Important words and concepts from Chapter 4, Campbell & Reece, 2002 (1/14/2005):

by Stephen T. Abedon (abedon.1@osu.edu) for Biology 113 at the Ohio State University

 

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(1) Chapter title: Carbon and the Molecular Diversity of Life

(a)                    Found at this site are additional pages of possibly related interest including: [organic chemistry primer]

(b)                    External links include:

(i)                     [carbon and the molecular diversity of life (Google Search)]

(ii)                   [carbon-based compounds, functional groups, carbohydrates (Biology at Clermont College)

(2) Mechanistic basis of life

(a)                    First we reviewed chemistry, then we considered the chemical and physical properties of water, now we'll consider the chemistry of the complex stuff that floats around in the water found within living things.

(b)                    "Biological diversity reflects molecular diversity; and carbon, of all chemical elements, is unparalleled in its ability to form molecules that are large, complex, and diverse."

(c)                    The distinction between organic compounds and inorganic compounds was originally made on the basis of their origin, i.e., the former came from living things while that latter need not.

(d)                   Today we know that the distinction between made by living things and not necessarily made by living things is somewhat arbitrary, simply reflecting the complexity of the chemistry of living things versus the simplicity of the chemistry of non-living things

(e)                    Humans have modified this distinction somewhat by creating a gray area in which living things (humans) direct non-living things (laboratory apparatus) to produce somewhat complex, carbon-based molecules

(f)                     Thus, we now understand that there is nothing inherently magical about the ability of life to produce complex chemicals

(g)                    Instead, we recognize that the chemistry (and physics) of life works under the same constraints as the chemistry and physics of nonliving things (that is, we recognize that there exists a mechanistic basis of life)

 

QUICK INTRODUCTION TO CARBON CHEMISTRY

 

(3) Carbon (see also carbon)

(a)                    "The foundation of organic chemistry is not some intangible life force, but the unique chemical versatility of the element carbon."

(b)                    "The carbon atom completes its valence by sharing electrons with other atoms in four covalent bonds. Each carbon thus acts as an intersection point from which a molecule can branch off in up to four directions. This tetravalence is one facet of carbon's versatility that makes large, complex molecules possible."

(c)                    Upon completing its outer shell, carbon's four paired electrons attempt to maximally separate

(d)                   See Figure, Molecular shapes due to hybrid orbitals (Methane)

(e)                    In three dimensions, this places carbon's single covalent bonds at angles "toward the corners of an imaginary tetrahedron."

(f)                     See Figure, The shapes of three simple organic molecules

(g)                    Note that writing structural formulas as though molecules are flat -- See Figure, Variations in carbon skeletons -- fails to take into account this tetrahedral shape, so consequently often fails to capture the complexity of organic molecules

(h)                    Example structures (no need to know the immediately following names or structures unless required to elsewhere):

(i)                     Methane (CH4)

(ii)                   Ethane (3HC-CH3; note that this is hardly a standard-written molecular formula)

(iii)                 Ethene (2HC=CH2; ditto)

(iv)                 Carbon dioxide (O=C=O)

(v)                   Urea (O=C(NH2)2)

(i)                      [organic chemistry (Google Search)] [organic chemistry primer (MicroDude)] [orientation of bonds about carbon (MicroDude)] [index]

(4) Hydrocarbon (see also hydrocarbon)

(a)                    A hydrocarbon is a molecule that consists of only hydrogen and carbon atoms

(b)                    See Figure, Variations in carbon skeletons

(c)                    See Figure, The role of hydrocarbons in the characteristics of fats

(d)                   [hydrocarbon (Google Search)] [hydrocarbon (MicroDude)] [index]

 

ISOMERIC VARIATION IN THE CARBON SKELETON

 

(5) Isomers (see also isomer)

(a)                    Isomers are compounds that share molecular formulas but differ in some way in terms of their structure

(b)                    See Figure, Three types of isomers

(c)                    [isomer (Google Search)] [isomer (MicroDude)] [index]

(6) Structural isomer (see also structural isomer)

(a)                    Structural isomers are the most general case of isomers

(b)                    Structural isomers share molecular formulas but differ in structural formulas

(c)                    see Figure, Three types of isomers (a) Structural Isomers

(d)                   [structural isomer (Google Search)] [structural isomer (MicroDude)] [index]

(7) Geometric isomer (see also geometric isomer)

(a)                    Geometric isomers share both their molecular and their structural formulas

(b)                    Geometric isomers occur as a consequence of the non-rotatability of double bonds (this may need to be seen to be appreciated; see figure or link)

