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Chemistry B11 Chapter 16,17 & 18 Amines, Aldehydes, Ketones and Carboxylic Acids Amines Amines Amines: • Are derivatives of ammonia NH3. • Contain N attached to one or more alkyl (Aliphatic amine) or aromatic groups (Aromatic amine). -NH2 amino group NH CH22 CH3 CH3-NH2 CH3-NH-CH3 Eth ylb enzene Amines Amines are classified into three groups: depending on the number of carbon groups bonded to nitrogen. CH3—NH2 CH3 CH3—NH Primary 1° Secondary 2° CH3 CH3—N—CH3 Tertiary 3° Naming Amines IUPAC name – 1° amines The same method as we did for alcohols. - Drop the final “-e” of the parent alkane and replace it by “-amine”. - Use a number to locate the amino group (-NH2) on the parent chain. NH2 NH2 NH2 CH3-CH-CH3 NH2 CH3-CH-CH-CH3 2 4 3 1 CH3 CHCH31 2 Cl 3 2-Propanamine Cyclohexanamine 2-propanamine 3-chloro-2-butanamine H2 N 6 5 4 3 2 1 NH2 1,6-Hexan ediamine 1,6-hexanediamine Naming Amines Common name Names of alkyl groups (In alphabetical order) + “amine” CH3—CH2—NH2 ethylamine CH3—NH —CH3 dimethylamine CH3 | CH3—N—CH2—CH3 ethyldimethylamine Aniline (common name) NH CH22 CH3 CH3 CH=CH Aniline Eth ylb enzene NH CH22 CH3 2 1 3 4 Eth ylb enzene NO2 4-Nitroaniline CH3 NH CH22 CH3 CH=CH 2 2 1 Toluen e Styrene CH3 NH CH22 CH3 CH=CH 1 2 3 3 CH3 4 CH3 Eth ylb enzene Toluen Etheylb enzene Styren Cl Toluen e Styrene 3-Methylaniline 4-Chloro-3-methylaniline Naming Amines IUPAC name – 2° and 3° amines – Take the largest group bonded to nitrogen as the parent amine. – Name the smaller group(s) bonded to nitrogen, and show their locations on nitrogen by using the prefix “N”. NHCH3 N-Meth ylan ilin e CH 3 CH NHCH N N 3 CH 3 C N,N -D imethylN,N -D imeth N-Meth ylan ilinaniline e cyclopentan amin e cyclopentan a CH3 CH3-N-CH2-CH3 N,N-Dimethylethanamine Heterocyclic amines When N is one of the atoms of a ring. N H Pyrrolidine CH3 H Pyridine Nicotine Physical properties of Amines 1. They have unpleasant odors (rotting fish like ammonia). 2. They are polar compounds. Difference in electronegativity between N - H (3.0 – 2.1 = 0.9) 3. 1° and 2° amines have hydrogen bonds (N-H). Weaker than alcohols (O-H). 3° amines do not form hydrogen bonds (no H atom). 4. Boiling points: Hydrocarbons< Amines < Alcohols 5. Almost soluble in water (hydrogen bonding). Chemical properties of Amines They are weak bases (like ammonia): react with acids. (to form water-soluble salts) H CH3 N.. H + .. H – .. O–H H CH3 N + H -... . ..O – H H Some amines present in our blood and make it approximately basic (pH = 7.4). Chemical properties of Amines Aliphatic amines are weak bases by comparison with inorganic bases such as NaOH, they are strong bases among organic compounds. Aliphatic amines are stronger bases than aromatic amines. (slightly stronger than NH3) Clas s Aliph atic Ammonia Aromatic pKb Example 3.0 - 4.0 CH3 CH2 NH2 N ame Ethan amin e Stron ger bas e 4.74 8.5 - 9.5 C6 H5 NH2 Anilin e Weaker base Examples Complete each acid-base reaction and name the salt formed. (a) ( CH3 CH2 ) 2 NH + HCl + CH3 COOH (b ) N Examples Complete each acid-base reaction and name the salt formed. Solutions: (a) (CH3 CH2 ) 2 NH + HCl + - (CH3 CH2 ) 2 NH2 Cl D ieth ylammoniu m chloride - + CH3 COOH (b) N CH3 COO N+ H Pyridinium acetate Aldehydes Ketones Carbonyl group O C Aldehydes Ketones Carboxylic acids Esters O CH3 COCH2 CH3+ N aOH Ethyl acetate Sodium hydroxide H h Aldehydes and Ketones O • In an aldehyde, at least one H atom is attached to a carbonyl group. • In a ketone, two carbon groups are attached to a carbonyl group. C Naming Aldehydes Step 1 Select the longest carbon chain that contains the carbonyl group (C=O). Step 2 Number from the end nearest C=O group. Step 3 Change the ending of parent alkane from -e to -al. No number for carbonyl group C=O (it always comes first). Step 4 Give the location and name of each substituent (alphabetical order) as a prefix to the name of the main chain. Naming Aldehydes • Common names