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Organic Chemistry LET’S KEEP IT SIMPLE…. FOR NOW For Your Viewing Pleasure… https://www.youtube.com/watch?v=ndOwa5zET8Y&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=LKGStmSxxKQ&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=lFPt6sOBFP0&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=narqglzzC44&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=2Iar8g_nO-o&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=0UHvX8lw_3Y&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=dGXkaxNkxRs&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=jhAFeCBPCRI&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=ERwybUxBbQY&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=EgX55uk-7gs&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=MQYEP2v2Or0&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=MMXsdJhepPE&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=_w7O8Co6xLc&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=wP9llcyN1_g&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=jFslN6JHA2E&list=PL7F9D3AE39F738AF8 https://www.youtube.com/watch?v=ODo0-zLzoAk&list=PL7F9D3AE39F738AF8 Organic vs. Inorganic Historically the terms organic and inorganic were originally applied on the basis of the source of the chemical Organic – products of living organisms Inorganic – material from the non-living environment Modern Definition of Organic Compounds Today, it is a major branch of chemistry that deals with compounds of carbon, called ORGANIC compounds*. *Carbon compounds that are exceptions and considered INORGANIC are compounds like: Oxides carbon monoxide (CO(g) ) and carbon dioxide (CO2(g) ), and Ionic compounds of carbon-based ions, such as carbonate CO32-, cyanide CN-, and carbide ions, SiC (silicon carbide) The major source of carbon compounds is still living or previously living things, such as plants, animals and all types of fossil fuels. Modern Definition of Organic Chemistry Organic compounds are covalent compounds that generally exist as gases, liquids or low-melting solids (weak intermolecular forces) Often nonpolar thus insoluble in water (like-dissolves-like) Organic or Inorganic?? Formula CaCO3(s) C25H52(s) Organic or Inorganic? Inorganic (carbonate ion) Organic Ca2C(s) CCl4(l) CH3COOH(l) Inorganic (carbide ion) Organic Organic CO2(g) KCN(s) C12H22O11(s) Inorganic (oxide) Inorganic (cyanide) Organic The Special Nature of the Carbon Atom Special Four properties of carbon. Carbon can form: strong bonds (4 bonding electrons) Long stable chains with single, double and triple bonds Various geometric structures (chains, branched chains, rings, sheets, tubes, spheres) Determining Lewis Formulas So why do we care about bonding capacity? If we know how many bonding e-’s an atom has, we can predict what structure a molecular compound will have Atom H Number of Number of Bonding capacity valence electrons bonding electrons carbon 4 4 4 nitrogen 5 3 3 oxygen 6 2 2 halogens 7 1 1 hydrogen 1 1 1 I.e. Carbon can form 4 single bonds, 2 double bonds, 1 triple and 1 single, or 1 double and 2 singles Polymers Examples of repeating carbon chains: Isomers Compounds with the same number of each type of atom but different structures (C4H10) We will talk about this in more detail later Importance of Organic Chemistry Building units of all living matter: carbohydrates, proteins, fats All foods are organic compounds Photosynthesis is a reaction that makes carbon a part of our food. Carbon is passed along through food chains and sugar from photosynthesis is modified and combined with other materials. Dead organisms are food for other organisms, or are buried in the earth and converted to fossil fuels like peat, coal and petroleum Petroleum is the source of fuel and starting material for plastics, fabrics and industrial chemicals The carbon cycle is an illustration of the interrelationship of all living things with the environment and with technologies that refine and use fossil fuels We will continually outline the importance of organic compounds in our daily lives Organization of Organic Compounds Organic Compounds Hydrocarbons Hydrocarbon Derivatives Aromatics Aliphatics Alkanes Alkenes Alkynes Representing Organic Molecules – Molecular Formulae Empirical indicate Molecular Formula total number of each atom (eg. C4H10) Expanded Indicated Molecular Formula groupings of atoms (eg. CH3CH2CH2CH(CH3)CH3) Representing Organic Molecules – Structural Formulae Structural Formulae: Expanded – indicate shared pair of electrons with lines Condensed – indicate the number of hydrogen atoms bonded to each carbon atom ( CH3 CH2 CH2 CH3 ) Line – lines represent bonds with each end representing C Four Types of Formulas 1. Molecular Formulas C5H10(g) Not very useful for organic compounds because so many isomers can exist 2. Structural Formulas 3. Condensed Structural Formulas 4. Line Diagrams – end of line segment represents carbon – it is assumed to satisfy each carbon’s octet http://www.youtube.com/watch?v=ndOwa5zET8Y Hydrocarbons Organic compounds which contain only hydrogen and carbon Naming Hydrocarbons PREFIXES – ROOT - SUFFIX 1 - meth- 6 - hex- 2 - eth- 7 - hept- 3 - prop- 8 - oct- 4 - but- 9 - nona- 5 - pent- 10 - dec- Naming Organic Compounds Aliphatic Compounds Contain chains of carbon atoms which form homologous series A homologous series contains a consistent increment of change in molecular structure from one compound in the series to the next Naming Organic Compounds Aliphatic Hydrocarbons – contains only hydrogen and carbon atoms Straight line chains of carbon atoms Alicyclic hydrocarbons have carbon atoms forming a closed ring. Still considered aliphatic Alkanes Alkenes Alkynes Only single CC bonds Double C-C Bond present Triple C-C bond present General formula CnH2n+2 General formula: CnH2n General formula: CnH2n-2 Saturated Unsaturated Unsaturated Aliphatic Hydrocarbons - Alkanes Contain chains of single bonds (CnH2n+2) Named with –ane suffix Saturated – additional atoms can not be added w/o breaking the chain May contain branches (substituent added to parent chain) Naming ALKANES 1. Find the parent chain (the longest continuous chain of carbon atoms). Use the appropriate root and the suffix-ane. Naming ALKANES 1. 