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150 Cards in this Set
- Front
- Back
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What are the most common Elements in organic chemistry? (composing 99% of the atoms in your body)
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H, C, N, O
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'Bonding' is defined as...
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The joining of 2 atoms in a stable state.
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What do atoms attain by bonding?
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a stable noble gas configuaration of electrons.
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How many electrons can hydrogen accommodate around it?
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2
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When is a second row element most stable? And what rule is an element said to be following when under these cirumstances?
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When it has 8 electrons around it, in accordance with the 'octet rule'
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Ionic bonds occur when...
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electrons are TRANSFERED from one element to another
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Covalent bonds occur when...
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2 elements SHARE electrons between their nuclei
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What does electronegativity measure?
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The strength of an atoms attraction for electrons in a bond. (The affinity that an atom has to form bonds in order to gain electrons.)
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explain the pattern of electronegativity on the periodic table
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Electronegativity increases across a row and increases up a column.
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The type of bonding that occurs between elements (ionic/covalent) is determined by what?
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an elements position on the periodic table.
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Under what conditions do ionic bonds generally occur?
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An ionic bond generally occurs when elements on the FAR LEFT side of the periodic table combine with elements on the FAR RIGHT side of the periodic table. (Between elements that are far away from each other on the p. table) (BIG DIFFERENCES BTWN ELECTRONEGATIVITIES)
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Under what conditions do covalent bonds typically occur?
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Covalent bonds typically form between elements in the middle of the periodic table.(such as Carbon) who would otherwise have to gain or lose several e-s to form an ion with a complete valence shell. (SIMILAR ELECTRONEGATIVITES)
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A compound with COVALENT bonds is called what?
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A molecule
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(1._____) may have either (2.____) or covalent bonds. (3.______) have ONLY covalent bonds.
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1. Compounds
2. Ionic 3. Molecules |
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The higher the difference is in two bound elements electronegativity, the ....
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stronger the ionic bond
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what element has the highest electronegativity?
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fluorine (i.e. non stick pans)
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How many carbon compounds exist?
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~3 million (and counting!)
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What are the steps in writing Lewis structures?
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i) calculate total number of valence e- for ALL of the atoms
ii) use pairs of e- to form bonds between all atoms that are bonded to each other iii) add remaining e- to give H a duet and every other element an octet |
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What are 'formal charges' used to show?
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formal charges are used to show charges on SOME atoms in molecules and ions.
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what's the formula for calculating formal charge?
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F.C.= [# of valence e-] - [# of e- an atom ''owns'']
(number of valence electrons minus the number of electrons that the atom owns) |
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How do you find out the # of electrons an atom "owns?''
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the number of electrons an atom owns = the number of unshared electrons + (the number of shared electrons divided by 2)
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Describe briefly the theory of resonance
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resonance structures are used to describe molecules and ions for which a single lewis structure is inadequate.
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What are Lewis structures?
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Lewis structures are dot representations for molecules.
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What are the rules in drawing Lewis structures?
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i) draw only valence electrons
ii) give every second row element an octet of electrons and hydrogen a duet. |
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when calculating total number of valence electrons what must you account for?
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any additional charges that may be on an ion (ex: CO3 has a negative charge of 2, so you have to ADD two electrons)
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How can you convert one resonance structure to another?
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by changing the position of electrons only.
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what kind of arrow is used to show movement of electron pairs?
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a curved arrow
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what do double headed arrows indicate?
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resonance
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in regard to resonance theory, what is a hybrid?
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a hybrid is the best representation of an ion out of all possible resonance structures. (the average of all the resonance structures)
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are resonance structures real?
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no, they exist only on paper.
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how can you tell how many valence electrons an element has?
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the number of valence electrons is equal to the group number of the element.
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What are isomers?
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different molecules with the same chemical formula (have same FORMULA, but look completely different--have different structure and properties! )
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what are constitutional isomers?
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isomers that have the same molecular formula but differ in the connectivity of their atoms
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What's the difference between isomers and resonance??
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resonance- only move electrons!!
isomers- can move both electrons AND nuclei (actual atoms themselves) |
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What is an orbital?
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a region of space where probability of finding electrons is high
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is energy greatest at the lowest of highest orbital...?
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highest. energy increases outwards/upwards from the nucleus.
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what shape are 's' orbitals?
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spherical
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what is a 'node' of electron density?
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a region of ZERO electron density
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what shape are 'p' orbitals?
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dumbbell shaped - tear drops
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what's the difference between atomic and molecular orbitals?
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atomic orbitals represent ATOMS.(Ex: Carbon) molecular orbitals represent molecules. (Methane)
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when/why do molecular orbitals form?
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when atomic orbitals overlap, molecular orbitals are produced.
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list the three HYBRID-atomic orbitals:
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sp, sp2, sp3
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what is hybridization...?
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the mixing of 's' and 'p' orbitals
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how do the energies of the sp3 hybrid orbitals compare to the energies of 2s and 2p unhybridized orbitals?
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the hybrid orbitals are INTERMEDIATE in energy between the energies of the unhybridized 2s and 2p orbitals
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sp3 hybrid orbitals take on what shape?