(c)                    see Figure, Three types of isomers (b) Geometric Isomers

(d)                   [geometric isomer (Google Search)] [geometric isomer (MicroDude)] [index]

(8) Enantiomers (see also enantiomer)

(a)                    Enantiomers share both molecular and structural formulas

(b)                    Unlike geometric isomers, however, they are not generated by double bonds

(c)                    They are, however, like geometric isomers a consequence of the non-interchangeability of paired electrons around carbon atoms

(d)                   In other words, a carbon atom which is single bonded to four different atoms or groups can have those groups arranged in up to two different ways (as an aside, these carbons are then described as being chiral, asymmetric, or to exhibit chirality)

(e)                    Furthermore, each of those ways or being orientated constitutes a different molecule (essential a left-handed one and a corresponding right-handed one)

(f)                     Each enantiomer is also a mirror image of the other (note that the definition of enantiomers and stereoisomers differs slightly, but we won't worry about this difference here: enantiomers are true mirror images while stereoisomers are mirror images only in terms of the arrangement of the bonds immediately around, for example, a chiral carbon atom)

(g)                    See Figure, Three types of isomers (c) Enantiomers

(h)                   (photograph ball and stick model for presentation during lecture)

(i)                      Molecules of living things are far more likely to display not just chirality but only one of two (or more) possible enantiomers compared with the molecules of non-living things

(j)                      [enantiomer (Google Search)] [enantiomers (MicroDude)] [index]

 

HYDROPHILIC FUNCTIONAL GROUPS

 

(9) Functional groups (see also functional group)

(a)                    Carbon atoms can bond to elements other than carbon and hydrogen

(b)                    These other elements or groups of elements are together described as groups

(c)                    They may additionally be described as functional groups because these other-than-carbon-and-hydrogen groups tend to be more chemically reactive than hydrocarbons

(d)                   Functional groups "behave consistently from one organic molecule to another, and the number and arrangement of the groups help give each molecule its unique properties."

(e)                    [functional groups, functional group, functional group chemistry (Google Search)] [functional group, organic chemistry primer (MicroDude)] [index]

(10) Hydrophilic functional groups (see also hydrophilic functional groups)

(a)                    Hydroxyl group (-OH)

(b)                    Carbonyl group (=O; aldehydes and ketones)

(c)                    Carboxyl group (O=C-OH; -COOH)

(d)                   Amino group (-NH2)

(e)                    Sulfhydryl group (-SH)

(f)                     Phosphate group (-O-PO3, i.e., -PO4)

(g)                    See Table, Functional groups of organic compounds

(h)                    [hydrophilic functional group (Google Search)] [functional group (MicroDude)] [index]

(11) Hydroxyl group (see also hydroxyl group)

(a)                    The hydroxyl functional group (-OH) is a good hydrogen bonder

(b)                    For low molecular weight organic molecules, the hydroxyl group confers water solubility

(c)                    When an otherwise simple hydrocarbon contains a hydroxyl functional group we give the name of the molecule the suffix -ol (i.e., methane becomes methanol, ethane becomes ethanol, isopropane becomes isopropanol, etc.)

(d)                   Alcohol is the general class that is made up of otherwise simple hydrocarbons that contain a hydroxyl functional group

(e)                    Other molecules whose properties are strongly influenced by the presence of numerous hydroxyl groups are the sugars and, more generally, the carbohydrates

(f)                     [hydroxyl group (Google Search)] [alcohols, hydroxyl group (MicroDude)] [index]

(12) Sulfhydryl group (see also sulfhydryl group)

(a)                    The sulfhydryl functional group is very similar to hydroxyl group except that an S replaces the O

(b)                    (Sulfhydryl groups play a role in stabilizing protein tertiary structure as disulfide bridges)

(c)                    [sulfhydryl group (Google Search)] [sulfhydryl group, thiols (MicroDude)] [index]

(13) Carbonyl group (aldehydes, ketones) (see also carbonyl group, aldehyde, and ketone)

(a)                    Carbonyl functional groups (=O) are good hydrogen bonders

(b)                    Similar to hydroxyl groups, at lower molecular weights the carbonyl group confers water solubility on molecules

(c)                    Molecules containing carbonyl groups may be differentiated into two types, aldehydes and ketones:

(i)                     With aldehydes the =O is found on an end carbon (formaldehyde, which contains only one carbon, is the simplest aldehyde)

(ii)                   With ketones the =O on a middle carbon (acetone, which contains three carbons, is consequently the simplest ketone)

