An instrument that measures the rotation of light.
A mixture of equal quantities of enantiomers is not active.
Even though the absolute configuration of either molecule may not be known, the relationship between the two configurations is determined by experimentation.
The pure enantiomers are separated from a racemic mixture.
A resolving agent is required for resolution.
A chromatographic column is used to separate enantiomers.
When groups are interchanged, an atom gives rise to stereoisomers.
The most common stereocenters are asymmetric carbon atoms and double-bonded carbons.
Giving rise to stereoisomers.
A stereoisomer is created by the characteristic of an atom or a group of atoms.
The atoms in the same order are different in how they are oriented in space.
When the molecules are placed on top of each other, the three-dimensional positions of all atoms coincide.
Each skill is followed by problem numbers.
Draw all the stereoisomers of the structure.
Draw their mirror images and classify them as achiral or chiral.
Any mirror planes of symmetry can be identified and drawn.
The stereochemistry of compounds with one or more asymmetric carbon atoms can be represented by the use of Fischer projections.
Explain the physical and chemical properties of pairs of enantiomers, diastereomers, and meso compounds.
There are four structures that are active.
The following projections can be converted to perspective formulas.
There are stereochemical relationships between structures.
Same compound, structural isomers, enantiomers, diastereomers are examples.
For each structure, draw the enantiomer.
The following samples were taken at 25 degC.
The sample is dissolved in 20.0 liters of alcohol.
The solution is placed in a tube.
The rotation iscounterclockwise.
0.050 g of sample is dissolved in 2.0 mL of alcohol and placed in a tube.
The rotation is clockwise.
bromine is introduced at the benzylic position next to the aromatic ring by free-radical bromination of the following compound.
Two stereoisomers result if the reaction stops at the monobromination stage.
There is a mechanism to show why free-radical halogenation occurs at the benzylic position.
There are two stereoisomers that result from monobromination at the benzylic position.
Will the two stereoisomers have the same physical properties?
This is a difficult problem if you think you know your definitions.
There are two structures and one pair of enantiomers.
C3 is not asymmetric nor is it a chiral center, yet it is a stereocenter.
Show how C3 is not a stereocenter.
A graduate student was looking at chemistry while studying cyclohexanones.
She was surprised to find that the product she used was active.
She repurified the product to make sure there were no contaminants.
The product was active.
The name implies that it can be degraded to d-(+)-glyceraldehyde.
The name implies that d-(-)-erythrose is active.
The absolute configuration of d-(+)-glyceraldehyde is determined by knowing the absolute configuration of d-(-)-erythrose.
We don't have to imagine all possible diastereomers of the compound in order to apply the working definition.
The working definition is not as complete as the original one.
Name alkyl halides, explain their physical properties, and describe their common uses.
The properties and reactions of alkyl predict which product is a halide.
Two of the most likely ways to introduce substitution and elimination are with alkyl halides.
Stereochemistry will play a major role in the study of these reactions.
Many other reactions show similarities to Halogen-containing organic substitution and elimination, and the techniques introduced in this chapter will be used compounds that are not very common in our study of organic reactions.
There are three major classes of organic compounds that are found in plants and venoms.
When it is ring, there are 2 hybrid carbon atoms of chlorine and bromine.
The chemistry of vinyl halides and aryl halides is different from the chemistry of alkyl disturbed by predatory fishes.
In later chapters, we consider the reactions of vinyl halides and aryl halides.
The structures of some alkyl halides, vinyl halides, and aryl halides are shown here.
The carbon-halogen bond in an alkyl halide is polar because it has more halogen atoms than carbon atoms.
A lot of reactions of alkyl halides result from breaking this bond.
The map shows the EPM of chloromethane around the chlorine atom and around the carbon and hydrogen atoms.
This carbon and Chloromethane can be attacked by a nucleophile.
The bonding pair of electrons with the halogen atom can leave as a halide ion.
By bond is seen in the EPM as an electron serving as a leaving group, the halogen can be eliminated from the alkyl halide, or it can rich region around chlorine and be replaced by a wide variety of functional groups.
The blue region around alkyl halides can be used as intermediates in the synthesis of many other functional groups.