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tetrahedral (the 4 orbitals are now mutually repulsive-tetrahedral allows the four orbitals to be as far apart as possible)
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what is the measure of a tetrahedral angle??
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109.5 degrees
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sigma bond are ______. in regard to their symmetry.
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cylindrically symmetrical
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What kind of hybridization occurs when Carbon is bonded to 4 atoms?
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sp3
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Do you always get the same # of hybrid orbitals as the # of unhybridized atomic orbitals that are mixed?
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YES (so, one 2s and three 2p orbitals mix to yield FOUR sp3 orbitals!)
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what kind of hybridization occurs when Carbon is bonded to 3 atoms?
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sp2
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are sigma or pi bonds stronger..?
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sigma
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When Carbon is bonded to 2 atoms, what kind of hybridization occurs?
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sp
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for two hyrbidized sp orbitals to be as far apart as possible, by what degree are they separated from one another?
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180 degrees, they're positioned in a linear manor.
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[sp3, sp2, sp ] these hybrid orbitals are in the order of what regarding bond length....?
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[sp3, sp2, sp] is the order of GREATEST to LEAST bond lengths. (sp3 has the highest bond length, sp has the lowest---held closer together!!)
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what does it mean if an orbital used to form a bond has a high % s character?
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the higher the % s character, the stronger the bond
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which hybrid orbital forms the strongest bond based on %s character?
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sp - because sp orbitals have 50% s character
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Polar bonds result from what?
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unequal sharing of electrons in a covalent bond
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what is a dipole?
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dipoles occur in polar molecules. dipoles result from the more electronegative species "pulling" the negative charge (electron) towards themselves.
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will the atom with the higher percent s character will pull more of the electron density towards it, creating a dipole?
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yes
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what is a bronsted-lowry acid?
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a proton donor
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what is a bronsted-lowry base?
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a proton acceptor
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what do all bronsted-lowry acids have?
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a proton = Hydrogen (H)
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what do all BL bases have?
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either a lone pair OR a pi-bond
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what is a lewis acid?
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an electron pair acceptor
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what is a lewis base?
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an electron pair donor
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what do all lewis bases have?
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a lone pair or a pi-bond
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what do all lewis acids have?
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a proton (H) OR an unfilled valence shell or a partial charge (+)
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A bronsted-lowry acid does what?
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donates a proton to a bronsted-lowry base
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in bronsted-lowry reaction the conjugate base has ....
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one less H
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in a bronsted lowry reaction the conjugate acid has...
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one more H
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A lewis base does what?
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donates an electron pair to a lewis acid
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a lewis acid is also called a what?
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electrophile
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a lewis base is also called a what?
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nucleophile
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are all bronsted-lowry bases lewis bases?
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YES
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are all BL acids lewis acids?
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YES
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are all lewis acids BL acids?
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NO. not always...
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in BL reactions loss of a proton from an acid forms it's what?
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conjugate base (which will have one less H)
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in BL reactions gain of a proton by a base forms it's ....
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conjugate acid (which will have one more H)
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the more readily a compound donates a proton then the...
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stronger the acid is.
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the smaller the Pka the...
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stronger the acid
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the bigger the Ka the....
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stronger the acid
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what kind of relationship exists between acidity and basicity?
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and inverse one.
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a strong acid and a strong base form a ....
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weak acid and weak base!
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an acid can be deprotonated by the conjugate base of ...
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any acid having a HIGHER pka
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in proton transfer reactions (BL acid-base rxns) equilibrium favors what?
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the weaker acid and weaker base (the side with the LARGER pka)
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what are the four factors that can affect the acidity of H-A??
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1) elemental effects
2) inductive effects 3) resonance effects 4) hybridization effects |
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what is THE most important factor in determining the acidity of H-A is what?
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elemental effects (the location of "A" on the periodic table)
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The acidity of H-A increases across a row and ....
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DOWN a column
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acidity increases across a row just like what other characteristic?
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electronegativity
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acidity and electronegativity have what kind of relationship on the p table?
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inverse. electronegativity increases UP a column, whereas acidity and SIZE increase down a column.
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why is the size important in determining acidity?
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because the bigger the atom the more the charge can be spread out! (which stabilizes the charge and any time charge is stabilized acidity is higher!)
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what is the most important aspect of inductive effects in determining acidity?
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the electronegativity of "A"
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what IS an inductive effect??
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the pull of electron density through sigma bonds caused by electronegativity differences of atoms (E pulled toward more electronegative atom)
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what effect does the presence of electron-withdrawling groups have on acidity? (inductive effect)
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the more electronegative "A" is and the more pull there is the more spread out and stabilized the charge is and the more ACIDIC the compound is
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why does the presence of resonance effect acidity of a compound?
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because without resonance the charge is localized on one atom. and whenever the charge can be spread out, (de-localized through resonance)the more stable it becomes, and the more acidic a compound is.
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when the conjugate base of A is resonance stabilized....
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the acidity increases!
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how does hybridization effect acidity of H-A?
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% s character
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what is the correlation between %s character and acidity?
