Chapter 1: Bonding In Organic Compounds Flashcards
Organic Chemistry
of structure, properties and reactions of organic materials (matter that contains carbon atoms)
how are carbon atoms linked in organic compounds
one or more atoms of carbon are covalently linked to atoms of other elements
what are the most common atoms of other elements that carbon is linked to in organic compounds
- hydrogen
- oxygen
- nitrogen
what are not organic compounds
carbides, carbonates and cyanides
in 1828, who discovered another way that urea can be produced
Freidrich Wohler discovered that urea can be produced from inorganic compounds
how is each orbital characterized
by a unique set of quantum numbers
principal quantum number (n)
a whole number that specifies the electron shell and it related to the energy of the orbital
angular momentum quantum number (s,p,d,f)
describes the shape of the orbital
spin quantum number
the spin of an electron, it will be +1/2 or -1/2
what is the angular momentum quantum number of carbon
1s^2,2s^2,2p^2
what is the probability of finding an electron in the s orbital
this is where the probability is high, 90-95%
shape of s orbitals?
spherically symmetric
shape of p orbitals?
like dumbells
for what n numbers are p orbitals possible and not possible
not possible for n=1, but are possible for n=2 and higher
when n is greater than one, how many p orbitals are there per n value
there are 3 p orbitals for every value of n
octet rule
maximum stability results when an atom is isoelectronic with a noble gas, aka has 8 electrons in its valence shell (same as noble gases)
what is it called when an electron pair is shared between 2 atoms
a covalent bond
when is the octet rule most useful
in cases involving covalent bonds to Carbon, nitrogen, oxygen and fluorine (CNOF)
what is another name for a double bond
a pi bond
what is electronegativity
a measure of the ability of an element to attract electrons towards itself when bonded to another element
an electronegative element attracts electrons
who made the electronegativity scale and what is it
Pauline made the scale and it goes from 0-4
what is the most electronegative element
fluorine (F) (4)
how does a polar covalent bond happen
it is when atoms share electrons in their bond still, but not equally
relationship between electronegativity and polarity of a bond
the greater the difference in electronegativity, the more polar the bond
what is a dipole moment a measure of
it is a measure of the polarity of a bond, so more polar bonds mean a higher dipole moment
give an example of dipole moment and polarity using fluorine
since fluorine is the most electronegative, it will have the most polarity in a bond, and will therefore have the highest dipole moment
what is formal charge
the charge calculated for an atom in a lewis structure
what is the net charge
the sum of the formal charges
what does the formal charge correspond to the difference of
the difference between the number of valence electrons an atom has in the neutral free atom and the valence electron count for a covalently bonded atom
formal charge is shown as…
a + or - on a diagram
what is connectivity/constitution
the order in which the atoms of a molecule are connected
why is the constitution important in terms of lewis structure
they are necesary to write a lewis structure
what are isomers
different compounds that have the same molecular formula
what are constitutional isomers
isomers that differ in the order in which atoms are connected
what is another name for constitutional isomers
structural isomers
what is a condensed formula
it is abbreviated from the lewis structure and lists the groups of atoms in order
ex)
CH3CH2NH2
can 2 or more lewis structures be written for certain compounds or ions?
yes
when are lewis structures called resonance structures?
when they have the same connectivity of atoms and the same number of electrons and the same net charge
what is a resonance hybrid
when molecules exist as an average of the resonance structures
is just the average of the resonance structures
what is the relationship between resonance and stability
the more resonance, the more stable, because it can’t move as much and there is more structure
8 Rules for Resonance Structures
- the atom connectivity must be the same (atoms can’t just totally move)
- Each must have the same number of electrons and the same net charge
- Must have the same number of unpaired electrons (dots in lewis structure)
- Second row elements (ex. N) must not have more than 8 valence electrons (can’t have 10, for example)
- The structure with the most bonding electron pairs is the most important ( for its chemical properties) (so double bond over single bond)
- The structure with the lower amount of charged atoms is more important
- The negative charge should be on the most electronegative atom and the positive charge should be on the least electronegative atom
- Resonance structures show electron delocalization and this electron delocalization stabilizes molecules. Resonance stabilization is highest if the resonance structures are equally stable
3 main reasons why resonance structures are so important
- resonance structures and resonance hybrids better represent delocalization of electrons between atoms
- resonance structures help understand reactivity
- molecules or ions in which the electrons are delocalized are unusually stable
relationship between NG and stability
the higher the NG content, the less stable
when rxns form unstable products…
the reaction takes longer
what is the most stable arrangement of groups attached to a central atom
when there is maximum separation (so the degree angle) between electron pairs
in molecules such as water, what determines the overall shape (for example, bent)
the nonbonding electron pairs
is valence shell electron repulsions more or less for bonded electron pairs
bonded electron pairs have less repulsion than nonbonded electron pairs, because they are kinda stuck together
linear arrangement special rule
4 electron double bonds and 6 electron triple bonds are considered one group of electrons in terms of spatial requirements and therefore are linear. an example of this is carbon dioxide
what is a dipole moment of a molecule
the sum of the individual dipoles, which happen when there are polar bonds
what happens if the dipoles cancel (arrows go in opposite directions)
the net dipole moment is zero (this is the only time that the dipole is zero)
how are reactivity and properties of molecules determined
by their strength and polarity
STRUCTURE = FUNCTION
what are curved arrows used for
to track the flow of electrons in chemical reactions
how to the curved arrows work
the arrow begins where the electrons were originally and points to where they end up
what do X’s mean
halogens
multiple curves arrows
can show how a reaction progresses, for example they can show a proton transfer reaction. can also show the movement of bonding electron pairs
IN THE PRESENCE OF ACID
H2O CAN BE PROTONATED
a bronsted acid is a
proton donor
a bronsted base is a
proton acceptor
in an acid base reaction, a proton is transferred from the…
acid to the base
proton donor => proton acceptor
what are the acids and bases converted to in an acid-base reaction
a conjugate acid and conjugate base
strong acids have _______ Ka’s and _______ pKa’s
high, low
the stronger the acid, the ____________ its conjugate base
weaker
what are the major factors that affect the acidity (3)
- strength of the bond to hydrogen
- electronegativity of the atoms from which the proton is lost
- electron delocalization in the conjugate base
what happens to the bond to the hydrogen as the halogen size increases
the bond to the hydrogen becomes weaker
charge on the conjugate base is more spread out with the larger halide anions
why does electronegativity increase across the periodic table
the increased polarity of the bond to hydrogen increases the partial charge on the hydrogen which increases the electronegativity
what is the relationship between electronegativity and acidity
electronegative elements can influence acidity by the inductive effect. The electron withdrawing effect increases the partial positive charge and stabilizes the conjugate base
what happens to the acid when the conjugate base is stabilized by electron delocalization
the acid is stronger
what type of acid and base does equilibrium favor in an acid-base reaction
equilibrium favors the weaker acid and weaker base
how do you calculate the equilibrium constant
Ka of reactant acid/Ka of product acid
how can you predict the direction of proton transfer
use the pKa’s
for example, the wekaer acid has a higher pKa, and so the higher pKa is favored at equilibrium
Lewis acid
electron pair acceptor
lewis base
electron pair donor
lewis acid-base reaction
a non bonding electron pair on the base bonds to the acid. the acid and base may or may not have a formal charge
what is the lewis acid base idea also relevant to
substitution reactions and bronsted lowry proton transfer reactions