There are two ways of naming alkyl halides.
Appendix 5 contains information about me.
Common names for halomethanes are not related to their structures.
The structures of the compounds should be given.
According to the nature of the carbon atom, butyl bromide Alkyl halides are classified.
Alkyl halides are used as household and industrial solvent.
Chloroform can be converted to dry cleaners using 1,1,1-trichloroethane and other solvents because it is toxic and causes cancer.
The room temperature was dissolved with Methylene chloride.
Coffee beans are used to produce Phosgene.
Concerns about the safety of extremely toxic because it reacts with coffee with residual traces of methylene chloride prompted coffee producers to use and deactivate many biological mol supercritical carbon dioxide instead.
Chloroform is more dangerous than ecules.
A small amount of alcohol has been replaced by methylene chloride in some industrial degreasers and paint removers.
methylene chloride is the safest halogenated solvent.
Alkyl halides are used as starting materials for making more complex molecules.
An important tool for organic synthesis is the conversion of alkyl halides to organometallic reagents.
Section 10-8 discusses the formation of organometallic compounds.
General anesthesia with a patient who is unconscious and relaxed was opened up in the 1840s by chloroform.
Chloroform is toxic and can cause cancer, so it was abandoned in favor of safer anesthetics.
The trade name for a less toxic halogenated anesthetic is Halothane.
Minor procedures can be helped by the use of ethyl chloride.
The numbing effect is enhanced when it is sprayed on the skin.
There are other alkyl halides and haloethers that are less toxic than chloroform, and they are still among the most common anesthetics.
There are some recent ones.
Their structures are compared with another.
People who were working or sleeping near leaking refrigerators were often killed by ammonia.
At one time, freon-12(r) was the most widely used refrigerant.
Earth's protective ozone layer was destroyed by freons released into the atmosphere.
The chlorine atoms in the ozone depletes into oxygen in the air.
The "hole" in the ozone layer that has been detected over the South Pole is blamed on the freon-catalyzed depletion of ozone.
Chapter 4 shows the extent of the ozone hole over the South Pole.
The future production and use of the ozone has been limited because of Halogenated compounds.
Low-boiling breakdown by soilbacteria has replaced freon-12 in aerosol cans.
Many of them are carbon dioxide or hydrocarbons.
The insoluble and unreactive elements in Freon-12 have been replaced by CHClF water.
There are some strains of the stratosphere.
HCFC-123 is used as a substitute for freon-11 in making plastic foams.
They use freon-134a as their source of food.
Human health has been contributed to by the use of alkyl halides.
People have died from diseases caused by mosquitoes, fleas, and other vermin.
The bubonic plague wiped out a third of the population of Europe in the Middle Ages.
People could not survive mosquito-borne diseases such as malaria, yellow fever, and sleeping sickness in the entire regions of Africa and tropical America.
These compounds are just as bad for birds, animals, and people as they are for insects.
Their use is hazardous, but still preferable to death by disease or starvation.
The war against insects changed in 1939 after the discovery of DDT.
An ounce of DDT is required to kill a person, but the same amount of pesticides protects an acre of land.
The mosquitoes and tsetse flies are carrying diseases.
Many inventions show side effects.
It is a long-term structure of the drug.
There are pesticides in the environment.
Decreases in several species are caused by centrations in wildlife.
In 1972, ethane was banned.
It was the first pesticide that was chlorinated.
Its use was large by the U.S. Environmental Protection Agency.
Pesticides accumulate in the environment and are rarely used.
Lindane is used to control body lice.
Many other pesticides have been developed.
Toxic effects are produced in wildlife when they accumulate in the environment.
If they are applied correctly, others can be used.
Chlorinated pesticides are rarely used in agriculture.
They are usually used to protect life or property.
Lindane and chlordane were once used to protect wooden buildings from termites.
Typhus, trench fever, and bubonic plague are some of the diseases that body lice transmit.
During World War II, X bond is divided between Russia and the United States.
Zero is added to the bond dipole moment vectors.
The larger halogens have longer bonds but have weaker electronegativities.
The bond angles and other factors that vary with a specific molecule are what make it difficult to predict the dipole moments.
