Chapter 4 Orgo

Select the correct order of priority for the groups bonded to the stereogenic center in the molecule shown, from the highest priority (1) to the lowest priority (4). Place the group with the highest priority first. http://i64.tinypic.com/k2k7xk.png H CH=CH2 OH CH3

(1) OH (bc it has the highest atomic number) (2) CH=CH2 (3) CH3 (bc it has a higher atomic number than H) (4) H (lowest atomic number)

How many steroisomers exist for the compound shown http://i64.tinypic.com/r6y6g6.png 0 3 2 4

3

A mixture contains 65% of a compound and 35% of its enantiomer. The % e.e of the mixture is equal to ......

30%

How many stereoisomers are possible for the compound shown with a fixed geometric arrangement at the double bond. http://i68.tinypic.com/fmkqy0.png

4 (There are two chirality centers and the double bond corresponds to a specific geometric isomer in the structure shown. Hence, there are 2^2 = stereoisomers.

Select the correct Fischer projection for the molecule shown. http://i64.tinypic.com/o7sykj.png

A

Which of the following cannot be stereogenic centers in any molecule? Select all that apply. A carbonyl C atom Any quaternary C atom A C atom of a C=C double bond CH3 groups A ring C atom

A carbonyl C atom A C atom of a C=C double bond CH3 groups

Which of the following statements correctly describe a meso compound? Select all that apply. A meso compound is not superimposable upon its mirror image A meso compound contains a plane of symmetry A meso compound contains no chirality centers A meso compound is optically inactive A meso compound is achiral.

A meso compound contains a plane of symmetry A meso compound is optically inactive A meso compound is achiral.

The term absolute configuration refers to ______. A particular spatial arrangement of reacting species A particular 3D spatial arrangement of groups at a chirality center A particular 3D grouping of molecules A particular 2D arrangement of atoms in a molecule

A particular 3D spatial arrangement of groups at a chirality center

Which of the following features MUST be present for a compound to have a meso form? Select all that apply. No chirality centers A chirality axis A plane of symmetry A circle of symmetry Two or more chirality centers

A plane of symmetry Two or more chirality centers

Select all the Fischer projections that represent meso compounds. http://i63.tinypic.com/2uh496w.png

A, D (exchange the 3 groups on the upper chirality center to see the plane of symmetry)

Select the Fischer projection that correctly represents the wedge-dash structure shown. http://i65.tinypic.com/2uygklf.png A B C

B

Which of the Fischer projections shown depict chiral compounds? http://i68.tinypic.com/2qarbza.png A B C D

B, D

Which wedge-dash structure corresponds to the Fischer projection shown? http://i64.tinypic.com/142spch.png A B C

C

In order for a sample to be optically active it must contain at least one _____ substance and one _______ must be present in excess of the other.

Chiral, enantiomer

Which of the following best defines diastereomers? Diastereoemers are stereomers that are not mirror images of each other. Diastereomers are stereomers that are mirror images of each other. Diastereomers are constitutional isomers that are mirror images of each other. Diastereomers are constitutional isomers that are not mirror images of each other.

Diastereoemers are stereomers that are not mirror images of each other.

A Fischer projection can be manipulated in various ways what relationship will the resulting structure have to the original for each of the following manipulations. (an example of a Fischer projection is shown) http://i67.tinypic.com/2wbrjiw.png Two categories: Enantiomer or identical switching any two groups switching any three groups rotating the entire structure by 180 degrees

Enantiomer: switching any two groups Identical: Switching any three groups Rotating the entire structure by 180 degrees

Select all the statements that correctly describe the optical activity of two enantiomers. Enantiomers are optically inactive. Enantiomers will rotate plane-polarized light by the same amount. Enantiomers will have identical optical activity. Enantiomers will rotate plane-polarized light in opposite directions.

Enantiomers will rotate plane-polarized light by the same amount. Enantiomers will rotate plane-polarized light in opposite directions.

True or false: A chiral molecule and a chirality center are one and the same.

False (a chiral molecule is one that cannot be superimposed on its mirror image, whereas a chirality center is a single tetrahedral C atom that is bonded to four different groups. Generally, a molecule must contain at least one chirality center to be chiral.)

