OChem 261 Midterm One

methyl group

CH3 group off a compound

methylene group

CH2 bound to 2 other things

steps to determine empirical formula

1. divide all % by each atomic mass
2. divide each by smallest value calculated
3. adjust for whole number ratios

double bond equivalents

use to find number of possible double bonds of a compound

1-N+0.5(sum of ni vi)

ionic bonding

transfer of electrons and charges

covalent bond

sharing of electrons

single bond hybridization

four sp3 hybrid orbitals

109\.5 degree angles

alkanes

double bond hybridization

three sp2 orbitals and one p orbital

120 degree angles

alkenes

triple bond hybridization

two sp orbitals and two p orbitals

180 degree angles

alkynes

sigma and pi overlap

ex. acetylene

saturated compound

contains the maximum amount of hydrogens each carbon can possess

single bond compounds are saturated

alkyl

formed by removing a hydrogen from an alkane

H---R

phenyl

benzene ring attached to another molecule

alkyl halides

hydrogen replaced by a halogen in an alkane

R-----X (fluorine, chlorine, bromine, iodine)

primary when C attached to R and one C atom

secondary when C atom attached to R and two C atoms

tertiary when C attached to R and three C atoms

alcohols

OH ----- sp3 hybrid C

can be primary, secondary or tertiary

phenol

hydroxyl OH group bonded to benzene ring

ether

R--O--R’ or R-O-R

derivative of water where both H replaced by alkyl groups

name alkyl groups alphabetically and numeric prefixes + ether

amines

R--NH2

derivatives of ammonia where H is replaced by alkyl group

primary: one H replaced

secondary: two H replaced

tertiary: three H replaced

aldehydes

carbonyl group (C=O) bonded to H

R-C=O-H

ketones

carbonyl group bonded to two C atoms

R-C=O-R’

carboxylic acids

carboxyl group joined to alkyl

R-C=O-O-H

esters

carbonyl group bonded to alkoxyl group (alkyl + O)

R-C=O-O-R

amides

carbonyl bonded to nitrogen bearing hydrogen/alkyl groups

R-C=O-NH2 or R-C=O-NH-R’ or R-C=O-N-R’-R”

primary: amino group directly bonded to one carbon

secondary: amino group bonded to two carbons

tertiary: amino group bonded to three carbons

nitriles

R-C=-N (triple bond sp hybrid between C and N)

how to calculate formal charge

total number valence e - (half shared + all unshared)

resonance structures

not real

can only move electrons

valence rules must be fulfilled

resonance stabilization

more stable resonance structure = more contribution to hybrid

can have negative charge on electroneg atom

what makes stable resonance structures?

more covalent bonds in resonance

all atoms having complete valence shell

no charge separation

wave number

position of absorption band in IR spectrum

reciprocal of wavelength

larger number = higher frequency of wave

covalent bond vibrations

stretching and bending

factors affecting frequency

masses of bonded atoms and stiffness of bond

multiple bonds are stiffer, requiring more energy to stretch, so triple bonds have a higher frequency than double bonds

light atoms higher frequency than heavier

radical

intermediate possessing unpaired electron

radical reaction

each atom takes one electron from the covalent bond that joined them

naming rules for alkyl group

regular alkane name but ad -yl for compounds missing an H

naming branched chain alkanes

1. locate longest chain
2. name according to number of carbons
3. number in a way such that the substituent is closest to 1
4. designate location of sub group (list alphabetically)


1. use di, tri etc. for subs that are the same

physical properties of hydrocarbons

don’t react with oxygen at room temperature

stability of radicals

tertiary are most stable, primary are least

multiple halogen substitution

when alkane not in excess

each time a substitution of Cl for H takes place, a molecule of H-Cl is formed

dichloromethane forms, and then tri and then tetra (all H become replace by Cl)

secondary radical

radical carbon is attached to two other carbons

chlorination

replacing H in H-R with Cl

Initiation: rxn promoted by heat/light and each Cl in Cl2 takes one Be, forming 2 Cl radicals

propagation: A. a Cl ion grabs a H from methane, producing HCl and methyl radical B. methyl radical abstracts a Cl from Cl2, forming chloromethane and a Cl atom (repeat A)

termination: any two radicals coupling up

bromination

initiation: Br abstracts H in H-R to form H-Br and R radical

propagation: R radical abstracts Br from Br2 to form R-Br and Br radical

termination: and two radicals coupling up

selectivity of bromine

chooses where most stable radical intermediate can be formed

Br more selective than Cl bc not as reactive

hydrogenation

converts multiple bonds to single bonds by the addition of H atoms

occurs at room temp with catalyst (Pt or Pd)

H atoms added to ends of same face (syn addition)

alkynes will need 2 H2

steroid backbone

four rings:

three cyclohexanes fused to one cyclopentane

Four motion types in IR spectroscopy

stretching and bending

scissoring and rocking

kolbe electrolysis

acetic acid + Na (bc electrolysis)

bond bw R and C is broken bc e- transfer to C-O bond

products: methyl radical and carbon dioxide

reverse hydrogenation

alkyl halide + hydrogen ION form alkane

Grignard reagents

alkyl halide + Mg (ether solution) → R-Mg+X

conformation

different arrangement in space that results from the rotation about single bonds

staggered conformation

lowest energy (most stable)

atoms bonded to each carbon are as far apart as possible

eclipsed conformation

highest energy bc large molecules close together

atoms bonded to carbons cover each other

2 eclipse conformations bc rotation (bigger molecules closer together = more unstable)

gauche conformation

similar to staggered but R group has moved closer to other R group therefor higher energy than staggered

chair conformation

most stable form of cyclohexane because no angle or torsional strain

all C-C angles 109.5

when flipped, all axial atoms become equatorial and vice-versa

boat conformation

less stable than chair because torsional strain

\

axial bonds\`

up and down

equatorial bonds

are at an angle

if one substrate on compound, equatorial conformation is favoured

Exponentially more equatorial than axial

trans cyclohexane

one group attached by an upper bond and one by a lower bond

cis cyclohexane

both groups attached by upper or both attached by lower

first elements on periodic table

HHELIBEBCNOFNENAMGALSIPSCLAR

Here He Lies Beneath Bed Clothes, Nothing On, Feeling Nervous, Naughty Margret Always Sighs, ” Please Stop Clowning Around ”

propyl group

\-CH2CH3CH3

ethyl group

\-CH2CH3