2. 3. 4. Find the parent chain. Use the appropriate root and suffix. Number the carbon atoms, starting from the end closest to the branch(es) so that the numbers are the lowest possible Identify any branches and their location number on the parent chain (use the suffix –yl for branches) Write the complete IUPAC name, following the format: (number of location, if necessary) – (branch name) (parent chain) 2-methylheptane Naming ALKANES If more than one of the same branch exist, use a multiplier to show this (di, tri). Remember to include all numbers Draw 2,4,6-trimethylheptane Naming ALKANES If different branches exist, name them in alphabetical order ethyl before methyl (e before m in the alphabet) Naming ALKANES If there is more than one branch of the same type, a locating number is given to each branch and a prefix indicating the number of that type of branch is attached to the name. This numbering prefix does not affect the alphabetical order of the branches Draw the structural formula for 3,4-dimethylhexane Summary of Naming Alkanes 1. Find the parent chain. Use the appropriate root and suffix. 2. Number the parent chain carbon atoms, starting from the end closest to the branch(es) so that the numbers are the lowest possible 3. Identify any branches and their location number on the parent chain (us the suffix –yl for branches) 4. If more than one of the same branch exist, use a multiplier (di, tri) to show this. Remember to include all numbers 5. If different branches exist, name them in alphabetical order 6. Separate numbers from numbers using commas, and numbers from words using dashes (no extra spaces) Don’t forget… Questions will specifically ask about structural, condensed structural or line structural formulas. You must be comfortable drawing any of the three Practice Write the IUPAC name for the following 2,5-dimethyl-4-propyloctane Correct the following names: 4-ethyl-2-methylpentane ACTUALLY 2,4-dimethylhexane ALWAYS LOOK FOR LONGEST CHAIN!! Correct the following name: 4,5-dimethylhexane Actually 2,3-dimethylhexane **Want branch numbers to be as low as possible Try These a. b. 2,5,7-trimethyloctane CYCLOALKANES Based on evidence, chemists believe that organic carbon compounds sometimes take the form of cyclic hydrocarbons: Cycloalkanes: Alkanes that form a closed ring General Formula CnH2n Two less hydrogens are present than in straight chain alkanes because the two ends of the molecule are joined Are these considered saturated?? Yes, because they have only single bonds and the max amount of hydrogen's bonded to the carbons Cyclo-compounds will have a higher boiling point than their straight chain partners (because there is an additional bond present) Naming CYCLOALKANES Cycloalkanes are named by placing the prefix cyclo in front of the alkane name, as in cyclopropane and cyclobutane If branches are present, treat the cycloalkane as the parent chain and identify the branches. Since there is no end at which to start the numbering, use the lowest numbers possible Name the following: 1. 2. 1,2-dimethylcyclopentane ethylcyclohexane **Why don’t we need a number? Structural Isomerism Compound with the same molecular formula but different structures They will have different chemical and physical properties – based on their different structures http://www.youtube.com/watch?v=t3ionh5rtlQ Two Types of Structural Isomers a. Geometric - differ only in the geometry of substituted groups (ie. cis and trans) There is always a new concept to learn that extends what you have already learned. In addition to the structural isomers that you know about, there are cis and trans isomers Two Types of Structural Isomers b. Stereoisomers - molecules of the same molecular structure that differ only in the arrangement of atoms in space (Example: mirror image, hands. wings. shoes ..) Stereoisomers Chemical Connection Stereoisomers often have different biological functions. For example, the form of glucose your body uses for energy is D-glucose. Your body is unable to use L-glucose at all. You could eat all the L-glucose you wanted and not gain weight! Review: Find and name all of the isomers of pentane (C5H12(l)) Aliphatic Hydrocarbons – Alkenes -enes ; contain one or more double bond (CnH2n) unsaturated b/c atoms can be added since multiple bond can be at various locations isomers exist [Note: General formula applies only when there is a single multiple bond per molecule] Aliphatic Hydrocarbons – Alkynes -ynes ; contain one or more triple bond (CnH2n-2) [General formula applies only when there is a single multiple bond/molecule] unsaturated Follow b/c atoms can be added the same naming rules as alkenes Naming Alkenes and Alkynes 1. Find the parent chain. It MUST contain the multiple bond. If the bond is a double, the suffix for the parent chain will be -ene If the bond is a triple, the suffix for the parent chain will be –yne 2. Count carbon atoms so that the