(d)                   The location of the carbonyl group (i.e., what carbon it is attached to) affects chemistry of the containing molecule significantly

(e)                    See Table, Functional groups of organic compounds

(f)                     You will see carbonyl groups in carbohydrates, along with hydroxyl groups, and on some of the sugar-like intermediates of carbohydrate metabolism

(g)                    [carbonyl group, aldehyde, ketone (Google Search)] [aldehydes, carbonyl group, ketones (MicroDude)] [index]

(14) Carboxyl group (see also carboxyl group)

(a)                    The carboxyl functional group (-COOH) is a good hydrogen bonder

(b)                    Similar to hydroxyl groups and carbonyl groups, the carboxyl group confers water solubility on lower molecular weight hydrocarbons

(c)                    The salts of carboxyl groups, with their full (as opposed to partial) negative charge are particularly soluble in water

(d)                   When an otherwise simple hydrocarbon contains a carboxyl functional group we give the name of the molecule the suffix -ic

(i)                     (thus, acetic acid is an example of a two carbon organic acid consisting a single carbon to which a second carbon as a carboxyl group is attached)

(ii)                   (formic acid is the single-carbon example of a carboxyl group-associated molecule--in this case the carboxyl group is attached only to a hydrogen atom and the carboxyl group itself supplies the only carbon atom in this molecule)

(e)                    When the hydrogen of a carboxyl group is replaced with a cation the associated molecule is converted to a salt and subsequently is given the suffix -ate (e.g., -COOH --> -COO- Na+; note that though I used sodium as the metal ion in this example, the cation involved in converting the acid to its salt is not limited to sodium)

(i)                     (acetic acid becomes acetate)

(ii)                   (formic acid becomes formate)

(f)                     Note that in water solution the carboxyl group tends to exist dissociated from both its hydrogen and whatever cation it is otherwise associated with, i.e., it possesses a negative charge (thus making it very soluble in water)

(g)                    The H+ typically dissociate at physiological pHs; thus, under typical physiological conditions carboxyl groups often exist as dissociated salts (try not to get confused on this point, but if you recall your acid-base chemistry, a dissociated weak acid is a weak base, i.e., a hydrogen ion acceptor--thus hydrogens tend to come off of and then go back on to carboxyl groups under physiological conditions)

(h)                    You will see carboxyl groups in amino acids (along with various other functional groups including, particularly, amino groups)

(i)                      [carboxyl group, carboxylic acid (Google Search)] [carboxyl group, carboxylic acids, carboxylic acid salts (MicroDude)] [index]

(15) Amino group (see also amino group)

(a)                    The amino functional group (-NH2) is also a good hydrogen bonder

(b)                    Contrary to the not-disassociated carboxyl group, the amino group functions as weak base (i.e., able to accept H+): -NH2 + H+ --> NH3+

(c)                    Simple carbon compounds possessing amino groups are called amines

(d)                   Amino acids are so-named because they possess an amino group as one of their core structures (among the other core structures is a carboxyl group from which the term acid in amino acid is derived)

(e)                    [amino group (Google Search)] [amino group (MicroDude)] [index]

(16) Phosphate group (inorganic phosphate, Pi) (see also phosphate group)

(a)                    Replace one H of phosphoric acid with carbon and you have a phosphate group (attached to that carbon)

 

phosphoric acid (a.k.a., inorganic phosphate or Pi):

 

OH

|

HO P = O

|

OH

 

phosphate group:

 

OH

|

C - O P = O

|

OH

 

 

(b)                    Phosphates and phosphate groups readily lose hydrogen ions (i.e., they are somewhat acidic)

(c)                    At physiological pHs phosphate groups are highly negatively charged due to their ionization (loss of hydrogen ions)

(d)                   On the other hand, phosphoric acid is typically referred to as inorganic phosphate (abbreviated, Pi) when not bonded to carbon

(e)                    Phosphate groups play important roles especially in the structure of nucleic acids, many of the molecules that make up membranes (phospholipids), and in energy storage associated particularly with the molecule called ATP

(f)                     [phosphate group, inorganic phosphate (Google Search)] [phosphodiester bond group (MicroDude)] [index]

 

OXIDATION OF CARBON

 

(17) Oxidized carbon (see also organic)

(a)                    Carbon atoms display different degrees of oxidation depending on what they are bonded to.