for the first two aldehydes use the prefixes “form” (1C) and “acet” (2C) followed by “aldehyde”. O ║ H─C─H methanal (formaldehyde) O ║ CH3─ C ─H ethanal (acetaldehyde) O ║ CH3─CH2─ C ─H propanal O ║ CH3─CH─CH2─ C─H CH3 4 3 2 1 O ║ Cl─CH2─CH2─ C─H 3 2 3-Methylbutanal 1 3-chloropropanal Naming Ketones Step 1 Select the longest carbon chain that contains the carbonyl group (C=O). Step 2 Number from the end nearest C=O group. Step 3 Change the ending of parent alkane from -e to -one. Use the number to show the location of C=O. Step 4 Give the location and name of each substituent (alphabetical order) as a prefix to the name of the main chain. Naming Ketones • In the common name, name the “alkyl groups” alphabetically attached to the carbonyl group and add the word “ketone”. O ║ CH3 ─ C ─CH3 O ║ CH3─C─CH2─CH3 1 propanone (dimethyl ketone) 2 3 4 2-butanone (ethyl methyl ketone) O O O C 2 1 1 O1 22 5 3 2 Cl 4 H + O2 O 1 Benzaldehyde 2-Methylcycloh exanone 2-Methylcycloh exanone 5-Meth yl-3-h exanone O C 2 Benzoic acid 2-Methylcycloh exanone e 2 O O O 3 4 5 6 5-Meth yl-3-h exanone + O2 2 O 1 H OH 3-Chloro Benzaldehyde 2 6 O C Acetone 1 2 3 4 5 1 6 2 5-Meth yl-3-h exanone 2-Methylcycloh exanone 2-Meth O 5 6 O 2 1 H lbutan al al 3 O O 3 1 O2 H 3 1 2 Hexanal H 2-Prop enal (Acrolein) 4 4 2 3 1 2 H 2-Prop enal (Acrolein) H 3-Methylbutan al OH O 4 5 3 4 3 1 1 3 2 1ylp entanal 3-Hydroxy-4-meth 6 4 H 3-Hydroxy-4-meth ylp entanal NH2 3-Amino-4-ethyl-2-h exanone O OH O 5 4 3 H O OH O 5 1 1 H O 3 2 1 ylp entanal 3-Hydroxy-4-meth 6 4 NH2 3-Amino-4-ethyl-2-h exanone 6 4 3 2 1 NH2 3-Amino-4-ethyl-2-h exanone 3-A Physical properties of Aldehydes and Ketones 1. They have strong odors (ketones have pleasant odors). δ- 2. They are polar compounds. C-O δ+ 3.5-2.5 = 1 3. Only dipole-dipole interactions (no hydrogen bonding). 4. Low boiling points compare to amines and alcohols. Higher than hydrocarbons. H 5. Soluble in water (no soluble in nonpolar compounds). δ- Hydrogen bond with water. δ+ δ+ H O Chemical properties of Aldehydes and Ketones 1. Oxidation: only for aldehydes (not for ketones). O O CH3─CH2─CH2─CH2─C─H = = K2Cr2O7 CH3─CH2─CH2─CH2─C─OH H2SO4 Pentanal Pentanoic acid K2Cr2O7: Oxidizing agent Liquid aldehydes are sensetive to oxidation. No oxidizing agent O C 2 H Benzaldehyde O C + O2 2 OH Benzoic acid Chemical properties of Aldehydes and Ketones 2. Reduction: Like reducing the alkene (C = C) to alkane (C – C): – Reduction of an aldehyde gives a primary alcohol (-CH2OH). – Reduction of a ketone gives a secondary alcohol (-CHOH-). = O + H2 Pentanal 1-Pen tan ol = O CH3─C─CH2─CH3 2-butanone CH3─CH2─CH2─CH2─CH2─ OH + H 2 tran si ti o n m etal catal y st OH - CH3─CH2─CH2─CH2─C─ H tran si ti on metal cataly st CH3─CH─CH2─CH3 2-butanol Chemical properties of Aldehydes and Ketones Sodium borohydride: produces hydride ion: H- NaBH4 Reducing agent Reduction mechanism: H :- + C O H C O - H3 O + H C O-H Hydride ion O NaBH4 OH + H3 O O-H H Carboxylic Acids Carboxylic Acids A carboxylic acid contains a carboxyl group, which is a carbonyl group attach to a hydroxyl group. carbonyl group O CH3 — C—OH hydroxyl group or CH3COOH carboxyl group CH3CO2H Naming Carboxylic Acids • In the IUPAC name of carboxylic acids, the “-e” in the name of the longest chain is replaced by “-oic acid”. • The common names use prefixes “form-” and “acet-” for the first two carboxylic acids. H-COOH CH3-COOH methanoic acid ethanoic acid CH3-CH2-COOH formic acid acetic acid propanoic acid CH3-CH2-CH2-COOH butanoic acid Naming Carboxylic Acids – Number the chain beginning with the carbon of the carboxyl group. – Because the carboxyl carbon is understood to be carbon 1, there is no need to give it a number. CH2 – CH3 CH3 1 3 2 1 CH3─CH─CH2─COOH CH3─CH2─CH─COOH 3-Methylbutanoic acid 2-Ethylbutanoic acid OH 5 O 1 OH 5-Hydroxylhexanoic acid H2 N 4 1 COOH 4-Aminobenzoic acid Naming Dicarboxylic Acids – Add the suffix “-dioic acid” to the name of the parent alkane that contains both carboxyl groups; thus, “-ane” becomes “-anedioic acid”. – The numbers of the carboxyl carbons are not indicated because they can be only at the ends of the chain. O HO O 1 2 3 OH HO O 1 OH O Ehanedioic acid O HO 4 O 5 1 OH HO Propanedioic acid O O 1 OH 6 O O Butanedioic acid HO 1 Pentanedioic acid Hexanedioic acid OH Physical properties of Carboxylic Acids 1- The carboxyl group contains three polar covalent bonds; C=O, C-O, and O-H. So they are so polar. 