multiple bond will be on the lowest possible number. Indicate the number that the multiple bond falls on directly before the suffix 3. Name branches as before Naming Alkenes and Alkynes Draw the following as condensed structural formulas: 4-methylpent-2-yne methylpropene (why don’t we need a number?) Naming Alkenes and Alkynes Name the following: 3-methylbut-1-ene 5-methylhex-2-ene Naming Alkenes and Alkynes It is possible for a molecule to have more than one double bond. These are called alkadienes and have the same general formula as alkynes (CnH2n-2) 4. If this is the case, indicate both numbers where the change the suffix to –diene. a) Draw buta-1,3-diene: b) What is the IUPAC name for the following: buta-1,2-diene double bond is formed, and Cycloalkenes and -ynes The rules for naming cycloalkenes and cycloalkynes are the same as naming cycloalkanes The numbering for the carbon atoms begins with the double bond; the carbons of the double bond are carbons 1 and 2; lowest numbers possible Draw 3-methylcyclohexene as a condensed structural formula Aromatics Originally, organic compounds with an aroma or odour were called aromatic compounds Now, aromatics refer to compounds containing a benzene-ring structure Benzene’s formula is C6H6, which would suggest a highly unsaturated and reactive compound Benzene is actually quite unreactive and is considered more stable than alkenes and alkynes Did You Know?? Benzene is a carcinogen and is found naturally in petroleum – why would this be a problem? What do we know about benzene? Formula is C6H6 (3D link) Unreactive – so no true double or triple bonds Carbon-carbon bonds are the same length and strength Each carbon is bonded to a hydrogen So what does benzene look like?? The three double bonds resonate resulting in an overall bond length somewhere in between a single and a double bond, explaining benzene’s stability We will use this line structural formula to represent benzene in compounds Common Aromatic Compounds Include Aspirin and Vanillin (one of the flavour molecules in vanilla) You will notice many aromatic molecules are often depicted using a condensed structural formula except for the benzene ring, which is shown as a line structural formula. This combination is commonly used by chemists, and we will use this method when drawing aromatics. Benzene as a Branch When benzene is added to a hydrocarbon chain as a substituent molecule it is called phenyl Example: 3-methyl-3,5-diphenylhexane Naming Aromatics 1. If an alkyl branch is attached to a benzene ring, the compound is named as an alkylbenzene. Alternatively, the benzene ring may be considered as a branch of a large molecule: in this case, the benzene ring is called a phenyl branch. Which has a phenyl branch? An alkylbenzene Contains a phenyl branch Naming Aromatics If more than one alkyl branch is attached to a benzene ring, the branches are numbered using the lowest numbers possible, starting with one of the branches. 2. Given the choice between two sets of lowest numbers, choose the set that is in both numerical and alphabetical order 1-ethyl-2,4-dimethylbenzene 3-phenyl-4-propyloctane Practice Naming Aromatics Draw 1,2-dimethylbenzene Are there any isomers of this compound? 1,2dimethylbenzene o-dimethylbenzene 1,3dimethylbenzene m-dimethylbenzene 1,4dimethylbenzene p-dimethylbenzene There is also classical way of naming these isomers. The arrangements are denoted by the prefixe:s ortho (o), meta (m) and para (p). These names are still used in industry so you may encounter them in other references. Practice Naming Aromatics Draw the line structural formula for 1-ethyl-3-methylbenzene Draw the line structural formula for 2-phenylpentane Practice Naming Aromatics Draw 3-phenylpent-2-ene Name the following propylbenzene Why is no number needed? Are the hydrogen’s wrong?? Summary We have now learned about both aliphatic and aromatic hydrocarbons. You will need to be comfortable naming all of the following: Organic Halides Organic compounds where one or more hydrogen has been replaced with halogens (F, Cl, Br, I) Common example: CFC (chlorofluorocarbons) Nomenclature is similar to naming branch chains of hydrocarbons, but the branch name used is based on the halogen used [Classification as 1o, 2o or 3o is based on the C to which the halogen is directly attached] chloro-, fluoro-, bromo-, iodo Involved in addition, substitution and elimination reactions Halides Organic Halide What do you need to know about organic halides? May by polar or nonpolar molecules or may have a relatively nonpolar (hydrocarbon) end and a polar (halide) end (**Remember Electronegativity differences) Have higher boiling points than similar hydrocarbons Have very low solubility in water but higher solubility than similar hydrocarbons Are typically good solvents for organic materials such as fats, oils, waxes, gums, resins or rubber Usually toxic or ecologically damaging (DDTs and PCBs) Practice Draw 1,2-dichloroethane Draw 2,2,5-tribromo-5-methylhexane Practice Name the following: CH2Cl2 1,2-dibromoethene chlorobenzene Alcohols An alcohol is an organic compound that contains the –OH functional group (hydroxyl) General formula is R-OH (R = rest of molecule) Alcohols are classified as primary, secondary or tertiary depending on the number of carbons bonded to the carbon that contains the hydroxyl group [Note: not a hydroxide ion b/c oxygen is covalently bonded to carbon] Common Alcohols Methanol (also called wood alcohol) is extremely toxic, causing death and blindness Ethanol (also known as grain alcohol) is the alcohol found in alcoholic beverages