Consider the general structure shown, which contains a C atom bonded to four different atoms or groups. If any of these two atoms or groups are exchanged, which of the following statements will be correct? http://i68.tinypic.com/anoboy.png Check all that will apply I.) The resulting structure will not be superimposable upon the original II.) The resulting structure will be identical to the original III.) The structure is converted to its enantiomer IV.) The resulting structure is a constitutional isomer of the original

I.) The resulting structure will not be superimposable upon the original III.) The structure is converted to its enantiomer

Which of the marked atoms in the structure shown are chirality centers? Select all that apply. http://i68.tinypic.com/dy9guh.png I.) c II.) b III.) d IV.) a

I.) c II.) b

A stereogenic C atom is one that has four different groups attached to it. Which of the following are not stereogenic centers by this definitions? (select all that apply.) I.) sp3-hybridized C atoms II.) sp2-hybridized C atoms III.) CH groups IV.) CH2 groups V.) CH3 groups

II.) sp2-hybridized C atoms IV.) CH2 groups V.) CH3 groups

Which of the following are rules used to assign a priority to each group bonded to a stereogenic center? Select all that apply. If two isotopes are bonded to the stereogenic center, the isotope with the higher mass number has a higher priority. To assign a priority to an atom that is part of a multiple bond, give the highest priority to a triply bonded. If two isotopes are bonded to the stereogenic center, the isotope with the lower mass number has a higher priority. To assign a priority to an atom that is part of a multiple bond, treat the multiply bonded atom as an equivalent number of singly bonded atoms.

If two isotopes are bonded to the stereogenic center, the isotope with the higher mass number has a higher priority. To assign a priority to an atom that is part of a multiple bond, treat the multiply bonded atom as an equivalent number of singly bonded atoms.

Which of the following physical properties are identical for two enantiomers? Select all that apply. Interaction with plane-polarized light Melting point Solubility Boiling point

Melting point Solubility Boiling point

Select the correct order of priority for the groups bonded to the stereogenic center in the molecule shown, from the highest priority (1) to the lowest priority (4). Place the group with the highest priority first. CH2OH CH3 H NH2

NH2 CH2OH CH3 H

Designate the configuration of the stereogenic center in the structure shown as R or S. http://i64.tinypic.com/ra0pk7.png

R

The absolute configuration at the chirality center in the Fischer projection shown is _______. http://i65.tinypic.com/zxqg50.png

R

Select all the statements that correctly include the elements of the Cahn-Ingold-Prelog approach to absolute configurations. Rules were developed for ranking substituents at each carbon atom. Rules were developed for ranking substituents at the chirality center. A protocol was developed for viewing the spatial orientation at the chirality center.

Rules were developed for ranking substituents at the chirality center. A protocol was developed for viewing the spatial orientation at the chirality center.

Match each structure to the correct description. http://i66.tinypic.com/1z3wm1i.png Structure A ? Structure B ? meso compound chiral compound

Structure A : meso compound Structure B : chiral compound

Match each structure to the correct description of its relationship to the cycloalkane shown. http://i63.tinypic.com/2n6dfkp.png Structure X ? Structure Y ? Structure Z ? Diastereomer Identical compound Enantiomer

Structure X : enantiomer Structure Y : diastereomer Structure Z : identical compound

From the selections below, match the structure of each compound with the correct description of its stereochemical relationship to Structure A. http://i63.tinypic.com/2ntvf6.png Structure X ? Structure Y ? diastereomer enantiomer

Structure X enantiomer Structure Y diastereomer

Which of following conditions must be fulfilled for a ring carbon to be a chirality center? Select all that apply. The path traced around the ring from that carbon atom is one direction must be the same as the path traced in the other direction. The carbon atom must bear two different substituents, other than the ring C atoms. The path traced around the ring from that carbon atom in one direction must be different from the path traced in the other direction. The carbon atom cannot be bonded to any hydrogen atoms.

The carbon atom must bear two different substituents, other than the ring C atoms. The path traced around the ring from that carbon atom in one direction must be different from the path traced in the other direction.

The figure shown illustrates the general structure of a Fischer projection. Select all that correctly describe how to interpret this projection. http://i68.tinypic.com/2z4wumg.png Group a is always the lowest priority group The carbon of the chirality center lies at the center of the cross The bonds to groups a and d project away from the viewer The bonds to groups a and c project away from the viewer.

The carbon of the chirality center lies at the center of the cross The bonds to groups a and c project away from the viewer.

