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Organic Chem I > Ch2 > Flashcards

Ch2 Flashcards

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1
Q

Alkanes and cycloalkanes are

A

Saturated Hydrocarbons that only have single bonds

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2
Q

Alkanes and cycloalkanes are ___ - hybridized with what degree?

A

Sp^3 and 109.5

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3
Q

What is the first step in naming alkanes?

A

Finding the longest parent chain

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4
Q

When naming alkanes, what does the prefix indicate and what are the first 10?

A 
# of carbons
Meth-1
Eth-2
Prop-3
But-4
Pent-5
Hex-6
Hept-7
Oct-8
Non-9
Dec-10
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5
Q

Where are substituents located?

A

They branch from the parent chain

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6
Q

When numbering alkanes, where should you start?

A

At the end closest to a substituent to give it the lowest possible number

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7
Q

If there are mutltiple substituents what should you do?

A

Number the parent to give lowest numer to substituent closest to an end then list substituents in alphabetical order

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8
Q

If there are identical subsitituents

A

The prefix di, tri, and tetra are not considered in alphabetizing

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9
Q

Memorize isopropyl, isobutyl, sec-butyl, tert-butyl, amd neopentyl

A

**when alphabetizing, ignore hyphenated prefixes sec- and ter-

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10
Q

Assume C is binded to _ unless anither substituent is labeled

A

H

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11
Q

1 C is bonded to how many C’s an H’s?
2 C?
3 C?
4 C?

A

1 carbon and 3 primary H’s
2 Cs and 2 secondary Hs
3 Cs and 1 tertiary H
4 Cs and no Hs

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12
Q

How does the nomenclature for cycloalkane work?

A

Put cyclo before alkane root

If 2 substituents, #1 goes to group that comes first alphabetically

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13
Q

What are bicycloalkanes?

A

Alkanes with two rings that have carbons in common

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14
Q

What are bridgehead carbons

A

The carbon atoms shared by all two-ring sets

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15
Q

In bicycloalkanes, the # of carbons in the parent are the two bridgehead carbons plus

A

All of the bridging carbons

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16
Q

Bridge lengths go in ____ in ____ order

A

Brackets []

Descending

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17
Q

Given a choice, give lower numbers to___ or ____

A

Functional groups or substituents

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18
Q

General IUPAC rules

A

Parent: prefix-infix-suffix
Prefix: # of C atoms
Infix: type of C-C [an: C-C bonds; en: ≥1 C=C bond; yn: ≥1 C triple bond C
Suffix: functional group

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19
Q

Suffix functional groups

A
  • e: hydrocarbon (R-H)
  • ol: alcohol (R-OH)
  • al: aldehyde (R-CH=O)
  • amine: amine (RR’R”N)
  • one: ketone (R-C(=O)-R’)
  • oic acid: carboxylic acid (R-C(=O)-OH)
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20
Q

Eclipsed ethane is _ energy / _ stable than staggered ethane because of

A

Higher
Less
Torsional strain

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21
Q

Torisonsl strain is also known as and is?

A

Bonded strain

The energetic cost of the repulsion of the electrons in eclipsed bonds

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22
Q

In butane, the methyl groups move _ each other as you rotate 60°

A

Away

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23
Q

If not anti, it must be

A

Gauche

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24
Q

Non-bonded strain=

A

Steric strain

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25
Q

What is strain?

A

The increase in the pe of a molecule due to the deviation in its structure from ideal values

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26
Q

Components of strain in molecules

A 
Angle strain
Torsional strain
Non-bonded strain
Bond strain
Coulumbic strain
27
Q

Angle strain

A

Compression or expansion of a bond angle

28
Q

Torsional strain

A

When bonds are not staggered

29
Q

Non-bonded strain

A

When two remote groups approach too closely (usually destabilizing, sometimes stabilized); ex:gauche

30
Q

Bond strain

A

Compression or stretching of bonds

31
Q

Coulumbic strain

A

Stabilizing or destabilizing

32
Q

Cyclopropane has 28 kcal/mol of strain due to

A

Angle strain: the C-C-C bond angles are compressed from 109.5° to 60°
Torsional strain: there are 6 sets of eclipsed hydrogen interactions with H-C-C-H = 0°

33
Q

Cyclobutane has _ kcal/mol of strain

Cyclopentane has _ kcal/mol of strain

A

26

6.5

34
Q

Planar cyclobutane and cyclopentane try to reduce _ strain but this increases _ strain (a trade-off)

