Exercise: Draw the structure of (R)-1-fluoroethanol 2461

Exercise: Draw the structure of (R)-1-fluoroethanol 2462 H (4) F (1) (2) OH CH 3 (3)

Exercise: Draw the structure of (R)-1-fluoroethanol 2463 H (4) F (1) (2) OH CH 3 (3) CH 3

Exercise: Draw the structure of (R)-1-fluoroethanol 2464 H (4) F (1) (2) OH CH 3 (3) CH 3

2465 CH 3 H3CH3C (R)-1-fluoroethanol(S)-1-fluoroethanol

2466 CH 3 H3CH3C (R)-1-fluoroethanol(S)-1-fluoroethanol

Optical Families: D and L prefixes 2467

Optical Families: D and L prefixes Before the absolute configurations of the optical isomers were established by experiment, the compound glyceraldehyde, CH 2 OHCHOHCHO, the simplest chiral carbohydrate, was assigned in the following way: 2468

Optical Families: D and L prefixes Before the absolute configurations of the optical isomers were established by experiment, the compound glyceraldehyde, CH 2 OHCHOHCHO, the simplest chiral carbohydrate, was assigned in the following way: 2469 H H CH 2 OH D-glyceraldehyde L-glyceraldehyde

The absolute configuration of other chiral compounds could be assigned by carrying out various reaction schemes with the different D and L isomers of glyceraldehyde. It turns out that the D isomer of glyceraldehyde is the (+) isomer (from experiment) and the L isomer of glyceraldehyde is the (–) isomer (from experiment). 2470

The absolute configuration of other chiral compounds could be assigned by carrying out various reaction schemes with the different D and L isomers of glyceraldehyde. It turns out that the D isomer of glyceraldehyde is the (+) isomer (from experiment) and the L isomer of glyceraldehyde is the (–) isomer (from experiment). The (+) isomer rotates the plane of polarized light to the right (dextrorotatory – to the right), the (–) isomer rotates the plane of polarized light to the left (levorotatory – to the left). 2471

The D and L isomers refer to the configuration, and not to the sign of the experimental rotation of the plane of polarized light. It is possible to see combinations like D-(–)-lactic acid: 2472 CH 3 H CH 2 OH H D-(+)-glyceraldehyde D-(–)-lactic acid

The lactic acid from muscle tissue is (+)-lactic acid. 2473

For any pair of enantiomers, one is dextrorotatory, and the other is levorotatory. For molecules with a single chiral center, there is no absolute relationship between R and S and (+) and (-). For some chiral molecules the R isomer is (+) (determined by experiment) and for other chiral molecules the R isomer is (-) (determined by experiment). 2474

For any pair of enantiomers, one is dextrorotatory, and the other is levorotatory. For molecules with a single chiral center, there is no absolute relationship between R and S and (+) and (-). For some chiral molecules the R isomer is (+) (determined by experiment) and for other chiral molecules the R isomer is (-) (determined by experiment). So specifying both bits of information is not being redundant: e.g. (S)-(+)-2-butanol: 2475

For any pair of enantiomers, one is dextrorotatory, and the other is levorotatory. For molecules with a single chiral center, there is no absolute relationship between R and S and (+) and (-). For some chiral molecules the R isomer is (+) (determined by experiment) and for other chiral molecules the R isomer is (-) (determined by experiment). So specifying both bits of information is not being redundant: e.g. (S)-(+)-2-butanol: 2476 CH 3 CH 2 CH 3

A 50:50 mixture of the (+) and (–) isomers of the same compound is called a racemic mixture. There is no rotation of the plane of polarization for a racemic mixture. 2477

Example (two chiral centers): Give the name of the following: 2478 CH 3

Example (two chiral centers): Give the name of the following: 2479 CH 3 increasing priority H C O F Br

Example (two chiral centers): Give the name of the following: 2480 CH 3 increasing priority H C O F Br Priority order Carbon 1: Leads to R