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increasing %s character, increasing acidity. (the higher %s, the closer the the lone pair is held to the nucleus and the more stable the conj. base)
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which is more acidic: sp, sp2 or sp3?
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sp! because it has the highest %s character (50%) sp3 is the weakest acid. (25%s)
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are sites on a molecule with pi bonds or lone pairs are basic or acidic?
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basic
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over right and down on the p table shows what?
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acidity (size increases down)
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over right and up on the p table shows what?
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electronegativity
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more electronegative groups stabilize the conjugate base making the acid what?
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stronger
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the more electronegative groups the more...
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acidic
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what do you do to draw the conjugate acid of a BL base?
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add a proton (H) to the base
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what do you do the draw the conjugate base of a BL acid?
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remove a proton (H) from the acid.
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in BL reactions protons are transfered from the
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acid to the base
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in BL reactions the eq lies to the side with the higher or lower pka?
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higher pka (weaker acid)
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what are the three types of intermolecular forces in order of strength? weakest-strongest
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1)van der waals
2)dipole-dipole 3)hydrogen (strongest) |
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what type of molecules exhibit van der waals forces?
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ALL molecules
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what type of molecules exhibit dipole-dipole forces?
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molecules with net dipole
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what type of molecules exhibit hydrogen bonding?
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molecules with an O-H, N-H, or H-F bond
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what is polarizability?
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a measure of how the electron cloud around an atom responds to changes in its electronic environment.
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what causes the very weak VDW forces?
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momentary changes in electron density in a molecule.
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what are the only attractive forces present in nonpolar compounds?
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van der waals forces
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weak interaction of temporary dipoles constitutes what forces?
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van der waals forces
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what determines the strength of VDW forces?
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the amount of surface area. the larger the surface area, the larger the attractive force between two molecules and the stronger the intermolecular forces.
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what are the two factors that affect strength of VDW forces?
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1)surface area
2)polarizability |
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are larger or smaller atoms more polarizable?
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larger! larger atoms have more loosely held valence electrons and are therefor more polarizable than small ones with tightly held electrons.
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what are dipole dipole interactions?
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the attractive forces between the permanent dipoles of two polar molecules
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the dipoles in adjacent molecules align how?
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so that the partial negative and partial positive are in close proximity.
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what is the relationship between boiling point and intermolecular forces?
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the stronger the intermolecular forces, the higher the boiling point.
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what effect does the surface area have on boiling point?
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the larger the surface area, the higher the boiling point
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what effect does polarizability have on boiling point?
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the polarizable an atom, the higher the boiling point.
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what effect does the strength of intermolecular forces have on melting point?
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the stronger the intermolecular forces, the higher the melting point
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what effect does the symmetry of a compound have on the melting point?
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given the same functional group, the more symmetrical the compound, the higher the melting point.
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compounds tend to dissolve in solvents that have what kinds of intermolecular forces relative to their own?
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"like dissolves like." compounds dissolve in solvents having similar kinds of intermolecular forces.
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what do polar compounds dissolve in?
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polar solvents
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what do nonpolar compounds dissolve in?
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nonpolar solvents.
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what kind of solvents do ionic compounds need to dissolve?
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very polar solvents
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most ionic compounds are soluble in _____ but insoluble in _______.
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most ionic compounds are soluble in water but insoluble in organic solvents.
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an organic compound (usually soluble in organic solvents) may be water soluble under what condition?
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if it contains one polar functional group (that is capable of hydrogen bonding with the solvent) for every 5 Carbon atoms it contains (1:5)
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a water soluble organic compound contains what?
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an O- or N-containing functional group that solubilizes its nonpolar carbon backbone.
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the nonpolar part of a molecule that is not attracted to water is said to be what?
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hydrophobic
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the polar part of the molecule that can hydrogen bond to water is said to be what?
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hydrophilic
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is the hydroxy group (cooh) hydrophobic or philic?
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hydrophillic
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usually a polar bond will have an EN difference of what?
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.5 units between the two atoms
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a carbon-carbon bond and C-H bond are considered to be what regarding polarity?
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nonpolar
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polar molecules posses what kind of intermolecular forces?
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dipole dipole
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hydrophobic portions of a compound will be primarily
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hydrocarbon chains
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hydrophillic portions of a compound will typically be
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polar
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how can an organic molecule be water soluble?
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have N or O polar bond per 5 carbon!
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what are the steps in determining acidity?
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1. elemental effects, inductive, resonance, hybridization
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how do you know if a molecule can h bond with itself??
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must have NOF-H bond!!
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how do you know if a molecule can only h bond with water??
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it just has NOF
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when determining bp and mp what constitutes an h bond?
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must have H-NOF (if just polar atom then it's DD bonding!)
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atomic number = number of protons=
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number of elctrons!!
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whats the acronym for 3 groups of functions groups?
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c-z group : AAEATS
c=o group: AKCEAA |
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an EN heteroatom makes carbon a nucleophile or electrophile?
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electrophile!
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lone pair or pi bonds make a nucleophile or electrophile?
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nucleophile! (basic)
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