and is used in the production of vinegar Gas line antifreeze, windshield de-icer, windshield washer fluid – all contain methanol Naming Alcohols Locate the longest chain that contains an –OH group attached to one of the carbon atoms. Name the parent alkane Replace the –e at the end of the name of the parent alkane with –ol (i.e. butane becomes butanol) Add a position number before the suffix –ol to indicate the location of the – OH group REMEMBER to number the main chain of the hydrocarbon so that the hydroxyl group has the lowest possible position number propan-1-ol Naming Alcohols If there is more than one –OH group (called polyalcohols), leave the –e in the name of the parent alkane and put the appropriate prefix before the suffix –ol (i.e. diol, triol, tetraol) 5. Name and number any branches on the main chain. Add the names of these branches to the prefix. Draw 2,3-dimethylbutan-2-ol Degrees of Alcohols Primary The R-CH2-OH carbon that the hydroxyl group is attached to is bonded to one other carbon atom Degrees of Alcohols R | Secondary -> R – CH – OH The carbon that the hydroxyl group is attached to is bonded to two other carbon atoms Degrees of Alcohols R | Tertiary R – C – OH | R The carbon that the hydroxyl group is attached to is bonded to three other C atoms Practice Naming Alcohols Draw line structural formulas for: 1. cyclohexanol 2. phenol 3. The three isomers of C5H11OH that are pentanols These are the only two cyclic or aromatic alcohols you will need to know as they get very complicated Carboxylic Acid A carboxyl group is composed of a carbon atom double bonded to an oxygen atom and bonded to a hydroxyl group (-COOH) Note: Because the carboxyl group involves three of the carbon atom’s four bonds, the carboxyl is always at the end of a carbon chain or branch Examples: Naming Carboxylic Acids Name the parent alkane Replace the –e at the end of the name of than parent alkane with –oic acid The carbon atoms of the carboxyl group is always given position number 1. Name and number the branches that are attached to the compound. Draw 3-methylbutanoic acid Remember COOH or HOOC can also represent the carboxyl group Naming Carboxylic Acid Draw trichloroethanoic acid (key ingredient in chemical peels) Draw 3-propyloctanoic acid Esters The reaction between a carboxylic acid and an alcohol produces an ester molecule and a molecule of water This reaction is known as a condensation or esterification reaction The ester functional group –COO– is similar to that of a carboxylic acid, except that the H atom of the carboxyl group has been replaced by a hydrocarbon branch. Esters are responsible for natural and artificial fragrance and flavourings in plants and fruits. Esters The formula for an Ester is: R-COO-R’ R= carboxylic acid R’= alcohol Tend to have higher m.p/b.p than carboxylic acids Esters In naming an ester you have to recognize that an ester has 2 distinct parts. The main part contains the C=O group which comes from the parent acid. The second part is the alkyl group. Naming Esters Identify the main part of the ester, which contains the C=O group. This part comes from the parent acid. Begin by naming the parent acid but replace the –oic acid ending of the name with – oate. (propanoic acid becomes propanoate) The second part is the alkyl group that is attached to the single oxygen atom. Name this as you would any other alkyl group (in this case = methyl) Put the names together. Note that esters are named as two words. Naming Esters Name the following ester and the acid and alcohol from which it can be prepared. A strong acid catalyst, such as H2SO4(aq) is used along with some heating to increase the rate of the organic reaction Tip: The branch attached to the oxygen (of the –COO) comes first in the name, the chain attached to the carbon (of the –COO) comes second The Structure and Odour of Some Esters Ester Name Structure Odour Methyl acetate Glue Ethyl acetate Nail Polish Remover Propyl ethanoate Pear Pentyl pentanoate Apple ORGANIC Unit Review Organic or Inorganic?? Formula CaCO3(s) C25H52(s) Organic or Inorganic? Inorganic (carbonate ion) Organic Ca2C(s) CCl4(l) CH3COOH(l) CO2(g) Inorganic (carbide ion) Organic Organic Inorganic (oxide) KCN(s) C12H22O11(s) Inorganic (cyanide) Organic Four Types of Formulas 1. Molecular Formulas 2. Structural Formulas 1. Condensed Structural Formulas 2. Line Diagrams – end of line segment represents carbon organic so many C5H10(g) Not very useful for compounds because isomers can exist – it is assumed to satisfy each carbon’s octet Naming Organic Compounds Aliphatic Hydrocarbons – contains only hydrogen and carbon atoms Straight line chains of carbon atoms Alicyclic hydrocarbons have carbon atoms forming a closed ring. Still considered aliphatic Alkanes Alkenes Alkynes Only single C-C bonds Double C-C Bond present Triple C-C bond present General formula CnH2n+2 General formula: CnH2n General formula: CnH2n-2 Saturated Unsaturated Unsaturated Summary of Naming Alkanes 1. Find the parent chain. Use the appropriate root and suffix. 