ochem exam 1

how many isotopes does carbon exist as

three

what is an isotope

an element with the same atomic number but a different atomic mass

are noble gases reactive or nonreactive? why?

nonreactive because they have full valence electron shells, making it hard for them to gain or lose electrons

how does carbon reach an unreactive closed shell

by sharing electrons, i.e. forming chemical bonds

tetravalent

when an atom has four bonds to other atoms to fill its valence shell ex. Carbon

parts of a skeletal formula

each corner is a carbon atom

each connecting line is a C-C bond

triangle shape alkane

cyclopropane

square shaped alkane

cyclobutane

pentagon shaped alkane

cyclopentane

hexagon shaped alkane

cyclohexane

what makes carbon unique

it forms stable bonds with itself

electronegativity

a measure of the force of an atoms attraction for the electrons it shares in a chemical bond

eectronegativity periodic table trend

highest in the top right

polar covalent bond

atoms share electrons to fill their valence shells

a dipole is formed

H bonding in neutral molecules

one bond

C bonding in neutral molecules

four bonds

N bonding in neutral molecules

three bonds and one lone pair

O bonding in neutral molecules

two bonds and two lone pairs

Halogen (second to last column) bonding in neutral molecules

one bond and 3 lone pairs

4 groups bonded to carbon means

sp3 hybridization, 109.5 degree bond angle, four sigma bonds

3 groups bonded to carbon means

sp2 hybridization, 120 degree bond angle, three sigma bonds and one pi

2 groups bonded to carbon means

sp hybridization, 180 degree bond angle, two sigma bonds and two pi

sigma bond

a covalent bond in which orbitals overlap along the axis joining the two nuclei

pi bond

covalent bonds formed by the overlap of parallel p orbitals

which is stronger: pi or sigma bonds

sigma bonds

on a resonance structure, where do the curved arrows point

they originate from the electrons/bonds and point towards where they will move to in the resonance structure

resonance structure rules

same number of valence electrons

obey covalent bonding rules

same total number of paired and unpaired electrons

shape of an s orbital

a sphere

shape of a p orbital

two lobes arranged in a straight line with the center at the nucleus

functional groups

an atom or group of atoms within a molecule that shows a characteristic set of physical and chemical properties

arrhenius acid

dissolves in water to produce H⁺ ion

arrhenius base

dissolves in water to produce OH^- ions

bronsted lowry acid

proton donors

bronsted lowry base

proton acceptor

lewis acids

electron pair acceptor

lewis base

electron pair donor

weak acid

a substance that only partially dissociates in water to produce H₃O⁺ ions

weak base

a substance that only partially dissociates in water to produce OH^- ions

lower pKa value means

stronger acid

where does equilibrium lie in an acid base reaction

on the side of the weaker acid and weaker base

factors in determining acidity

the electronegativity of the anion bonded to H

resonance stabilization of the anion (more stable anion means stronger acid)

the inductive effect

the size and delocalization of the charge in the anion

hydrocarbon

a compound composed only of hydrogen and carbon

saturated hydrocarbon

only carbon and hydrogen single bonds

unsaturated hydrocarbon

a hydrocarbon containing double and/or triple bonds

general formula for alkanes

C_nH_2n+2

alkane shape

tetrahedral

109.5 degree bond angles

constitutional isomers

compounds with the same molecular formula but a different connectivity of their atoms

what does the suffix -ane signal

an alkane

substituent

a group bonded to the parent hydrocarbon chain

alkyl group

a hydrocarbon substituent

how do you classify a carbon as primary, secondary, tertiary, or quaternary

count how many other carbons its bonded to

conformation

any three-dimensional arrangement of atoms in a molecule that results from a rotation about a single bond

staggered conformation

when viewed through a newman projection, no carbons overlap

eclipsed conformation

when viewed through a newman projection, carbons overlap

which conformation is lower energy

staggered

torsional strain

strain occurring when a staggered conformation is forced to an eclipsed one

which conformation is most stable

chair conformation since all bonds are staggered

chair conformation

all bonds are staggered and 109.5 degrees

six bonds are equatorial and six are axial

boat conformation

puckered conformation where carbons 1 and 4 are bent towards each other

has torsional and steric strain

steric strain

created by one set of flagpole interactions

cis-trans isomers

have the same molecular formula but a different arrangement of atoms in space that cannot be interconverted by rotation about sigma bonds

what does a number out in front of a compound mean

the location (carbon #) that the substituent is attached to

methyl group

CH₃

single bond parts

one sigma bond

double bond parts

one sigma bond

one pi bond

triple bond parts

one sigma bond

two pi bonds

equatorial position

sticking outward on the same plane as the ring

axial position

up or down parallel to the imaginary axis running through the center of the ring

which position is more stable

equatorial position because of less strainin

inductive effect

when a partial charge is in close proximity to a highly charged atom, it delocalizes the charge of an ion which makes it more stable

what does greater electronegativity of the anion mean for the strength of the acid

acid will be stronger

what does greater resonance stabilization of the anion mean for the strength of the acid

acid will be stronger

what does a greater electronegativity difference mean for delocalization of charge

delocalization is enhanced

what does charge delocalization mean for pKa

pKa is lowered since the acid increases in strength

delocalization

the ability for a molecule or atom to spread out its electronic charge thus stabilizing it

why do resonance structures stabilize a molecule

charge is shared between multiple atoms between resonance structures instead of just one, which delocalizes it and increases the stability

what does the prefix -iso mean

all carbons except one form a continuous chain (forked end)