The table lists the measured dipole moments of the methanes.
There are four symmetrically oriented polar bonds of the carbon tetrahalides.
Predict which compound has the higher dipole moment and explain your reasoning.
The boiling points of alkyl halides are influenced by two types of intermolecular forces.
The strongest attraction in alkyl halides is the London force.
Higher boiling points are caused by larger London attractions.
The boiling points are affected by the X bond.
Molecules with higher weights have higher boiling points because they are slower moving and have more surface area.
The surface areas of the alkyl halides are different from the surface areas of the halogens.
We can figure out the relative surface areas of halogen atoms by looking at their van der Waals radii.
Butyl fluoride is 33 degrees centigrade.
The influence of chlorine's larger surface area is shown by butyl chloride.
The heavier halogens have larger surface areas.
The boiling points of the ethyl halides increase in order.
As a result of their smaller surface areas, compounds with branched, more spherical shapes have lower boiling points.
The boiling point of butyl bromide is 73 degrees.
This effect is similar to what we saw with alkanes.
Predict which compound has the higher boiling point for each pair of compounds.
If your prediction was correct, you need to explain why the compound has a higher boiling point.
The densities of alkyls halides are listed in Table 6-2.
Their densities are similar to their boiling points.
Alkyl fluorides and alkyl chlorides are less dense than water.
Alkyl chlorides with two or more chlorine atoms are denser than water.
Most alkyl halides exploit the chemistry of functional groups.
We review free-radical halogenation and summarize other, more useful, alkyl halides.
Subsequent chapters discuss the othereses.
Although we discussed its mechanism at length in Section 4-3, free-radical halogenation is not an effective method for the synthesis of alkyl halides.
There are different kinds of hydrogen atoms that can be separated.
Multiple substitutions can be given by more than one halogen atom.
A messy mixture of products can be caused by the chlorination of propane.
In industry, free-radical halogenation can be useful because the reagents are cheap, the mixture of products can be separated, and each of the individual products is sold separately.
A good yield of one product is required in a laboratory.
In the laboratory, free-radical halogenation is rarely used.
The following examples show the types of compounds that can be used in a laboratory.
All the hydrogen atoms in cyclohexane are the same, and free-radical chlorination gives a usable yield.
The formation of dichlorides and trichlorides can be done, but only with a small amount of chlorine and an excess of cyclohexane.
Free-radical bromination gives good yields of products with one type of hydrogen atom that is more reactive than the others.
A tertiary hydrogen atom is preferentially given a tertiary free radical by isobutane.
We don't use free-radical halogenation in the laboratory because it tends to be plagued by products.
In most cases, free-radical bromination of alkenes can be done in a highlyselective manner.
The charge or radical can be delocalized by resonance with the double bond.
A resonance-stabilized primary allylic radical can be formed with less energy than a typical secondary radical.
The most stable radical is the only one that can be formed by bromination.
The allylic radical is the most stable of the radicals that can be formed.
Consider the free-radical bromination of cyclohexene.
Under the right conditions, free-radical bromination of cyclohexene can give a good yield of 3-cyclohexene, where bromine has substituted for an allylic hydrogen on the carbon atom next to the double bond.
The mechanism is similar to others.
A bromine radical gives a resonance-stabilized allylic radical.
A bromine radical regenerated by this radical continues the chain reaction.
The general mechanism for allylic bromination shows that either end of the radical can give products.
One of the products has the bromine atom in the same position as the hydrogen atom.
The carbon atom that bears the radical in the second resonance form of the allylic radical results in the other product.
A large concentration of bromine is not good for allylic bromination because it can add to the double bond.
There is no need for another bromine because most samples contain traces of br2 to start the reaction.
Chapter 15 contains more detail on Allylic and benzylic halogenations.
The two products arise as a result of the resonance-stabilized intermediate.
A summary of the most important methods of making alkyl halides.
Many of them are more useful than free-radical halogenation.
The methods are not discussed until later in the text.
You can use this summary for reference throughout the course if they are listed here.
Many other functional groups are easily converted to alkyl halides.
An alkene can be given if X is lost from the alkyl halide.