2. Number the parent chain carbon atoms, starting from the end closest to the branch(es) so that the numbers are the lowest possible 3. Identify any branches and their location number on the parent chain (us the suffix –yl for branches) 4. If more than one of the same branch exist, use a multiplier (di, tri) to show this. Remember to include all numbers 5. If different branches exist, name them in alphabetical order 6. Separate numbers from numbers using commas, and numbers from words using dashes (no extra spaces) CYCLOALKANES Based on evidence, chemists believe that organic carbon compounds sometimes take the form of cyclic hydrocarbons: Cycloalkanes: Alkanes that form a closed ring General Formula CnH2n Two less hydrogens are present than in straight chain alkanes because the two ends of the molecule are joined Are these considered saturated?? Yes, because they have only single bonds and the max amount of hydrogen's bonded to the carbons Cyclo-compounds will have a higher boiling point than their straight chain partners (because there is an additional bond present) Naming Alkenes and Alkynes 1. Find the parent chain. It MUST contain the multiple bond. If the bond is a double, the suffix for the parent chain will be -ene If the bond is a triple, the suffix for the parent chain will be –yne 2. Count carbon atoms so that the multiple bond will be on the lowest possible number. Indicate the number that the multiple bond falls on directly before the suffix 3. Name branches as before Naming Alkenes and Alkynes 4. It is possible for a molecule to have more than one double bond. These are called alkadienes and have the same general formula as alkynes (CnH2n-2) If this is the case, indicate both numbers where the and change the suffix to –diene. a) Draw buta-1,3-diene: b) What is the IUPAC name for the following: buta-1,2-diene double bond is formed, Structural Isomerism Compound with the same molecular formula but different structures They will have different chemical and physical properties – based on their different structures What do we know about benzene? Formula is C6H6 (3D link) Unreactive – so no true double or triple bonds Carbon-carbon bonds are the same length and strength Each carbon is bonded to a hydrogen So what does benzene look like?? The three double bonds resonate resulting in an overall bond length somewhere in between a single and a double bond, explaining benzene’s stability We will use this line structural formula to represent benzene in compounds Practice Naming Aromatics Draw the line structural formula for 1-ethyl-3-methylbenzene Draw the line structural formula for 2-phenylpentane Practice Naming Organic Halides Name the following: CH2Cl2 dichloromethane 1,2-dibromoethene Bonus: Try 1,2-dibromo-1,2-dichloroethene chlorobenzene Alcohols An alcohol is an organic compound that contains the – OH functional group (hydroxyl) General formula is R-OH (R = rest of molecule) Alcohols are classified as primary, secondary or tertiary depending on the number of carbons bonded to the carbon that contains the hydroxyl group Naming Alcohols 1. Locate the longest chain that contains an –OH group attached to one of the carbon atoms. Name the parent alkane 2. Replace the –e at the end of the name of the parent alkane with –ol (i.e. butane becomes butanol) 3. Add a position number before the suffix –ol to indicate the location of the –OH group REMEMBER to number the main chain of the hydrocarbon so that the hydroxyl group has the lowest possible position number propan-1-ol Naming Alcohols If there is more than one –OH group (called polyalcohols), leave the –e in the name of the parent alkane and put the appropriate prefix before the suffix –ol (i.e. diol, triol, tetraol) 4. 5. Name and number any branches on the main chain. Add the names of these branches to the prefix. Draw 2,3-dimethylbutan-2-ol Carboxylic Acids A carboxyl group is composed of a carbon atom double bonded to an oxygen atom and bonded to a hydroxyl group (-COOH) Note: Because the carboxyl group involves three of the carbon atom’s four bonds, the carboxyl is always at the end of a carbon chain or branch Examples: methanoic acid ethanoic acid Carboxylic acids are weak organic acids Naming Carboxylic Acids 1. Name the parent alkane 2. Replace the –e at the end of the name of than parent alkane with –oic acid 3. The carbon atoms of the carboxyl group is always given position number 1. Name and number the branches that are attached to the compound. Draw 3-methylbutanoic acid Remember COOH or HOOC can also represent the carboxyl group HOOC Esters The reaction between a carboxylic acid and an alcohol produces an ester molecule and a molecule of water This reaction is known as a condensation or esterification reaction The ester functional group –COO– is similar to that of a carboxylic acid, except that the H atom of the carboxyl group has been replaced by a hydrocarbon branch. Esters are responsible for natural and artificial fragrance and flavourings in plants and fruits. Naming Esters Name the following ester and the acid and alcohol from which it can be prepared. butanoic acid ethyl butanoate ethanol A strong acid catalyst, such as H2SO4(aq) is used along with some heating to increase the rate of the organic reaction water Tip: The branch attached to the oxygen (of the –COO) comes first in the name, the chain attached to the carbon (of the –COO) comes second Sometimes we need to stop and think… http://www.youtube.com/watch?v=r-Yn4b9iClE Physical Properties of Simple Hydrocarbons Alkanes Non-polar molecules Only intermolecular forces are London Force Boiling point and melting point increase with number of carbons All insoluble in water (like dissolves like) – nonpolar and polar don’t mix 1-4Cs = gas, 5-16Cs = liquid 17 and up = solid at SATP Alkenes Non-polar molecules, therefore insoluble in water Boiling points slightly lower than alkanes with the same number of carbons due to less electrons (unsaturated), resulting in lower London Forces Alkynes Non-polar molecules, therefore insoluble in water Higher boiling points than alkanes and alkenes with similar C #s Accepted explanation: Linear