Orgo Lecture 1

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alkane

carbon-carbon single bond or methane

alkene

carbon-carbon double bond

alkyne

carbon-carbon triple bond

alcohol

R-OH

ether

R-O-R

carboxylic acid

amide

the R" and R' can be H

alkyl

an alkyl group is an alkane missing one hydrogen

gem-dihalide

vic-dihalide

hydroxyl

-OH

alkoxy

-OR

hemiacetal

mesyl group

Ms--

tosyl group

Ts--

acetyl

contains a methyl group single-bonded to a carbonyl

aryl

-Ar, -C6H5

meth

1

prop

3

pent

5

hept

7

dec

10

IUPAC rules for nomenclature

* the longest carbon chain with the most substituents determines the base name
* the end carbon closet to a carbon with a substituent is always the first carbon. in the case of a tie, look to the next substituent
* any substituent is given the same number as its carbon
* if the same substituent is used more than once, use the prefixes di-, tri-, tetra, and so on
* order the substituents alphabetically (ignore prefix)

electrostatic force

force between the electrons and the nuclei that creates all molecular bonds.

coordinate covalent bond

one nucleus can donate both electrons

sigma-bond

when the bonding pair of electrons are localized directly between the two bonding atoms.

pi-bond

additional bonds between two sigma bonded atoms. more reactive. prevent rotation.

sp3 bond angles

109.5 degrees

dsp3

90 degrees, 120 degrees

d2sp3

90

four rules for resonance

1) atoms must not be moved. move electrons
2) number of unpaired electrons must remain constant
3) resonance atoms must lie in the same plane
4) only proper Lewis structures allowed

two conditions must exist for resonance to occur

1) a species must contain an atom either with a p orbital or an unshared pair of electrons
2) that atom must be single bonded to an atom that posses a double or triple bond.

Huckel's rule

planar monocylic rings with 4n+2 pi-electrons) should be aromatic (display resonance)

dipole moment

occurs when the center of positive charge on a molecule does not coincide with the center of negative charge.
μ=qd

induced dipoles

can be induced in an otherwise nonpolar molecule by a polar molecule, ion, or electric field.

instantaneous dipole moment

can exist in an otherwise nonpolar molecule. arise because the electrons in a bond move about the orbital, and at any given moment may not be distributed exactly between the two bonding atoms even when the atoms are identical.

intermolecular attractions

occur solely due to dipole moments. generally about 1% as strong as covalent bonds.

London Dispersion Forces

the weakest dipole-dipole force is between two instantaneous dipoles. weak, but responsible for phase changes

isomers

unique molecules with the same molecular formula

conformational isomers

not true isomers. different spatial orientations of the same molecule

structural isomer

have the same molecular formula, but different bond-to-bond connectivity

chirality

handedness

chiral molecules

molecules that have 'handedness'. differ from reflection.

achiral molecules

exactly the same as their reflections

chiral carbon

when attached to four different substituents

absolute configuration

the only way to physically describe the orientation of atoms around a chiral center.
1) number atoms attached to the chiral center from highest to lowest priority. largest atomic weights are given the highest priority
2) if two atoms have the same element, then their substituents are sequentially compared in order of decreasing priority until one of the substituents is found to have a greater priority than the corresponding substituent on the other carbon.
3) substituents on double and triple bonds are counted two and three times respectively
4) make lowest priority group face away, and see which direction highest to lowest

absolute configuration of R

indicated by a clockwise circle.

absolute configuration of S

indicated by a counterclockwise circle.

relative configuration

not related to absolute configuration. molecules have the same _____ _____ about a carbon if they differ by only one substituent and the other substituents are oriented identically about the carbon. this orientation is inverted in an Sn2 reaction.

observed rotation

the direction and degree to which a compound rotates plane polarized light.

polarimeter

screens out photons with all but one orientation of electric field.

plane-polarized light

the resulting light from a polarimeter consists of photons with their electric fields oriented in the same direction.

optically inactive

no rotation of the plane or electric field by a typical compound. may be compounds with no chiral center

racemic mixture

chiral compounds containing equal amounts of both stereoisomers

optically active compound

rotates plane-polarized light.

rotates light clockwise

designated '+' or 'd'

rotates light counterclockwise

designated '-' or 'l'

observed rotation

the direction and number of degrees that the electric field in plane-polarized light rotates when it passes through a compound is called that compounds ____ ____.

specific rotation

simply a standardized form of observed rotation that is arrived at through calculations using observed rotation and experimental parameters.

enantiomers

have the same molecular formula, have the same bond-to-bond connectivity, are mirror images of each other, but are not the same molecule. must have opposite absolute configurations at each chiral carbon.

rotate plane polarized light in opposite directions

aside from reactions with plane-polarized light and with other chiral compounds, have the same physical and chemical properties.

optical purity

refers to the ratio of actual rotation to the rotation of a pure sample.

enantiomeric purity

the ratio of pure enantiomer to racemic mixture. optical purity equals ___ ____ for any mixture of enantiomers

resolution

the separation of enantiomers

diastereomers

have the same molecular formula, have the same bond-to-bond connectivity, are NOT mirror images to each other, and are not the same compounds.

geometric isomer

exist due to hindered rotation about a bond. rotation may be hindered due to ring structure, double or triple bond. have different physical properties.

cis-isomers

molecules with same side substituents. have dipole moment. stronger intermolecular forces leading to higher boiling points. less symmetry so fewer crystals, thus lower melting points.

trans-isomers

molecules with opposite-side substituents. do not have dipole moment.

steric hindrance

substituent groups in the cis position may crowd each other. produces higher energy levels resulting in higher heats of combustion.

system to describe geometric isomers unambiguously

two substituents on each carbon are prioritized by atomic weight. labeled E or Z.

E (entegen)

higher priority substituents exist on opposite sides

Z (zusammen)

higher priority substituents exist on the same side.

maximum number of optically active isomers in a single compound.

2ⁿ, where n is the number of chiral centers.

meso compounds

two chiral centers in a single molecule may offset each other. have a plane of symmetry through their center which divides them into two halves that are mirror images of each other. achiral and optically inactive.

epimers

diastereomers that differ at only one chiral carbon.

anomers

if a ring closure occurs at the epimeric carbon, two possible diastereomers called ______. distinguished by the orientation of their substituents. α and β.

anomeric carbon

the chiral carbon of an anomer.

Fisher Projections

vertical lines are assumed to be oriented into the page. horizontal lines are assumed to be oriented out of the page.

Newman projection

a view straight down the axis of one of the σ-bond. both the intersecting lines and the large circle are assumed to be carbon atoms.

index of hydrogen deficiency

indicates the number of pairs of hydrogens a compound is required in order to become a saturated alkane.

tert-butyl

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