In the elimination, the reagent B:- reacts as a base, abstracting a protons from the alkyl halide.
Depending on the alkyl halide and the reaction conditions, most nucleophiles can engage in either substitution or elimination.
substitution and elimination reactions compete with each other.
alkyl halides are our first examples of substitution and eliminations in Chapter 7.
Eliminating and substituting other types of compounds are encountered in later chapters.
The leaving group and the nucleophile are identified.
There are eliminations in Chapter 7.
The leaving halide ion is called X.
The reaction of iodomethane with hydroxide ion is an example.
Methanol is the product.
The carbon atom of iodomethane has a bond to a negative iodine atom.
The carbon atom has a partial positive charge when the electron density is drawn away from it.
The partial positive charge attracts the negative charge.
The back side of the carbon atom is attacked by Hydroxide ion, donating a pair of electrons to form a new bond.
Curved arrows show the movement of electron pairs from the electron-rich nucleophile to the electron-poor carbon atom.
As the carbon-oxygen bond begins to form, the carbon-iodine bond must break because carbon can only accommodate eight electrons.
Iodide ion leaves with a pair of electrons that once bond it to the carbon atom.
The one-step mechanism is supported by information.
We can change the concentrations of the reactants and observe the effects on the reaction rate.
The reaction is first in each of the reactants and second overall.
The rate equation is consistent with a mechanism that requires a collision between a molecule and an ion.
Both species are present in the transition state, and the collision frequencies are proportional to concentrations.
Bimolecular reactions have rate equations that are second order.
The bond to the leaving group is partially broken as a transition state is unstable and partially formed.
A transition state is not a molecule that can be isolated and is only an instant.
There is only one length of time shown in the diagram.
The transition state is only one energy maximum.
The leaving group is coordinated by the negative charge leaving.
The transition state involves a five-coordinate carbon atom with two partial bonds.
The Key Mechanism shows a reaction.
A transition state is created when a bond to the nucleophile is forming at the same time as the bond to the leaving group is breaking.
The reaction takes place in a single step.
The leaving group was forced to leave by a strong nucleophile.
The order of reactivity is CH3X.
The reaction of 1-bromobutane with sodium methoxide gives 1-methoxybutane.
1-methoxybutane can be formed at a rate of 0.05 mol>L per second under certain conditions.
Consider the reaction of 1-bromobutane with ammonia.
Draw the reactants and transition state.
The initial product is the salt of an amine, which is deprotonated by the excess ammo nia to give the amine.
A different combination of an alkoxide and an alkyl bromide is used to make 1-methoxybutane.
The SN2 mechanism has many useful reactions.
The alcohol comes from the reaction of an alkyl halide with a hydroxide ion.
A wide variety of functional groups can be converted by other nucleophiles.
The table summarizes some of the types of compounds that can be formed.
The syn thesizing of alkyl iodides and fluorides is more difficult to make than alkyl chlorides and bromides.
Iodide is a good nucleophilic and many alkyl chlorides give alkyl iodides.
Alkyl fluorides are difficult to synthesis directly, and they are often made by treating alkyl chlorides or bromides with a crown ether, which enhances the normally weak nucleophilic nature of the fluoride salt.
The factors that affect the rates and products of organic reactions will be studied using the SN2 reaction as an example.
The type of solvent used, as well as the nucleophile and the alkyl halide, are important.
The first thing we do is consider what makes a good nucleophile.
A "stronger" nucleophile is an ion or molecule that reacts faster in the SN2 reac tion than a "weaker" nucleophile under the same conditions.
A strong nucleophile is more effective than a weak one at attacking the carbon atom.
Methanol and methoxide ion have very similar pairs of nonbonding electrons, but methoxide ion reacts with more than one million times faster than methanol.
A species with a negative charge is a stronger nucleophile than a neutral one.
Nonbonding electrons are readily available for bonding.
The negative charge is shared by the oxygen of methoxide ion and the halide leaving group.
The transition state has a partial negative charge on the halide but a partial positive charge on the methanol oxygen atom.
It is possible to say that a base is always a stronger nucleophile than its conjugate acid.