structure around triple bond allows electrons to come closer together than in alkanes/enes, resulting in greater London Force Branching The more branching, the less significant the London Force (~lower b.p.) - more surface area in straight chain hydrocarbons allows more separation of charge, resulting in greater London Force - see Table #3 pg. 378 (i.e. pentane (with 5Cs) has a b.p. of 36oC which is much higher than dimethylpropane (5Cs) -12oC) = because branching decreased the strength of the London force Physical Properties of Hydrocarbon Derivatives Alcohols Much higher boiling points than hydrocarbons (1-12Cs are liquids at SATP) due to hydrogen bonding between hydroxyl groups of adjacent molecules Small alcohols are totally miscible in water, but the larger the hydrocarbon part of the alcohol (nonpolar part), the more nonpolar the alcohol is Carboxylic Acids Like alcohols they have hydrogen bonding, but is more significant due to the C=O. This means greater bps and solubility than alcohols with same number of Cs. Carboxylic acids with 1-4Cs are completely miscible in water Esters Compound Boiling Point (oC) butane -0.5 butan-1-ol 117.2 butanoic acid 165.5 Fruity odour in some cases Polar but they lack the –OH bond therefore do not have hydrogen bonding, so lower bps than both alcohols and carboxylic acids Esters with few carbons are polar enough to be soluble in water Application Question Predict the order of increasing boiling points for the following compounds, and give reasons for your answer. butan-1-ol pentane 1-chlorobutane Answer: (Lowest b.p.): pentane, 1-chlorobutane, butan-1-ol Why? All molecules have a similar number of electrons. Pentane has the lowest boiling point, because it is non-polar so will only have London forces between the molecules. 1-chlorobutane is polar so will have dipole-dipole forces as well as London forces. Butan-1-ol has the highest boiling point because its molecules will have all three intermolecular forces, most importantly, hydrogen bonding Sample Question Predict the relative order of boiling points of the following compounds (lowest to highest). Explain your reasoning. butanol but-1-ene cyclobutane butanoic acid butane Lowest -------------------------------------------------------------> Highest but-1-ene butane cyclobutane butanol butanoic acid Reasoning: but-1-ene has lower LF’s for than butane because it is unsaturated, cyclobutane has an additional bond because cyclic, butanol has H-bonding, butanoic acid has stronger H-bonding) Which would be soluble in water? Butanol and butanoic acid – because they are the only polar molecules and like dissolves like! Physical Refining of Fossil Fuels Let’s Consider… http://nbcpolitics.nbcnews.com/_news/2014/01/31/22524683-report-keystone-pipeline-would-haveminimal-environmental-impact http://www.youtube.com/watch?v=Ea14eufiEq8 http://www.youtube.com/watch?v=KZ96Ss47Fv0 http://www.ted.com/talks/garth_lenz_images_of_ beauty_and_devastation.html http://www.theglobeandmail.com/news/newsvideo/video-al-gore-calls-alberta-oil-sands-anopen-sewer/article11732578/ http://www.youtube.com/watch?v=mGAFnKXrTSs http://www.ethicaloil.org/ http://vimeo.com/40781438 http://www.dailymotion.com/video/xiqql0_jamescameron-to-see-oil-sands-for-himself_news http://www.youtube.com/watch?v=mNW_ms35JKE Crude Oil Refining Crude oil is a complex mixture of hundreds of thousands of compounds, all of which have different boiling points We can take advantage of these different b.p.’s and physically separate the different components using heat This process is called fractional distillation or fractionation A fractional distillation tower contains trays positioned at various levels. Heated crude oil enters near the bottom of the tower. The bottom is kept hot, and the temperature gradually decreases toward the top of the tower. As compounds cool to their boiling point, they condense in the cooler trays. The streams of liquid (called fractions) are withdrawn from the tower at various heights along the tower. Electronic Visual A more detailed look… The vaporized components of the crude oil rise and gradually cool. To get from one level to the next, the vapours are forced to bubble through the liquid condensed in each tray. The figure shows the bubble caps used to allow this to happen. If a gas cools to its boiling point, it will condense and be piped out through the draining tube Crude oil is heated in the fractionation tower without air being present to reduce the risk of mixtures starting to burn or explode Q: How does the number of carbon atoms in a hydrocarbon chain affect its boiling point? Smaller molecules have fewer electrons, so weaker London forces compared with larger molecules. The fractions with higher boiling points are found to contain much larger molecules http://www.youtube.com/watch?v=PYMWUz7TC3A http://www.youtube.com/watch?v=Xsqlv4rWnEg Cracking Cracking: large hydrocarbons are broken into smaller fragments Historically, thermal cracking used extremely high temperatures but created large quantities of solid coke. Now, catalytic cracking uses a catalyst to speed up the reaction and produce less residual products like tar, asphalt and coke Example: C17H36(l) C9H20(l) + C8H16(l) + C(s) larger molecules smaller molecules + carbon In 1960, hydrocracking was developed, which combines catalytic cracking and hydrogenation and produces no coke. Example: C17H36(l) + H2(g) C9H20(l) + C8H16(l) larger molecule + hydrogen smaller molecules http://www.youtube.com/watch?v=VofKBcdZtjo Oil Refining The refining of crude oil can be divided into two main categories: 