Orgo review

Question 1

Explain the difference between sigma and pi bonds

Answer 1

Sigma bonds are the result of end-to-end overlap of orbitals and make single bonds.

Pi bonds are the result of side-to-side overlap of overbitals and result in double or triple bonds.

Question 2

Explain the difference between sp, sp² and sp³-hybridized carbon atoms.

Answer 2

sp carbons have two groups bonded to them and have a 180 degree bond angle between those groups

sp² carbon atoms have three groups bonded 120 degrees apart

sp³ carbons have four groups bonded and are 109.5 degrees apart

Question 3

Define unsaturated

Answer 3

An unsaturated molecule contains one or more pi bonds, such that it does not contain the maximum amount of hydrogen

Question 4

Rank the four types of carbocations from least to most stable

Answer 4

Methyl, primary, secondaey, tertiary

Question 5

Explain the difference between structural isomers, conformational isomers, and stereoisomers

Answer 5

Structural isomers are two molecules that have the same molecular formula, but different connectivity

Conformational isomers have the same molecular formula, but differ in their rotations about single bonds.

Stereoisomers have the same molecular formula and connectivity of atoms, but the groups differ in spatial arrangements in the molecule.

Question 6

What is another name for geometric isomers?

Answer 6

Geometric isomers are a type of diastereomer. They can also be referred to as cis/trans isomers about a double bond or ring.

Question 7

What are two types of stereoisomers

Answer 7

Geometric isomers and optical isomers are stereoisomers

Question 8

What is the most stable conformation of methylcyclohexane?

Answer 8

The chair form with an equatorial position (Pointing to the side)

Question 9

What is a racemic mixture?

Answer 9

A 50/50 mixture of two enantiomers

Question 10

What is a nucleophile?

What is an electrophile?

Answer 10

A nucleophile is a species that is electron rich and is attracted to something that is electron deficient to donate a pair of electrons. It usually has a full or partial negative charge and/or a lone pair of electrons

An electrophile is a species that is electron deficient, so it is attracked to electron rich species. It usually has a faull or partial positive charge associated with it.

Question 11

Define Lewis acid and Lewis Base

Answer 11

A Lewis acid is an electron pair acceptor, or an electrophile.

A lewis base is an electron pair donor, or nucleophile.

Question 12

Is inversion of configuration seen in an S_n1 or S_n2 reaction?

Which yields a racemic mixture

Answer 12

Sn2 reaction results in inversion of configuration

Sn1 results in a racemic mixture

Question 13

Which will a more substituted substrate favor, Sn1 or SN2?

Answer 13

Sn1 is favored, because the first step is the formation of a carbocation, and more substituted carbocations are more stable.

Question 14

Which reaction mechanism (Sn1/Sn2) is dependent on nucleophile concentration?

Answer 14

Sn2 is dependent on nucleophile concentration

Question 15

What type of isomers are tautomers?

Answer 15

Structural isomers

Question 16

What is the difference between a hydride, a proton, and a hydrogen?

Answer 16

A hydride is H^-, a proton is H⁺ and a hydrogen is H* (radical)

Question 17

What is an imine?

Answer 17

The nitrogen equivalent to a ketone or aldehyde

Question 18

What type of mechanism is the saponification of a triglyceride?

Answer 18

Saponification is an addition-elimination reaction

Question 19

Name the carboxylic acid derivatives from least to most reactive

Answer 19

Amide, ester, acid anhydride, acid halide

Question 20

Give the approximate infrared stretching frequencies for the following functional groups:

O-H C=O C=C

Answer 20

O-H 3,200-3600 cm^-1

C=O 1,700 cm^-1

C=C 1,650 cm^-1

Question 21

What does the splitting in a ¹H NMR spectrum indicate?

What does the number of signals in the spectrum show?

Answer 21

The number of nonequivalent hydrogens on the adjacent carbon atoms

The number of nonequivalent hydrogens in the molecule

Question 22

Are molecules with five or fewer carbons that also bear a functional group more soluble in the aqueous or organic layer in an extraction?

Answer 22

Molecules with <5 carbonds are more soluble in the aqueous layer

Question 23

What functional groups can be manipulated in an extraction to alter the solubility of a molecule?

Answer 23

Carboxylic acids, phenols, and amines

Question 24

Do polar or nonpolar molecules have lower R_f values?

Answer 24

Polar molecules have lower R_f values

Question 25

For each chromatographic technique, name the property that is key to their function

TLC, GC, SEC, affinity chromatography, and ion exchange

Answer 25

TLC - polarity

GC - polarity and boiling point

SEC - size

Affinity - IMF

Ion exchange - charge and size

Question 26

Are animal amino acids in the D or L configuration?

Answer 26

L

Question 27

What are two common techniques to synthesize amino acids?

Answer 27

Strecker and Gabriel-malonic ester syntheses