Example (two chiral centers): Give the name of the following: 2481 CH 3 increasing priority H C O F Br Priority order Carbon 1: Leads to R Priority order Carbon 2: Leads to S

Example (two chiral centers): Give the name of the following: 2482 CH 3 increasing priority H C O F Br Priority order Carbon 1: Leads to R Priority order Carbon 2: Leads to S (methyl) (substituted methyl)

Example (two chiral centers): Give the name of the following: 2483 CH 3 increasing priority H C O F Br Priority order Carbon 1: Leads to R Priority order Carbon 2: Leads to S So the name is: (1R,2S)-2-bromo-1,2-difluoro-1-propanol

Polymers 2484

Polymer: (Greek: poly meros many parts) 2485

Polymer: (Greek: poly meros many parts) Very large molecules with molar masses ranging from thousands to millions. 2486

Polymer: (Greek: poly meros many parts) Very large molecules with molar masses ranging from thousands to millions. Applications: clothes, food packaging, appliances with plastic components, etc., etc., …. Plastics are polymers. 2487

Two basic types of polymer: 2488

Two basic types of polymer: 1. Thermoplastics: When heated these soften and flow, when cooled, they harden again. This process can be repeated. 2489

Two basic types of polymer: 1. Thermoplastics: When heated these soften and flow, when cooled, they harden again. This process can be repeated. Examples: polyethylene and polystyrene 2490

Two basic types of polymer: 1. Thermoplastics: When heated these soften and flow, when cooled, they harden again. This process can be repeated. Examples: polyethylene and polystyrene 2. Thermosetting plastics: When first heated they are plastic, but further heating forms a highly cross-linked structure. Cannot be softened by reheating. 2491

Two basic types of polymer: 1. Thermoplastics: When heated these soften and flow, when cooled, they harden again. This process can be repeated. Examples: polyethylene and polystyrene 2. Thermosetting plastics: When first heated they are plastic, but further heating forms a highly cross-linked structure. Cannot be softened by reheating. Example: formica. 2492

Monomers: The small (low molar mass) molecules used to synthesize polymers. 2493

Synthetic Polymers 2494

Synthetic Polymers Two principal reaction types: Addition and condensation. 2495

Synthetic Polymers Two principal reaction types: Addition and condensation. Addition Polymers: Made by monomer units directly joining together. 2496

Synthetic Polymers Two principal reaction types: Addition and condensation. Addition Polymers: Made by monomer units directly joining together. Condensation Polymers: Made by monomer units combining so that a small molecule, usually water, is split out. 2497

Addition Polymers 2498

Addition Polymers The monomer for addition polymers normally contains one or more double bonds. 2499

Addition Polymers The monomer for addition polymers normally contains one or more double bonds. The polymerization reaction is initiated using an organic peroxide. 2500

Addition Polymers The monomer for addition polymers normally contains one or more double bonds. The polymerization reaction is initiated using an organic peroxide. R O O R R O. +. O R 2501

Addition Polymers The monomer for addition polymers normally contains one or more double bonds. The polymerization reaction is initiated using an organic peroxide. R O O R R O. +. O R organic peroxide free radicals 2502

Initiation step: +. OR. 2503

Initiation step: +. OR. 2504

Then 2505

Etcetera: where n would typically range from 1000 to 50,

Different experimental conditions give different polymers. 2507

Different experimental conditions give different polymers. 2508

Different experimental conditions give different polymers

Different experimental conditions give different polymers. + branched polymer chain 2510

Cross linked polymers are formed in the following manner: 2511

Cross linked polymers are formed in the following manner: 2512

Cross linked polymers are formed in the following manner: 2513

Cross linked polymers are formed in the following manner: 2514

Cross linked polymers are formed in the following manner: 2515

2516

2517

cross linked polymer 2518

Polyethylene is the most widely used polymer. 2519

Polyethylene is the most widely used polymer. The long linear chain version is called high density polyethylene (HDPE) (d = 0.97 g/ml). 2520