1. Physical Processes Fractional Distillation: see previous slides Solvent Extraction: solvent is added to selectively dissolve and remove an impurity or to separate a useful product from a mixture 2. Chemical Processes Cracking – larger molecules are broken down into smaller ones Reforming – large molecules are formed from smaller ones These chemical processes are needed because fractional distillation does not produce enough of the hydrocarbons that are in demand (i.e. gasoline) and produces too much of the heavier fractions Catalytic Reforming and Alkylation Catalytic Reforming: improves the quality of the gasoline aliphatic molecule aromatic molecule + hydrogen Alkylation: increases the branching; improves the quality of the fuel aliphatic molecule more branched molecule (AKA: isomerization because it converts molecules into a branched isomer) Combustion Reactions Burning of hydrocarbons in the presence of oxygen Complete Combustion: abundant supply of oxygen; products are carbon dioxide, water vapour and heat Example: C3H8(l) + 5O2(g) 3CO2(g) + 4H2O(g) Incomplete Combustion: limited supply of oxygen; products are carbon monoxide, soot (pure carbon) or any combination of carbon dioxide, carbon monoxide and soot in addition to water vapour and heat Example: 2C8H18(l) + 17O2(g) 16CO(g) + 18H2O(g) OR 2C8H18(l) + 9O2(g) 16C(s) + 18H2O(g) ** Assume complete combustion unless specified otherwise Balancing FYI Example: 2C8H18(l) + 17O2(g) 16CO(g) + 18H2O(g) Can also be balanced using a fraction (you need to be comfortable using this method) – divide each number by 2 C8H18(l) + 17/2 O2(g) 8CO(g) + 9H2O(g) Example: 2C8H18(l) + 9O2(g) 16C(s) + 18H2O(g) can also be balanced as … C8H18(l) + 9/2 O2(g) 8C(s) + 9H2O(g) Combustion Reactions Products depend on O2 present: Excess (complete CO2(g) + H2O (g) + E Limited (hypoxic) combustion) CO (g) + H20 (g) + E Very limited (anoxic) C (s) + H20 (g) + E [Note: no useful organic compounds] Greenhouse Gases Carbon dioxide gas, which is produced during the combustion of fossil fuels, is a greenhouse gas. The production of fuel sources and the burning of fossil fuels has had a damaging impact on the environment Hydrocarbon Reactions 1. Addition alkenes and alkynes + H2(g) alkanes (hydrogenation) alkenes and alkynes + HX (or X2) organic halides 2. Substitution alkanes and aromatics + X2 organic halides 3. Elimination alcohols alkenes + water (dehydration) organic halides + OH- alkenes + halide ion + water 4. Esterification (already covered) carboxylic acid + alcohol ester + water Addition Reactions There are four types of addition reactions, each characterized by a reaction with a different type of molecule: 1) Hydrogenation 2) Hydration 3) Addition of Halogens, Hydrogen Halides and Acids 4) Multiple Additions Addition Reactions: reaction of alkenes and alkynes with hydrogen gas, a halogen compound, or a hydrogen halide compound. 1. Addition reactions usually occur in the presence of a catalyst a) Addition with H2(g) (also called hydrogenation) 1. Addition Reactions: reaction of alkenes and alkynes with hydrogen gas, a halogen compound, or a hydrogen halide compound b) Addition of a halogen 1,2-dichloroethane is a useful solvent and is used to produce chloroethene, the monomer used to make PVC. Since addition reactions involving multiple bonds are very rapid, the alkene product 1,2-dibromoethene can easily undergo a second addition step to produce 1,1,2,2-tetrabromomethane. Excess bromine promotes this second step. 1. Addition Reactions: reaction of alkenes and alkynes with hydrogen gas, a halogen compound, or a hydrogen halide compound Addition of an HX (hydrogen halide) molecule c) Show both possible isomers when predicting the products The addition of hydrogen halides (HF, HCl, HBr or HI) to unsaturated compounds can produce structural isomers, since the hydrogen halide molecules can add in different orientations. However, the type of isomers produced are not always equal. For example only a tiny amount of 1-chloropropane is produced compared to 2-chloropropane in the above reaction. Hydrogenation Conversion of unsaturated hydrocarbons to saturated hydrocarbons Hydrogenated fats are used in stick margarine, fast foods, commercial baked goods (donuts, cookies, crackers), processed foods, and fried foods. Trans fatty acids Manufactured fats created during a process called hydrogenation (aimed at stabilizing polyunsaturated oils to prevent them from becoming rancid and to keep them solid at room temperature.) They may be dangerous for the heart and may pose for cancers. a risk Example: Converting ethyne Example Write a structural formula equation for the production of chloroethene (vinyl chloride) from ethyne (acetylene), hydrogen chloride and a HgCl2 catalyst. Markovnikov’s Rule H-atom of the small molecule being added attaches to the carbon involved in the double bond that is bonded to the most H atoms Hydration During this type of addition reaction, water is added to an unsaturated hydrocarbon, resulting in the production of an alcohol. Use structural diagrams to show the hydration of prop-1-ene that results in the production of propan-1-ol Addition of Halogens, Hydrogen Halides and Acids During this type of addition reaction, alkenes and alkynes are reacted with substances such as Fluorine, Chlorine and Hydrochloric acid. Use structural diagrams to show the addition of bromine to but-2-ene during an addition reaction Multiple Additions When there are two or more molecules being added to a hydrocarbon, the maximum number of bonds that can be broken in order to add the atoms in two. Most additions of multiple molecular groups are reactions with aromatics or alkynes Use structural diagrams to show the addition reaction resulting in the production of 1,1,2,2-tetrafluoropropane by adding two molecules of fluorine gas to propyne Practice Addition Reactions For each of the following questions, draw condensed structural diagrams and name all products + bromine 1,2-dibromoethane 1. ethene 2. hydrogen chloride + ethene 3. 