2- Carboxylic acids have higher boiling points than other types of organic compounds (with the same molecular weight) because of hydrogen bonding. Hydrogen bonding between two molecules H3 C dO d+ H O C C O H d+ CH3 O d- 3- They are more soluble in water than alcohols, ethers, aldehydes, and ketones because of stronger hydrogen bonding. 4- Liquid carboxylic acids have sharp and disagreeable odors. 5- They taste sour (exist in pickle, lime, and lemon). Fatty Acids • Long, unbranched chain carboxylic acids and they are found in animal fats, vegetable oils, or phospholipids of biological membranes. COOH Stearic acid (18:0) (mp 70°C) • COOH Oleic acid (18;1) Most have between 12 and 20 carbons in an unbranched chain. (mp 16°C) • In most unsaturated fatty acids, the cis isomer is usually existedacid and(18:2) the COOH Linoleic COOH Stearic acid (18:0) trans isomer is rare. (mp-5°C) (mp 70°C) COOHCOOH Oleic acid (18;1)acid (18:3) Linolenic (mp 16°C) Cis(mp -11°C) • COOH Linoleic acid (18:2) Unsaturated fatty acids have lower melting points than their saturated (mp-5°C) counterparts. COOH Linolenic acid (18:3) Fatty Acids Saturated fatty acids are solids at room temperature. Packed together Maximum London dispersion forces COOH COOH COOH COOH COOH Fatty Acids Unsaturated fatty acids are liquids at room temperature. Can not packed together London dispersion forces COOH COOH Cis COOH COOH COOH Esters In an ester, the H in the carboxyl group is replaced by an alkyl group. O CH3 — C—O —CH3 ester group Soaps • Natural soaps are sodium or potassium salts of fatty acids. • They are prepared from a blend of tallow and coconut oils (triglycerides). CH2 – CH – CH2 OH • Triglycerides are triesters of glycerol. OH OH 1,2,3-Propanetriol (glycerol, glycerin) • the solid fats are melted with steam and the water insoluble triglyceride layer that forms on the top is removed. Soaps • Preparation of soaps begins by boiling the triglycerides with NaOH. The reaction that takes place is called saponification. • Boiling with KOH gives a potassium soap. O O CH2 OH O O CH2 OCR saponific ation + CH2 OH + CH2 OCR+ 3 N aOH O O 3 RCO N a CHOH RCOCH saponific ation + O + + 3 N aOH 3 RCO N a CHOH RCOCH O CH2 OH CH2 OCR CH2 OH 1,2,3-Propanetriol Sodium soaps CH2 OCR A triglyceride 1,2,3-Propanetriol (Glycerol; glycerin) Sodium soaps A triglyceride ( a triester of glycerol) (Glycerol; glycerin) ( a triester of glycerol) n) Soaps Hydrophobic part: nonpolar Hydrophilic part: polar (remains in contact with environment) O + 3 RCO N a Sodium soaps Soaps When soap is mixed with dirt (grease, oil, and …), soap micelles “dissolve” these nonpolar, water-insoluble molecules. Chemical properties of Carboxylic Acids 1- They are weak acids. Substituents of high electronegativity, especially -OH, -Cl, and -NH3+, near the carboxyl group increase the acidity of carboxylic acids. 2- Reaction with bases: They react with NaOH, KOH, NH3, and other strong bases to form watersoluble salts. COOH + NaOH H2 O Ben zoic acid (slightly soluble in w ater) COOH + NH3 Benzoic acid + COO Na + H2 O Sodiu m b enzoate (60 g/100 mL w ater) H2 O - COO NH4 + Ammoniu m b enzoate Chemical properties of Carboxylic Acids 3- Fischer Esterification: - A carboxylic acid reacts with an alcohols to form an ester. - Using an acid catalyst such as concentrated sulfuric acid. O H2 SO4 CH3 C-OH + H-OCH2 CH3 Eth anoic acid Ethanol (Acetic acid) (Ethyl alcohol) O CH3 COCH2 CH3 + H2 O Ethyl ethanoate (Ethyl acetate) The best way to prepare an ester.