Organic Chemistry Midterm Study

Chapters 1, 3, 4, 9

Ionic bond

EN difference greater than 2.0

Polar covalent bond

EN difference between 0.5-2.0

Nonpolar covalent bond

EN difference between 0-0.5

Formal charge

= how many valence does it like - how much is it using

Linear

SP, 180, 2 domains

Trigonal planar

SP2, 120, 3 domains

Tetrahedral

SP3 109.5, 4 domains

CH4

methane

C2H6

ethane

C3H8

propane

C4H10

butane

C5H12

pentane

C6H14

hexane

C7H16

heptane

C8H18

octane

C9H20

nonane

C10H22

decane

Alkane equation

C_nH_2n+2, representing saturated hydrocarbons

Cyclo (pentane, hexane, propane, butane)

Closed ring structures

No angle strain

5-6 membered rings

Angle strain

3-4 membered rings

What is unique about naming cyclic structures

start with alphabetical, then move to closest substituent

n-butyl

alphabetize by b

iso-butyl

(alphabetize this by first letter)

sec-butyl

alphabetize by b

tert-butyl

alphabetize by b

Isomer

Same formula, different compound

Constitutional isomer

Same formula, different compound due to order of atom connection

Compounds with ONE possible combo

methane, ethane, propane

Compounds with TWO possible combos

C4H10 (butane, methylpropane)

Compounds with THREE possible combos

C5H12 (pentane; 2-methylbutane; 2,2-dimethylpropane)

Compounds with FIVE possible combos

C6H14 (hexane; 3-methylpentane; 2,2-dimethylbutane; 2,3-dimethylbutane; 3,3-dimethylpentane)

Compounds with NINE possible combos

C10H22 (heptane; 2-methylhexane; 3-methylhexane; 2,2-dimethypentane; 2,3-dimethylpentane; 3,3-dimethylpentane; 3-ethylpentane; 2,2,3-trimethylbutane)

What are the two newman projection types

staggered and eclipsed

Which newman projection SPECIFIC type is the most stable

Staggered in anti (180 degree separation) (bonds are on opposite sides/spread max spread out)

Which newman projection type is the least stable

Eclipsed (bonds overlap and are closest to each other)

What kind of newman projection is being shown?

Gauge (60 degree separation)

What are two newman projections called that are identical in degree of separation?

degenerate

What is steric strain

Repulsion between electron clouds of close, unbonded atoms

What is the high point called, what is it associated with

energy maxima, eclipsed (unstable)

what is the low point called

energy minima, staggered (stable)

What is this?

Newman projection

What is this?

Chair conformation

Axial orientation

Straight up or down

Equatorial orientation

Leaning out and away

What is important about the boat conformer

The boat conformation is a less stable form of cyclohexane with two hydrogens eclipsing each other, leading to greater steric strain compared to chair conformations

Why is a major chair more stable than a minor chair

The steric strain is less with opposite sides not feeling presence, while same side feels greater steric repulsion due to eclipsing interactions

What are diaxial interactions

Diaxial interactions are steric interactions that occur between axial substituents on a cyclohexane ring, leading to increased strain and instability

What is a cis chair

A configuration of cyclohexane where substituents on adjacent carbon atoms are on the same side of the ring. This arrangement can lead to increased steric strain compared to its counter part (trans)

What is a trans chair

A configuration of cyclohexane where substituents on adjacent carbon atoms are on opposite sides of the ring. This arrangement minimizes steric strain compared to its counterpart (cis).

What is a stereoisomer and what does it include

A stereoisomer is a molecule with the same molecular formula, but differs in the three-dimensional orientation of its atoms. It includes cis/trans isomers and asymmetric centers (enantiomer + diatereomer)

What is an enantiomer

A type of stereoisomer that is a non-superimposable mirror image of another molecule, often involving asymmetric carbon atoms.

What is a cis-trans steroisomer

isomers that have groups that differ in position around a double bond or ring

What is a asymmetric center stereoisomer what types are there

• Asymmetric center stereoisomers contain one or more chiral centers, leading to distinct configurations

• enantiomers and diastereomers.

