replaces an atom or group. Aromatic (resonant structures) Nucleophilic substitution – an electron poor species replaces an atom or group. Addition reactions: This type of chemical reaction occurs when an atom or group is added to a compound. This is normally seen in unsaturated compounds sp2 and sp hybridized orbitals. As with substitution we can have electrophilic addition and nucleophilic addition. ​ Requires a double or triple bond Oxidation – this is the addition of oxygen to an organic compound or the removal of hydrogen Reduction – the removal of oxygen or the addition of hydrogen. Combustion – This is a type of oxidation reaction where a compound is burned in the presence of oxygen to form carbon dioxide, water and heat. In addition, Electrophile is electron poor Nucleophile is electron rich No double bond- No addition, can only exchange Nucleophilic substitution Redox Combustion Dehydration/elimination Condensation Is it saturated vs unsaturated? Saturated Means it has only single bonds Looking at substitution Determine if it's polar or nonpolar? If it is polar then it undergoes nucleophilic substitution (halo alkanes) (alcohols), if not, free radical substitution (alkanes) Unsaturated At least one double or triple bond Is it aromatic? If yes, it is electrophilic substitution, if not determine if it's a hydrocarbon? ​​ If it is a hydrocarbon, it will be electrophilic addition, if not, you are looking at nucleophilic addition ​ Lesson 4 - Alkanes All alkanes are single bonded - they are saturated CnH2n +2 Alkanes are sp3 hybridized and the bond angle is 109.5°. The molecular geometry is tetrahedral. Alkanes are named with their Greek root name first which determines the number of C atoms in that alkane followed by the suffix – ane. The “an” indicates single bonds. Alkanes are generally non-polar molecules, and the intermolecular forces present include London forces. Alkanes have lower melting and boiling points compared to organic compounds of similar mass such as alcohols, alkyl halides and organic acids. They are generally insoluble in polar solvents such as water. FREE RADICAL Radical is a species with unpaired electrons Radicals use a dot ​ ​ ​ ​ ​ ​ Homolytic (no charge involved) Chain reaction Ex. uv Cl2 → 2Clᐧ ( initiation ) Clᐧ + CH4 → CH3ᐧ + HCl ( propagation ) CH3 +Cl2 → CH3Cl +Clᐧ ( repeat ) Eventually termination Only occurs with halogens Incomplete combustion - insufficient oxygen Lesson 5 - Alkenes and Alkynes Alkenes and Alkynes are both unsaturated aliphatic hydrocarbons. They are unsaturated because they have multiple bonds. Alkenes are sp2 hybridized and have a sigma bond and a pi bond Alkynes are sp hybridized and have a sigma bond and 2 pi bonds. Isomers The isomers of alkenes -Structural isomers -Positional isomers – position of the double or triple bond -Geometric isomers – the cis or trans alkene isomer Addition reactions E (enemy) is trans Z is cis Chemical properties The reactions of unsaturated compounds The pi electrons in the pi bonds are responsible for the reactivity of alkenes and alkynes. Unsaturated compounds undergo addition reactions. In the case of alkenes and alkynes electrophilic additions. Electrophilic Addition The reactions of alkenes Hydrogenation (+ H) Hydration (+ H2O) Halogenations (+ X2) Hydrohalogenation (+ HX) X = any halogen Won’t focus much on vicinal diols and cyclopropanes Complete this reaction: CH3CH=CH2+H2 →CH3-CH2-CH3 Markovnikov’s Rule This rule states the halogen or OH group in an addition reaction will be added to the more substituted carbon atom. That is the carbon atom with the least hydrogen atoms bonded to it. Lesson 6 - Aromaticity and Cyclic Compounds All aromatic compounds obey the Huckel rule ​ ​ ​ ​ ​ Benzene 4n+2 electrons (n is for rings) 6 pi electrons in benzene→ ​ Pi electrons are found in a double bond (2 each) Aromatic compounds are stable unsaturated compounds A cyclic compound contains several degrees of unsaturation (double bonds) ​ React different from alkenes due to the resonance structure ​ ​ ​ ​ ​ ​ ​ ​ ​ Positional Isomerism The more stable a compound is, the less reactive it will be Substitution you are replacing an atom or group ​ ​ ​ ​ IMPORTANT FOR NAMING ​ ​ ​ Substituent on: Ortho: c1-c2 or c1-c6 (next to each other) Para: c1-c4 (opposite each other) Meta: c1-c3 or c1-c5 (one space in between) ​ ​ (m,o,p) alphabetical order when naming Ortho para trimethylbenzene ​ ​ ​ Ortho para trinitromethylbenzene Electrophilic Substitution Catalysts will speed up the reaction Replacing one atom (any hydrogen) with another atom or group Benzene derivative - benzene with something on it  ​ Strongly activating- more ortho or para Weakly activating - more meta OH - Electrophile would either go in ortho or para CH3 - Electrophile would go in meta place Cycloalkanes 𝐶𝑛𝐻2𝑛 Cycloalkene = 𝐶𝑛𝐻2𝑛 − 2 Not aromatic, do not follow the huckel rule Always a hydrocarbon ALWAYS USE PREFIX CYCLO With more electrons involved- higher melting and boiling point Lesson 7 - Alkyl Halides Alkyl Halides General formula CnH2n+1x X could be either fluorine, chlorine, bromine, or iodine. Alkyl halides can be classified as either primary, secondary, or tertiary alkyl halides. Methyl halides: only one C, Ch3X Primary: C to which X is bonded has only one C-C bond (1 beta carbon) Secondary: C to which X is bonded has two C-C bonds (2 beta carbons) Tertiary: C to which X is bonded has three C-C bonds (3 beta carbons) Alpha carbon