Which of the following conditions must be fulfilled for a sample to be optically active? Select all that apply. The sample cannot be a mixture of stereoisomers The sample must contain a chiral substance One enantiomer must be present in greater quantity than the other The sample cannot contain achiral substances

The sample must contain a chiral substance One enantiomer must be present in greater quantity than the other

Select all the statements that correctly describe how to draw a Fischer projection for a molecule with 2 chirality centers. The horizontal lines represent bonds pointing away from the viewer. The chirality centers are arranged horizontally next to each other. The vertical lines represent bonds pointing away from the viewer. The molecule is arranged in an eclipsed conformation for the projection

The vertical lines represent bonds pointing away from the viewer. The molecule is arranged in an eclipsed conformation for the projection

True or false: Absolute configuration cannot be determined from the optical rotation of a sample.

True

Which of the following features MUST be present for a compound to have meso form? A circle of symmetry Two or more chirality centers A chirality axis No chirality centers A plane of symmetry

Two or more chirality centers A plane of symmetry

What are enantiomers? a.) Enantiomers are mirror image molecules that are not superimposible b.) Enantiomers are mirror image molecules that are superimposable c.) Enantiomers are molecules that are not mirror images and are not superimposable d.) Enantiomers are molecules that are not mirror images but that are superimposable

a.) Enantiomers are mirror image molecules that are not superimposible

Which of the following statements correctly describes a racemic mixture? a.) The mixture is not optically active because the two enantiomers show equal but opposite rotations, which therefore cancel. b.) The mixture is not optically active because a mixture of two enantiomers is achiral. c.) The mixture is optically active because each enantiomer in the mixture is still optically active.

a.) The mixture is not optically active because the two enantiomers show equal but opposite rotations, which therefore cancel.

Which of the following best describes the relationship between the absolute configuration at a chirality center and the optical rotation of a compound? a.) There is no relationship between absolute configuration and optical rotation b.) The magnitude of the optical rotation indicates the absolute configuration c.) The sign of the optical rotation indicates the absolute configuration

a.) There is no relationship between absolute configuration and optical rotation

Define a chiral molecule a.) nonsuperimposable upon its mirror image b.) can be superimposed upon its mirror image

a.) nonsuperimposable upon its mirror image

Define an achiral molecule a.) nonsuperimposable upon its mirror image b.) can be superimposed upon its mirror image

b.) can be superimposed upon its mirror image

Is the structure shown chiral or achiral? http://i64.tinypic.com/29bc4ye.png a.) chiral, because it can be superimposed upon its mirror image b.) chiral, because it cannot be superimposed upon its mirror image c.) achiral, because it cannot be superimposed upon its mirror image d.) achiral, because it can be superimposed upon its mirror image

b.) chiral, because it cannot be superimposed upon its mirror image

The presence of a plane of center of symmetry will cause a molecule to be ______ upon its mirror image and it will therefore be _______. a.) nonsuperimposable, chiral b.) superimposed, achiral c.) nonsuperimposable, achiral d.) superimposable, chiral

b.) superimposed, achiral

Which of the following descriptions is correct for a molecule that contains a plane of symmetry? a.) The molecule has at least one C atom with two identical group attached to it. b.) The molecule as more than one functional group of the same type c.) One half of the molecule is a mirror image of the other half.

c.) One half of the molecule is a mirror image of the other half.

The molecule shown is _______ because it _______ be superimposed upon its mirror image. a.) chiral, cannot b.) achiral, cannot c.) achiral, can d.) chiral, can

c.) achiral, can

It is generally true that for a simple molecule such as the one shown, exchange of any of the two substituents will convert the structure to the ______, whereas an exchange of three of the substituents will convert the structure to the _____. http://i66.tinypic.com/2s0gv1g.png a.) enantiomer, constitutional isomeer b.) original molecule, enantiomer c.) enantiomer, original molecule d.) constitutional isomer, original molecule

c.) enantiomer, original molecule

Are chiral and achiral views optically active or inactive?

chiral : optically active achiral : optically inactive

A molecule that cannot be superimposed upon its mirror image is described as _______ whereas a tetrahedral carbon atom bonded to 4 different substituents is described as a(n) ______ center.

chiral, chirality

A Fischer projection represents a tetrahedral center using two crossed lines. The center of the cross represents the _______ center although this carbon is not explicitly shown. The ________ bonds of the projection are directed toward the viewer and the ______ bonds are directed away from the viewer.