(b)                    In order of increasingly oxidized carbon atoms we have:

(i)                     -C-H (carbon bonded to hydrogen)

(ii)                   -C-OH (carbon bonded to a hydroxyl group, an alcohol, for example, 3H-C-OH, for example)

(iii)                 -C=O (carbon double-bonded to oxygen, 2H-C=O, for example)

(iv)                 -COOH (carbon as part of a carboxyl group, HO-C=O)

(v)                   CO2 (carbon double-bonded, O=C=O, to two oxygen atoms)

(c)                    In terms of molecules that contain only a single carbon atom plus various permutations of hydrogen and oxygen, in order of increasing oxidation of carbon:

(i)                     CH4 (methane)

(ii)                   CH3OH (methanol)

(iii)                 CH2O (formaldehyde)

(iv)                 H-COOH (formic acid)

(v)                   CO2 (carbon dioxide)

(d)                   Note that in the above compounds you see a monotonic decline in the number of hydrogen atoms attached to the carbon in the above molecules such that the hydrogen to carbon ratio (or just plain number of hydrogen atoms) is reduced by one for each increase in oxidation:

(i)                     CH4 (methane), 4 hydrogens (0 oxygens)

(ii)                   CH3OH (methanol), 3 hydrogens (1 oxygen)

(iii)                 CH2O (formaldehyde), 2 hydrogens (1 oxygen)

(iv)                 H-COOH (formic acid), 1 hydrogen (2 oxygens)

(v)                   CO2 (carbon dioxide), 0 hydrogens (2 oxygens)

(e)                    So what?

(i)                     As carbon becomes more oxidized the total energy associated with the bonds about that carbon decreases

(ii)                   Roughly, a carbon-containing molecule becomes more soluble in water the more oxygens associated with the molecule

(iii)                 As organisms extract energy from carbon-containing molecules, they tend to remove hydrogen atoms and add oxygen atoms

(iv)                 Ultimately oxidizing a molecule that contains abundant obtainable energy down to the most oxidized carbon, carbon dioxide

(v)                   Carbon dioxide, which contains no obtainable energy, is released as a waste product (e.g., you exhale)

(f)                     (To help bring some of these points home I will go through the structure of glucose, a partially oxidized carbon-containing molecule)

(g)                    (I will then drive home the point that extraction of energy often involves the oxidation by once-again walking through glycolysis)

(h)                    [oxidation of carbon (Google Search)] [cellular respiration: harvesting chemical energy (MicroDude)] [index]

 

VOCABULARY

 

(18) Vocabulary [index]

(a)                    Aldehydes

(b)                    Amino group

(c)                    Carbon

(d)                   Carbonyl group

(e)                    Carboxyl group

(f)                     Enantiomers

(g)                    Functional groups

(h)                    Geometric isomer

(i)                      Hydrocarbon

(j)                      Hydrophilic functional groups

(k)                    Hydroxyl group

(l)                      Inorganic phosphate

(m)                  Isomers

(n)                    Ketones

(o)                    Mechanistic basis of life

(p)                    Oxidized carbon

(q)                    Phosphate group

(r)                     Pi

(s)                     Structural isomer

(t)                     Sulfhydryl group

(1) Practice questions [index]

(a)                    Arrange the following molecules into order such that the least oxidized (most reduced) is listed first and the most oxidized last: (i) CH4, (ii) CO2, (iii) CH2O (i.e., 2HC=O), (iv) CH3OH (i.e., 3HC-OH), (v) CH2O2 (i.e., HCOOH)

(b)                    Define "tetrahedron" in terms of the arrangement of single covalent bonds around a single carbon atom.

(c)                    Given the molecular formula C2H2R2, where R is some hydrocarbon and the two carbons explicitly described are bonded by a double-covalent bond such that each carbon is double bonded to the other carbon (C=C) and single bonded to just one H and just one R group (i.e., HRC=CRH), draw both geometric isomers.

(d)                   Order the following from most-reduced (most associated energy) carbon-based group to least-reduced (least associated energy) carbon-based group: carbonyl group, carboxyl group, hydroxyl group, and methyl group (a hydrocarbon group, i.e., -CH3).

(e)                    Name (or draw) the functional group that, to form, requires an additional element other than Oxygen, Carbon, Hydrogen, Nitrogen, and/or Sulfur.

(f)                     What do you have, or potentially have when a carbon atom is bonded to four different functional groups?

(i)                     organic compound

(ii)                   mirror images

(iii)                 enantiomers

(iv)                 chirality

(v)                   all of the above

(vi)                 none of the above

(g)                    In which molecule are single covalent bonds arrayed in a tetrahedron around a central carbon atom?

(i)                     COH4

(ii)                   COH2

(iii)                 CO2H2

(iv)                 CO2

(v)                   None of the above

(h)                    Under what circumstances (i.e., molecular structure) would you expect a carbon-containing compound to display two enantiomeric forms?