A

Torsional

Angle

35
Q

In cyclobutane, the best compromise has C-C-C = ___ and H-C-C-H = ___

A

88°

24°

36
Q

The two chair conformations in cyclohexane

A

Have no angle or torsional strain

  • C-C-C Angles are ideal: 109.5°
  • all bonds are staggered
37
Q

Boat conformation for cyclohexane

A

6.5 kcal/mol strain vs. chair conformer
Nonbonded strain due to flagpole interactions
Eclipsed across two C-C bonds

38
Q

Twist-boat conformation for cyclohexane

A

5.5 kcal/mol strain vs. chair conformation
Nonbonded strain is greatly reduced vs. boat
Some torsion strain from partially eclipsed C-H bonds

39
Q

How many gauche interactions does the axial methyl group have in Methylcyclohexane? What about the equatorial conformation?

A

Axial methyl has gauche interactions and equatorial conformation has no gauche interactions

40
Q

Cis-isomers:

Trans-isomers:

A

Cis- both groups are on same side of ring

Trans- groups are on opposite sides of the ring

41
Q

Cis- trans isomers are ___ isomers; possible in ___ and ___; and have the same ___ and ___ but are ___

A

Geometrical
Rings and alkenes
Molecular formula and atom connectivity
Not interconverted via rotation about single bonds

42
Q

Bp of methane, butane, pentane, decane?

A

Methane = - 164°c
Butane = 0°c
Pentane = 36°c
Decane =174°c

43
Q 
Intermolecular attractive forces….
Ion/ion =
Dipole/dipole=
H-bonds =
Ion/dipole =
A

Very strong
Very weak
Moderate
Strong

44
Q

London dispersion forces are ____ that depend on

A

Instantaneous dipole/induced dipole

The total contact surface area between molecules

45
Q

Two limiting cases when comparing two molecules (London dispersion forces)

A

If the shapes are the same, then the forces increase as the number of atoms increases

If the number of carbons is the same, then the forces decrease with increased branching

46
Q

Chrial centers have to have __ different substituents

A

4

47
Q

Objects that are not superimposable on their mirror images are __ and show handedness… they are different.

A

Chiral

48
Q

Objects that are superimposable on their mirror images are ___ and do not show handedness. An ___ object has at least one element of symmetry. They are the same

A

Achiral

49
Q

Plane of symmetry (mirror plane) is an

A

Imaginary plane through an object where one half is the mirror image of the other half

50
Q

Center of symmetry at the atom (x,y,z) is

A

The exact same as the atom at (-x,-y,-z) for all atoms in the molecule (inversion center)

51
Q

A tetrahedral atom bonded to four different groups is

A

A chiral (asymmetric) center

52
Q

A stereocenter is an atom where

A

The interchange of two groups gives a atereoisomer of the original molecule

53
Q

A carbon bonded to H, CH3, I and Cl is

A

A chiral center amd stereocenter

54
Q

All chiral centers are

A

Stereocenters but all stereocenters are not chiral

55
Q

When it comes to R and S, the higher the atomic number, the ….. and if it cannot be assigned using the atoms bonded to the chiral center, use

A

Higher the priority… the next set of atoms

56
Q

When naming enantiomers…

A
  1. ) locate the chiral center
  2. ) prioritize each substituent from 1-4
  3. ) draw an arc from 1-3
  4. ) CW= R, CCW= S
  5. ) but if lowest priority isn’t on dash, switch R or S
57
Q

How do you figure out how many stereoisomers a molecule has?

A

2^(# of chiral centers)

58
Q

With meso compounds, the mirror place is ____; therefore

A

The exact same; not an enantiomer

59
Q

What are Meso compounds and what must they have?

A

An achiral compound possessing two or more chiral centers that must have an internal mirror plane of symmetry or an inversion center

60
Q

Enantiomers have ___ physical and chemical properties while diastereomers have ____ physical and chemical properties

A

Identical

Different

61
Q

Enantioners become ___ in a chiral environment

A

Diastereomeric

62
Q

In Fischer projections, vertical bonds ____ while horizontal bonds ____

A

Vertical: bonds projecting away from you
Horizontal: bonds projecting toward you

63
Q

There is angle strain whenever

A

An angle is less than 109.5 degrees

64
Q

Gauche interactions occur

A

Whenever 2 non-hydrogen molecules are 60 degrees away from each other

Organic Chem I (1 decks)

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