chirality, horizontal, vertical

Optically active compounds rotate plane-polarized light. Match the direction of rotation with the correct term. clockwise ? counterclockwise ? levorotatory dextrorotatory

clockwise : dextrorotatory counterclockwise : levorotatory

If a compound rotates plane-polarized light in a ______ direction, the compound is called dextrorotatory. The rotation is labeled d or _________. Rotation for a levorotatory compound is labeled I or _______.

clockwise, (+), -

Which of the following statements correctly describes a racemic mixture? a.) A mixture of two enantiomers that is still optically active b.) A mixture containing equal amounts of two diastereomers c.) A mixture containing equal amounts of two meso compounds d.) A mixture containing equal amounts of two enantiomers

d.) A mixture containing equal amounts of two enantiomers

Which of the following correctly describes a chirality center? a.) A carbon atom that is not bonded to any H atoms b.) A carbon atom that is identical to its mirror image c.) A carbon atom that has a mirror image d.) A tetrahedral carbon atom bonded to four different atoms or groups

d.) A tetrahedral carbon atom bonded to four different atoms or groups

Which of the following best explains what the enantiomeric excess of a mixture is? a.) The enantiomeric excess indicates how much more soluble one enantiomer is than the other. b.) The enantiomeric excess indicates how much more reactive one enantiomer is than the other. c.) The enantiomeric excess tells how much more of one enantiomer must be added to achieve a racemic mixture. d.) The enantiomeric excess indicates how much more of one enantiomer there is in a mixture.

d.) The enantiomeric excess indicates how much more of one enantiomer there is in a mixture.

What is the observed rotation of a sample? a.) The observed rotation is the angle symbol by which an achiral compound rotates the plane of polarized light in a polarimeter b.) The observed rotation is the angle symbol by which a chiral compound rotates the plane of ordinary light in a polarimeter c.) The observed rotation is the angle symbol by which an achiral compound rotate the plane of ordinary light in a polarimeter. d.) The observed rotation is the angle symbol by which an chiral compound rotates the plane of polarized light in a polarimeter

d.) The observed rotation is the angle symbol by which an chiral compound rotates the plane of polarized light in a polarimeter

A meso compound is a(n) ______ compound that has _____ chirality centers. a.) achiral, no b.) chiral, two or more c.) chiral, no d.) achiral, two or more

d.) achiral, two or more

When drawing the Fischer projection for a molecule with 2 chirality centers, the molecule is arranged in a(n) _________ conformation for projection onto the page. staggered gauche eclipsed

eclipsed

The _______ excess, also called the optical ______, tells how much more there is of one enantiomer than the other in the mixture.

enantiomeric, purity

Two enantiomers rotate plane-polarized light in exactly _______ amounts but in _____ directions.

equal, opposite

Match each structure with the correct description of its symmetry. http://i65.tinypic.com/1zqyi2v.png has a plane of symmetry has a center of symmetry has neither a plane nor a center of symmetry

has a plane of symmetry : C, D has a center of symmetry : A has neither a plane nor a center of symmetry : B

Enantiomers are compounds that are mirror images of each other, and their physical properties are therefore ______. Diastereomers are ______-isomers but they do not have mirror image relationship, and their physical properties are therefore ______, except when they interact with a chiral environment.

identical, stereo, different

Enantiomers are... nonsuperimosable mirror images or stereoisomers that are not mirror images

nonsuperimosable mirror images

A compound that rotates the plane of plane-polarized light is said to be _______ active.

optically

If the structure of a molecule is such that one half of the molecule is a mirror image of the other half, the molecule is said to have a _____ of ______.

plane of symmetry

If a molecule a(n) ______ or _____ of symmetry it will be superimposable upon its mirror image and it will therefore be _____

plane, center, achiral

The _____ rotation [symbol half infinity sign] is a physical constant that is calculated by measuring the _____ rotation of a sample in a tube with a defined length at a specific temperature, concentration, and wavelength. observed, specific specific, observed

specific, observed

Diastereomers are... nonsuperimosable mirror images or stereoisomers that are not mirror images

stereoisomers that are not mirror images

The terms erythro and threo are used to describe the relationship between the Fischer projections of two diastereomers. Match term with correct description. theo ? erythro ? like substituents on opposite sides of the projection like substituents on the same side of the projection

theo : like substituents on opposite sides of the projection erytheo : like substituents on the same side of the projection

A carbon atom in a ring can be a chirality center if it bears ________ different groups (other than the adjacent ring C atoms) and the path traced around the ring in one direction is _________ from that traced in the other.

two, different