Ochem Flashcards
Hybridization
-a way of making all of the bonds to a central atom equivalent to each other
-sp3 = tetrahedral (hallmark of carbon containing molecules, one s and 3 p-orbitals)
-sp2 = trigonal planar geometry (one s orbital mixed w/ 2 p orbitals , the third p orbital is unhybridized and can be used to form a π bond), seen in alkenes
-sp = linear geometry ( to form a triple bond, 2 of the p orbitals form π bonds and the third p orbital will combine w/ the s orbital to form 2 sp orbitals)
Resonance
describes the delocalization of electrons in molecules that have conjugated bonds (when single and multiple bonds alternate)
Lewis acid
is an electron acceptor in the formation of a covalent bond, tend to be electrophiles
Lewis base
is an electron donor in the formation of a covalent bond, nucleophiles
Brønsted-Lowry acid
species that can donate a proton (H+)
Bronsted-Lowry base
a species that can accept a proton
Amphoteric
molecules like water that have the ability to act as either Bronsted-Lowry acids or bases
Acid dissociation constant, Ka
measures the strength of an acid in solution
Ka = [HA+][A-]/[HA]
pKa of acid
pKa = -logKa
Nucleophiles
“nucleus-loving” species with either lone pairs or π bonds that can form new bonds to electrophiles
–good nucleophiles tend to be good bases
In protic solvents, nucleophilicity decreases in the order
I- > Br- >Cl- > F-
In aprotic solvents, nucleophilicity decreases in the order
F- > Cl- > Br- > I-
Electrophiles
“electron-loving” species with a positive charge or positively polarized atom that accepts an electron pair when forming new bonds with a nucleophile
Leaving groups
the molecular fragments that retain the electrons after heterolysis
-weak bases make good leaving groups (I-, Br-, and Cli)
SN1 reaction
-contains two steps, the first step is the rate-limiting step
-1. the leaving group leaves, generating a positively charged carbocation. 2. The nucleophile attacks the carbocation, resulting in the substitution product
-the rate of the reaction only depends on the concentration of the substrate: rate = k[R-L]
-first order reaction; anything that accelerates the formation of the carbocation will increase the rate of this rxn
-product will usually be a racemic mixture
SN2 reaction
-contains only one step in which the nucleophile attacks the compound at the same time as the leaving group leaves
-concerted reaction
-the single rate-limiting step involves 2 molecules (the substrate & the nucleophile)
-the concentrations of the substrate and the nucleophile have a role in determining the rate: rate = k[Nu][R - L]
-the nucleophile actively displaces the leaving group in a backside attack
Nomenclature of Alcohols
-have the general formula ROH, with the functional group -OH referred to as a hydroxyl group
-names in the IUPAC by replacing the -e ending of the root alkane w/ -ol
-common naming practice is to name the alkyl group as a derivative followed by alcohol
-when the alcohol is not the highest-priority group, it is named as a substituent w/ the prefix hydroxy-
Phenols
-hydroxyl groups that can be attached to aromatic rings
-the hydroxyl hydrogens are acidic due to resonance within the phenol ring
-have higher melting and boiling points than other alcohols due to intermolecular hydrogen bonds
-more acidic than nonaromatic alcohol, so they can form salts w/ inorganic bases such as NaOH
-Ortho: two groups on adjacent carbons
-Meta: two groups separated by a carbon
-Para: two groups on opposite sides of the ring
Oxidation reactions of alcohols
-Primary alcohols can be oxidized to aldehydes, but only by pyridinium chlorochromate (PCC)— oxidation of primary alcohols w/ a strong oxidant like chromium (VI) will produce a carboxylic acid
-Secondary alcohols can be oxidized to ketones by PCC or any stronger oxidizing agent —- oxidation w/ a strong oxidizing agent can fully oxidize secondary alcohols to ketones
-Tertiary alcohols cannot be oxidized because they are already as oxidized as they can be w/o breaking a carbon-carbon bond
-Jones oxidation (CrO3 dissolved w/ dilute sulfuric acid in acetone) oxidizes primary alcohols to carboxylic acids and secondary alcohols to ketones
Reactions of Phenols (quinones and hydroxyquinones)
-treatment of phenols w/ oxidizing agents produces compounds called quinones –named by indicating the position of the carbonyls numerically and adding quinone to the name of the parent phenol —some do have aromatic rings but not always, serve as electron acceptors biochemically, specifically in the electron transport chain in both photosynthesis and aerobic respiration
-hydroxyquinones share the same ring and carbonyl backbone as quinones, but differ by the addition of one or more hydroxyl groups, many have biological activity and are used in the synthesis of medications
Reactions of Phenols (ubiquinone)
-an example of a biologically active quinone, also called coenzyme Q and is a vital electron carrier associated w/ complexes I, II, and III of the ETC
-the most oxidized form that this molecule takes physiologically: it can also be reduced to ubiquinol upon the acceptance of electrons —-this oxidation-reduction capacity allows the molecule to perform its physiological function of the electron transport
Tautomerization
movement of a hydrogen and a double bond
Micheal addition
the addition of an enolate to an electrophilic alkene, such as an α-β unsaturated ketone, nitrile, or ester
Imine
a compound that contains a C-N double bond