is the carbon directly bonded to the halogen Beta carbon is carbon-carbon Nomenclature Name as haloalkane Always number from the alpha carbon Physical Properties What type of intermolecular forces would alkyl halides experience? Polar Bonds Dipole-Dipole Bonding Is it more than one type of intermolecular force? ??? How do this force or forces influence the physical properties of alkyl halides. Higher melting and boiling point compared to hydrocarbons of the same mass. Chemical Properties Electrophilic only works for aromatic compounds Polar Bonds between carbon and halogen ​ For free radical substitution you need nonpolar so its not substitution Electrophilic would only work for aromatic compounds - like benzene because benzene has a source of pi bonds OH group is a strong base and poor leaving group Halogen is replaced by nucleophile in substitution SN2 Mechanisms -Only for primary alkyl halides + − δ δ C – X SN1 Mechanisms -Tertiary alkyl halides -​ The 3 methyl groups stabilize the formation of the carbon carbon, which is why it tends to form carbon cations -​ 2 steps - first form the carbon cation, second, nucleophile forming a bond -​ Slow step first, second step faster Elimination Reactions ​ E1 mechanism is like the SN1 mechanism likewise the E2 is like SN2 ​ The alkyl halide lose a halogen as a halide ion and hydrogen as an H+ ion on the adjacent carbon atom ​ A pi bond is formed. The product is an alkene. This process is called dehydrohalogenation. B can be any base- NaOH etc. E2 is one step E1 is two steps SN2 is one steps SN1 is two steps Elimination 1.​ Zaitsev’s rule When you have elimination of alkyl halide Less hydrogen atoms attached to it 2.​ Hofmann Elimination Lesson 8 - Alcohols and Ethers Alcohols General Formula- CnH2n+1 OH ​ ​ ​ OH - functional group name (ol) ​ ​ ​ ​ Replace “e” with “ol” C2H5OH - Ethanol Physical Properties Polar bonds Hydroxyl group (OH) ​ -hydrogen bonding in alcohols (this is especially true in alcohols with a small hydrocarbon chain) CO - dipole-dipole forces Hydrocarbon chain - london forces Types of Alcohols Primary alcohols → ​ ​ ​ ​ ​ Secondary Alcohols → ​ ​ ​ Tertiary Alcohols → Nomenclature Prefix + Root + Suffix + Functional Group Name (ol) ​ Dehydration Dehydration is a β elimination reaction in which the elements of OH and H are removed from the α and β carbon atoms respectively Dehydration is typically carried out using H2SO4 and other strong acids, or phosphorus oxychloride (POCl3) in the presence of an amine base. Preparation: 𝐻2𝑆𝑂4 +​ 𝐻2𝑂 180*𝐶 → = Alkene ​ ​ +​ Hydration ​ = Alcohol​ Alkyl Halide +​ Nucleophilic Substitution ​ = Alcohol Leaving Groups OH group (hydroxyls) - poor leaving group (bad houseguest that doesn’t know when it's time to leave) X (halogens) - good leaving group (leave when they are supposed to) − OH is a strong base (don’t leave very easily) − NH3 is a strong base − X is a weak base (leave easily) The stronger the base, the poorer the leaving group. Need a very strong acid for the strong base to leave. Dehydration Mechanism Reactions of Alcohols Removing or replacement of OH group Nucleophilic Substitution Dehydration CO-H reaction: 1.​ 2CH3OH + 2Na→ 2CH3O-Na +H2(g) -alkoxide- 2.​ Ester formation Ethers Nomenclature R-o-R R = Hydrocarbon Chain Name both alkyl groups bonded to the O atom and arrange them alphabetically For symmetrical ethers name the alkyl group and add the prefix “di” (NON IUPAC METHOD)↑ Sec (secondary, two beta carbons) Complex ethers: ​ IUPAC system ​ One alkyl group is named as a hydrocarbon chain, and the other is named as part of a substituent bonded to that chain: ​ Name the simpler alkyl group as an alkoxy substituent by changing the –yl ending of the alkyl group to –oxy. ​ Name the remaining alkyl group as an alkane, with the alkoxy group as a substituent bonded to this chain. CH3 - O - CH2 -CH2 - CH3 -​ Methoxy propane ​ Slightly polar - mostly london forces ​ Ether is a very popular solvent for organic compounds ​ Certain ethers have a flash point - catches fire (must be very careful) ​ Ether is easily absorbed through the skin and poisonous ​ Really good solvents because not very reactive unless with a strong acid Ethers are produced when you have an alcohol reacting with an alkyl halide ​ ​ ​ ​ OH- ​ Alcohol + Alkyl Halide → Ether Alcohols and ethers are both common products of nucleophilic substitution Phenols Have an OH group like alcohols, but they are NOT ALCOHOLS The O in the OH group is bonded to a sp-2 hybridized aromatic carbon atom which makes phenols more acidic than alcohols due to the more acidic H atom in the OH group. If it has a negative charge it will be more reactive Phenols can undergo electrophilic aromatic substitution reactions similar to benzene. OH group is a very strong ring activating group -​ The products tend to be ortho and para directed, because the OH group is a very strong ortho / para directing group. Deactivating groups tend to be meta c1 and c3 positions Other reactions include: Nitration Alkylation Acylation Halogenation Acylation of Phenols Acylation of phenols can take place in 2 ways the first one can occur at the carbon in the para position which is known as C-acylation. For C- acylation the halogen carrier AlCl3is required. The second acylation reaction can take place at the O atom in the OH group of phenol. This is known as O – acylation. For this esterification to take place either acyl chloride or an anhydride is required.