chem 2510 midterm one

organic chemistry I - with Dr. Chang :)

organic chemistry

concerns compounds that contain carbon and hydrogen

heteroatoms

atoms that are not carbon and hydrogen, but can be present in organic compounds

valence electrons

only electrons in an atom that are used for bonding

s orbital

1 orbital - holds up to 2 electrons

p orbital

3 orbitals - holds up to 6 electrons

node

found in p orbital, site where there is no electron density

ionic

electrons are completely transferred

covalent bond

electrons are shared between two atoms

polar covalent bond

electrons are unequally shared

nonpolar covalent bonds

electrons are equally shared

lewis structure

tell us about the atom connectivity, but does not tell us anything about molecular geometry

octet rule

every atom in a compound must have 8 total valence electrons surrounding it

formal charge

valence electrons - (bonding e-/2) - (nonbonding e-)

carbocation

carbon with 3 bonds only; positive 1 formal charge

carboanion

carbon with 3 bonds and 1 lone pair; negative formal charge

nitrogen with FC +1

nitrogen with four bonds

nitrogen with FC -1

nitrogen with 2 bonds and 2 lone pairs

oxygen with FC +1

oxygen with 3 bonds and 1 lone pair

oxygen with FC -1

oxygen with one bond and 3 lone pairs

resonance structure

same atom position, different electron position

electron pushing arrow

show electron movement

LCD

lone pair next to cation

lone pair next to pi bond

cation next to pi bond

requirements to be the major resonance contributor

1. MUST FILL ALL ATOMS OCTET

2. negative charge on the most electronegative atom

3. formal charges as less as possible

thiol

R-S-H

thioether

R-S-R

1 degree amine

amine attached to one carbon

2 degree amine

amine attached to two carbons

3 degree amine

amine attached to 3 carbons

1 degree amide

amide attached to one carbon

2 degree amide

amide attached to two carbons

3 degree amide

amide attached to three carbons

lactone

cyclic ester

lactam

cyclic amide

alkane

single bonds between C only

haloalkane

C-X

alcohol

-OH

ether

R-O-R

alkene

double bond between carbon and carbon

alkyne

triple bond between carbon and carbon

aldehyde

R-CO-H

ketone

R-CO-R

carboxylic acid

-COOH

anhydride

R-(carbonyl)-O-(carbonyl)-R

ester

R-CO-O-R

amide

R-CO-N-2(R)

nitriles

C tripled bonded to N

2 isomers of butane

n-butane and iso-butane

3 isomers of pentane

n-pentane, iso-pentane, and neo-pentane

naming simple alkanes

1. find longest chain with most substituents

2. classify the groups on parent chain

3. label carbon from end that is closest to a group

4. alphabetical order

aromatic ring

3 double bonds incorporated in a 6 membered ring

alkyl group

alkane - 1 H

amine

3 Rs singly bonded to a N

primary carbon

carbon attached to one other carbon, has primary hydrogens

secondary carbon

carbon attached to two other carbon, has secondary hydrogens

tertiary carbon

carbon is attached to three other carbons, has tertiary hydrogens

quaternary carbon

carbon is attached to four other carbons

two conformations of ethane

1. staggered (stable)

2. eclipsed (unstable)

torsional strain

the change in energy from staggered conformation to eclipsed formation

torsional angle

degree of rotation, dihedral angle

staggered conformaton

torsional angle is 60 degrees; stable form

eclipsed form

torsional angle is 0 degrees; the components overlap each other

anti conformation

staggered form that has torsional angle of 180 degrees

gauche conformation

staggered form that has a torsional angle of 60 degrees

isobutyl group

3 carbon chain with one methyl group on carbon 2

sec-butyl

branched structure at the 1st carbon of the 3 carbon branched chain

tert-butyl

1,1-dimethylethyl

IUPAC name of sec-butyl

1-methylpropyl

IUPAC name of isobutyl

2-methylpropyl

IUPAC name of iso-propyl

1-methylethyl

BL acid

proton donor

BL base

proton acceptor

equlibrium direction in ABRxns

1. low stability to high stability

2. strong acid to weak acid

3. low pka to high pka

four factors that affect conjugate base stability

1. elemental affect

2. resonance

3. induction

4. hybridization

lewis acid

electron pair acceptor

lewis base

electron pair donor

electrophile

positive charge molecules that are attracted to electrons

nucleophile

negative charged molecules that want to get ride of electrons

chair conformation of cyclohexane

no eclipsing and bonding strain (bond angles are nearly tetrahedral), 4 carbons are on the same plane, while one carbon is above the plane and the other carbon is below the plane

boat form

carbon one and carbon four are off the plane in the same direction; creates transannular strain

transannular strain

strain resulting from the steric crowding of 2 groups across the ring

Twist boat

twist of one of the CC bonds, partial removal of the transannular strain - 2 forms possible

cyclohexane chair flip

1. chair

2. half-chair

3. twist

4. boat

5. twist

6. half-chair

7. flipped chair

axial

C-H bonds are nearly parallels to the principle molecular axis

equatorial

C-H bonds are nearly perpendicular to the axis

chair flip

leads to axial hydrogens becoming equatorial and the equatorial hydrogens to become axial

1,3-diaxial interaction

steric repulsion between substituent and hydrogens on carbon 1 and carbon 3/5

A-value

energy penalty for placing a group on axial position

molecular weight and A-value

increasing the molecular weight of the substituent increases the A-value

bold wedge

up

dashed wedge

down

cis

two bold wedges or two dashed wedges

trans

one bold wedge and one dashed wedge

half chair

one carbon is on a different plane, the most unstable conformer

after a chair flip:

1. up → up , down → down

2. axial → equatorial, equatorial → axial

change in G

products minus reactants (only takes axial sub. into account)

stability of chair conformation increases

if axial number of substituents decreases and equatorial number of substituents increases

disubstituted cyclohexane

stability increases if the bulkier substituent if on the equatorial position, while the smaller substituent is on the axial position

bicyclic name nomenclature

bicyclo[number of carbons on one side. number of carbons on other side. number of carbons between bridgehead carbons] ___-ane (total number of carbons)

bridgehead carbons

2 non-adjacent carbon atoms that belong to both rings in a bicyclic ring system

isomer

same molecular formula, different chemical structure