SCH4U Lee 2.8

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OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) Amine (suffix: - amine ) Similar to alcohols, amines may be classified into primary (1º), secondary (2º), and tertiary (3º). Alcohols are streamed by “how many carbons are bonded to the central carbon . ” For amines, it is “how many carbons are bonded to the central nitrogen. Exercise 1. Look at the two amines on the right. Are they primary/secondary/tertiary amines? Primary, secondary Some simple primary amines: Amines are named very much like alcohols, too. (methanol ↔ methanamine; propan-2-ol ↔ propan-2-amine). If you are not sure, simply pretend this -NH 2 is an -OH. For secondary and tertiary amines, the shorter carbon chain attached to the N becomes a side chain (e.g. methyl), though it has be hyphenated with N- (e.g. N-methyl ) in order to stress that the side chain grows on N, not on the carbon main chain. For tertiary amines there are two side chains, each is preceded with N- . The old name of N,N-dimethylmethanamine is trimethylamine. It is released when seafood decomposes, giving it the distinctive fish market smell. 1
OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) Exercise 2 . Which should have a higher boiling point, propan-1-amine or N,N-dimethylmethanamine? Why? The primary amine has one δ - N lone pair and two δ + H, but the tertiary amine has only the N lone pair. Exercise 3 . Let’s practice a bit more naming. Answers are on worksheet bundle page 18. Amines smells bad Many amines give out a rotten smell. You should have been familiar with the smell of ammonia. The two amines on the right (cadaverine and putrescine) are produced when amino acids in proteins are broken down by microbial activities, a sign of a rotting corpse. Our ancestors had a better chance of survival as they stayed away from smelly, pathogen-layden corpses. (Are these primary, secondary, or tertiary amines? IUPAC names?) Chefs can remove the unpleasant fish smell by squeezing lemon juice on the decomposing fish. Sometimes restaurants give the customers another piece of lemon. The carboxylic acid (citric acid) of lemon juice can react with amines through acid-base neutralization: H + + R-NH 2 → R-NH 3 + (ammonium group) H + + R 3 -N → R 3 -NH + The trigonal pyramidal R-NH 2 + lone pair is converted to a tetrahedral R-NH 3 + (still sp 3 ). As a positively charged ion, the -NH 3 + has much stronger intermolecular attractions and does not evaporate. Customers eat all of the decomposed amino acids. (It is fine as long as the fish is cooked enough to kill the pathogens.) Amines are bases Due to their ability to accept H + and therefore neutralize acids, amines behave as bases (Unit 4). In a 1M solution, only about 1 out of 50 methanamine’s -NH 2 exists as its -NH 3 + version. Amines are therefore weak bases. However, it is quite common in the cell to see the -COO - of a carboxyl group forming an intermolecular ionic interaction with the -NH 3 + from the amine group because the physiological pH favours the ionic form (Unit 4). The acid and base properties of carboxylic acid and amine explains why in organic chemistry, negative charge and oxygen are red , while positive charge and nitrogen are blue . Exercise 3 . Amine has no -OH to give away. Why is it a base? Amine can accept H + (e.g. R-NH 2 + H + → R-NH 3 + ) and neutralize the acid (which donates H + ) 2
OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) Exercise 4 . Why does the restaurant serve me a piece of lemon with my fish & chip? The citric acid in lemon can donate H + to bad-smelling amines and turning them into positively-charged ions, which do not evaporate easily - no longer smells bad. Exercise 5. Identify the amines in the compounds below. Is it a primary, secondary, or tertiary amine? How many hydrogen bonds can be made (maximum/average) among themselves? Extended topics: TED-ED: How do drugs affect the brain? https://youtu.be/8qK0hxuXOC8 Mechanism of Drug Addiction in the Brain https://youtu.be/NxHNxmJv2bQ Amides (- amide ) Amides have both nitrogen and oxygen. Amide is named quite like an amine. For example, when an -NH 2 is attached to an ethane, it is ethan amine . When an amide ( C =O and C -NH 2 , on the same carbon ) happens at the end of an ethane, it is ethan amide . Depending on how many C is bonded to the N , the 3
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OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) amide could be primary, secondary, or tertiary, just like amines. Primary (1º) amides: methan amide 2-methyl propan amide (the 2-methyl side chain grows on C main chain) For amines, the shorter carbon chain becomes a N- side chain. For amides, however, the main chain is decided by where the C=O is. The N- side chains do not have the C=O. Exercise 6 . Let’s name some amides! Answers are on worksheet bundle page 19. Condensation reaction to form amide 4
OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) Amides are similar to esters in a number of aspects. First, the atoms are organized similar to esters, with the C =O and C -N-R (same C ). Ester is C =O and C -O-R. The production of amides is also similar to esterification. An amide is produced in a condensation reaction of a carboxylic acid and an amine. Water is also a byproduct. Note that when a 1º amine condenses with carboxylic acid, it becomes a 2º amide, because there is now an extra C-N bond. A 2º amine, for the same reason, produces a 3º amide. A 3º amine cannot be turned into an amide because there is no N-H bond to break. Note that a 1º amide is made when ammonia (essentially a 0º amine, like methanol is 0º alcohol) reacts with carboxylic acid. Exercise 7. Predict the products of the following condensation reactions (or no reaction), both line diagrams and IUPAC names: (a) butanoic acid + ammonia → butanamide + H 2 O (b) ethanoic acid + methan amine N- methyl ethanamide + H 2 O (c) propanoic acid + N-methyl ethan amine → N-ethyl-N-methylpropanamide + H 2 O (d) methanoic acid + N-ethyl-N-methyl propan amine → no reaction (no N-H left to break) 5
OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) (e) hexanamide + H 2 O → ammonia + hexanoic acid (f) N,N-dimethylpropanamide + H 2 O → propanoic acid + N-methylmethanamine Comparing the boiling points of functional groups b.p. formula b.p. formula propane -42°C C 3 H 8 propanoic acid 141ºC C 3 H 6 O 2 propan-1-ol 97°C C 3 H 8 O methyl ethanoate 57ºC C 3 H 6 O 2 methoxyethane 7ºC C 3 H 8 O propan-1-amine 47ºC C 3 H 7 N propanal 49°C C 3 H 6 O propanamide 213ºC C 3 H 7 NO propanone 56°C C 3 H 6 O Exercise 8 . Why does propanamide have a higher boiling point (which is measured with the pure substance) than propanoic acid? # of δ - / # of δ + / # of hydrogen bonds on average Propanoic acid: 4 / 1 / 2 Propanamide: 3 / 2 / 4 Exercise 9 . Identify functional groups! 6
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OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) Extended topic: SciShow: How Weed Works: THC https://youtu.be/FsJzCdFlpyQ A KILLER HIGH: Understanding Fentanyl https://youtu.be/cPZAnMqkrG4 National Geography: This Is What Happens to Your Brain on Opioids https://youtu.be/NDVV_M__CSI TED-ED: What causes opioid addiction, and why is it so tough to combat? https://youtu.be/V0CdS128-q4 End of Quiz #7 coverage 7
OCV Chemistry, Grade 12 University Preparation (SCH4U-04/05) Ottawa-Carleton Virtual Secondary School 2020-2021 Mr. Daniel Cho-En Lee ( daniel.cho-en.lee@ocdsb.ca ) SCH4U-06 Quiz #7, 8 https://docs.google.com/presentation/d/15LdhO1tJ0I8jTRK_lAYDa0esZfd8QuPfWlqazTBHrvc/edit?usp=sharing https://docs.google.com/presentation/d/1ZUfjZAyt6mPt8lFMDSNjYOwk3IbqtXQP6AiQmLo6cyE/edit?usp=sharing 8