What is a diasteromer

isomers that are not mirror images of each other and may have multiple chiral centers

Example of cis-trans

cis 1-3 (both on hatch/solid wedge), trans 1-3 (one on hatch other on solid wedge)

What is chirality

property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of one or more chiral centers

What are characteristics of a chiral compound

nonsuperomposable (stackable on its mirror image), bonded to 4 different groups, optically inactive

What are characteristics of an achiral compound

Superimposable on its mirror image, may be identical, internal plane of symmetry

Characteristics of enantiomers

non-superimposable mirror images of each other, have same physical properties, differ in rotation of light and in living systems

What is this

Perspective drawing

How to name enantiomers

• Rank molecules based on mass

• Orient lowest priority (4) in the back (dashed wedge)

• Orient highest priority (1) in the front (hatch wedge)

• Draw a circle following 1 —> 2 etc.

• IMPORTANT NOTE: If you switch H to hatch, you made the enantiomer (original should be opposite, R becomes S vise versus)

What does it mean for a compound to be optically active?

The compound can rotate plane-polarized light due to the presence of chiral centers

What is the relation of achiral compounds and polarized light?

• do not rotate plane-polarized light

• optically inactive

Name this substituent

Methyl

Name this substituent

Ethyl

Name this substituent

Propyl

Name this substituent

Isopropyl

What is the relation of chiral compounds and polarized light?

• can rotate polarized light in a specific direction, either to the left (levorotatory) or to the right (dextrorotatory)

What is the difference btween “R” “S” and “l” “d”

first can be examined, second must be experimentally determined

What is observed rotation

the angle at which a chiral compound rotates plane-polarized light

What is specific rotation

standardized measure of a chiral compound's ability to rotate polarized light, expressed in degrees per g/mL in a 1.0 dm long @ specific T and wavelength

Relation os optical activity and “R” “S” enantiomers

rotate light in equal, opposite directions

What is a 50:50 mixture of R and S

racemic mixture (±)

What about racemic mixtures is important

they have 0 degree optical rotation

What do the yellow arrows represent

pairs of diastereomers

What is a meso compound?

• A compound that has multiple stereocenters

• achiral due to an internal plane of symmetry

What are the two qualifications of a meso compound

• must have 2+ chiral centers (C atoms bonded to 4 diff. molecules)

• Have same four attatchments to each chiral centerand an internal plane of symmetry.

What is a nucleophilic substitution reaction

A chemical reaction where a nucleophile replaces a leaving group in a molecule, resulting in the formation of a new product

What is an alkyl halide

• A hydrocarbon backbone w/ halogens

• different chemical and physical properties than normal hydrocarbons

What is bond polarity?

Bond polarity refers to the distribution of electrical charge over the atoms involved in a bond, resulting from differences in electronegativity

Why do alkyl halides have different properties and what effects are seen

bond polarity, physical effects, chemical effects

What physical effects are there in alkyl halides

• molecules with polar bonds stick together (higher bp)

• higher solubility in water (polar in polar)

What chemical effects are there in alkyl halides

• +/- interaction can be overcome (atom breaking off)

• polarity (often) increases chemical reactivity

Alkyl halides are _____

Polar

What is a substrate

the main organic molecule experimented on

SN2 reactions are ___ ____

one step

how a reaction occurs =

mechanism

each step requires __________ ______ where uphill is bond ______ and downhill is bond ______ and is ____  in energy than the beginning

activation energy, formation, breaking, lower 

SN2 reactantion

nucleophile + substrate → product + leaving group

SN2 rates are represented by what equation

rate = k[OH-][CH3Br]

What is present at the Transition State

nucleophile and substrate

What kind of reaction is a SN2

Bimolecular (2 molecules are involved in the Ts of the RDS)

What is the slowest step called

rate-determining step (RDS)

Kinetics and SN2 reactions

• concentrating chemicals in the RDS will speed up the reaction

• Adding chemicals not involved in RDS will not speed up the reaction

What is a backside attack

A mechanism in SN2 reactions where the nucleophile approaches the electrophile from the opposite side of the leaving group, leading to inversion of stereochemistry (opposite configuration)

What are steric effects of SN2

the size and spatial arrangement of substituents around the electrophile can facilitate nucleophilic attack, influencing reaction rates and outcomes

Order of most reactive to least/too unreactive (order of increasing steric hinderince)

methyl > primary > secondary > tertiary

Relative basicities of halide ions (most to least stable)

I- > Br- > Cl- > F-

Relative basicities of halide (most to least stable)

RI > RBr > RCl > RF