3-methylbut-1-yne + excess hydrogen __ chloroethane 2-methylbutane 2. Substitution Reactions – breaking of a C-H bond in an alkane or an aromatic ring and replacing it with another atom or group of atoms Usually occur slowly at room temperature, so light may be necessary as a catalyst Often substitutes a halogen for a hydrogen No change in saturation Propane contains hydrogen atoms bonded to end carbons and the middle carbon atom, so two different products (isomers) are formed, in unequal proportions 2. Substitution Reactions – breaking of a C-H bond in an alkane or an aromatic ring and replacing it with another atom or group of atoms Benzene rings are stable, like alkanes, so they react slowly with halogens, even in the presence of light. Would all three isomers be created equally? As with alkanes, further substitution can occur in benzene rings, until all hydrogen atoms are replaced by halogen atoms (in the presence of excess halogens) NO Practice Substitution Reactions 1. For each of the following questions, draw condensed structural diagrams and name all products propane + fluorine 1-fluoropropane + 2-fluoropropane + hydrogen fluoride H-F F-F 2. ethane + chlorine chloroethane + hydrogen chloride 3. Elimination Reactions – involves eliminating atoms or groups of atoms from adjacent carbon atoms; decreases the level of saturation a) Alkane cracked into an alkene (uses high temperatures) a) Alcohol is reacted with a catalyst to produce an alkene and water (dehydration – removes a water molecule from the alcohol) a) Alkyl halide reacts with a hydroxide ion (OH-) to produce an alkene (dehydrohalogenation – removes a hydrogen and halogen atom) Practice Elimination Reactions Write a structural formula equation for the preparation of but-2-ene from chlorobutane, in the presence of a strong base Write a structural formula equation for the preparation of but-2-ene from butan-2-ol Esterification Reactions aka condensation Reaction between carboxylic acids and alcohols The production of an ester linkage by reacting a carboxylic acid and an alcohol Example Carboxylic acid + alcohol ester + water http://www.youtube.com/watch?v=n1nyHeDusHk Polymerization Polymers are large molecules made of chains of monomers, small molecules that link together. Polymerization is the formation of polymers from these small units Polymers can occur naturally (proteins, carbohydrates) and can be synthesized (nylon, Teflon, polyethylene) They play an integral part in the function of life systems and have revolutionized the way society functions http://www.nbclearn.com/portal/site/learn/chemistry-now/bulletproof-chemistry-kevlar Addition Polymerization Many plastics (synthetic polymers) are made by this process The polymerization process is initiated with a free radical (a species with an unpaired electron). The free radical attacks and breaks the double bond forming a new free radical that attacks another monomer Addition Polymerization always results in one product, the polymer Requires unsaturated hydrocarbon monomers and bond saturation occurs when the polymer is made Common polymers produced by addition polymerization: Things to know about addition polymers… The polymer names end in –ene (i.e. polystyrene, polypropene). Does this mean they have double bonds? No, the double bonds are saturated by adjacent monomers, as the polymer is made. The name refers to the starting monomer (i.e. polyethene is started by the monomer ethene) What properties make Teflon a good product for non-stick materials? Teflon is made up of C-F bonds which are very strong (not C-H bonds). These very strong bonds make the Teflon highly unreactive (non-sticking), it has a high melting point and it has a slippery surface Condensation Polymerization Monomers combine to form a polymer and a biproduct. Each time a bond forms between monomers, small molecules, such as water, ammonia, or HCl are “condensed” out. The polymerization of nylon: • For condensation polymerization to occur, monomers must be bifunctional, meaning they have at least two functional groups. • If they only had one functional group, then only one bond would form. Condensation Polymerization Condensation polymerization also produces natural polymers, called proteins. Amino acids (monomers) polymerize to make peptides (short chains of amino acids) or proteins (long chains of amino acids) Comparison of Addition and Condensation Polymerization Addition Condensation Needs a double or triple bond in the monomer Needs bifunctional monomers (have two functional groups) Produces only one product, the polymer Produces two products: the polymer and the biproduct (water, ammonia or HCl) Polyester When a carboxylic acid reacts with an alcohol in an esterification reaction, a water molecule is eliminated and a single ester molecule is formed. This esterification reaction can be repeated so many esters are joined in a long chain… a polyester This is created using a dicarboxylic acid (an acid with a carboxyl group at each end) and a diol (an alcohol with a hydroxyl group at each end) The ester linkages are formed end to end between alternating acid and alcohol molecules CHEMISTRY 30 ORGANIC REVIEW