(i)                      Draw the structural formula of a molecule consisting of a carbon atom that has three functional groups: A carbonyl group, a hydroxyl group, and a sulfhydryl group (none of which are ionized).

(j)                      Draw the structural formula of formate, a negatively charged organic ion possessing only a single carbon atom.

(k)                    Draw an uncharged amino group.

(l)                      Any organic compound that consists of only (and both) the atoms carbon and hydrogen is called a(n) __________ to distinguish it from other organic compounds that possess atoms of additional elements.

(m)                  Matching: (a) enantiomer, (b) functional group, (c) geometric isomer, and (d) structural isomer.

(i)                     Three or more carbons (if consists of only C and H)

(ii)                   Double bond

(iii)                 Chiral (asymmetric) carbon

(iv)                 Not H

(n)                    Which of the following functional groups contains the most oxygen atoms?

(i)                     Amino group

(ii)                   Carbonyl group

(iii)                 Carboxyl group

(iv)                 Hydroxyl group

(v)                   Sulfhydryl group

(o)                    Draw a two-carbon organic compound in which a sulfhydryl group replaces one H. Include all Hs in your structural formula.

(p)                    Which functional group functions as a weak base? (that is, an acceptor of hydrogen ions)

(i)                     Amino group

(ii)                   Carbonyl group

(iii)                 Carboxyl group

(iv)                 Hydroxyl group

(v)                   Sulfhydryl group

(q)                    Draw (correctly), or state what we call the functional group that possesses four oxygen atoms and one phosphorous atom.

(r)                     Arrange these, as they are found in single-carbon compounds, correctly in terms of increasing Carbon oxidation (i.e., from most reduced to most oxidized carbon):

(i)                     Carbon dioxide

(ii)                   Carbonyl group (as in formaldehyde)

(iii)                 Carboxyl group (as in formic acid)

(iv)                 Hydrogen (as in methane)

(v)                   Hydroxyl group (as in methanol)

(s)                     The distinction between organic compounds and inorganic compounds was originally made on the basis of their origin, i.e., the former came from living things while that latter need not. Today we know that the distinction between made by living things and not necessarily made by living things is somewhat arbitrary, simply reflecting the __________ of the chemistry of living things versus the __________ of the chemistry of non-living things.

(t)                     What is an enantiomer?

(u)                    Functional groups contain __________ that are more chemically reactive than those found in hydrocarbons.

(i)                     Elements

(ii)                   Isotopes

(iii)                 Molecules

(iv)                 Photons

(v)                   Prions

(v)                    What is the name of the functional group that tends to be a good hydrogen bonder while relatively simple molecules containing these groups are identified by their possession of the suffix "ol"?

(w)                  Draw the structure of a three-carbon hydrocarbon. Draw the same organic molecule but now containing a single carbonyl functional group. (don't confuse carbonyl with carboxyl)

(x)                    Draw the structure of an aldehyde. Draw the structure of a ketone. Indicate which is which.

(y)                    Draw the structure of phosphoric acid (not ionized).

(z)                    Draw the structures of two different one-carbon containing molecules both of which are less oxidized than carbon dioxide, O=C=O, but more oxidized than methane, CH4. Please indicate which of the molecules you have drawn is more oxidized.

(aa)                 Draw ribose, in ring form, indicating carbon numbering (shown as primes).

(bb)                The valence of carbon is __________.

(cc)                 Which of the following types of isomers differ due to a lack of rotation around double bonds?

(i)                     Enantiomers

(ii)                   Geometric isomers

(iii)                 Mirror-image isomers

(iv)                 Stereoisomers

(v)                   Structural isomers

(dd)               Functional groups are so-described because they are more chemically reactive than __________.

(ee)                 Which of the following functional group(s) do no contain oxygen? (circle all correct answers)

(i)                     Amino group

(ii)                   Carbonyl group

(iii)                 Carboxyl group

(iv)                 Hydroxyl group

(v)                   Phosphate group

(vi)                 Sulfhydryl group

(ff)                  What is an alcohol?

(gg)                Which of the following functional groups typically ionize to form salts?

(i)                     Amino group

(ii)                   Carbonyl group

(iii)                 Carboxyl group

(iv)                 Hydroxyl group

(v)                   Phosphate group

(vi)                 Sulfhydryl group

(hh)                How many oxygen molecules are found in inorganic phosphate (commonly abbreviated Pi--note that inorganic phosphate is not the same thing as a phosphate functional group)?

(ii)                    Order the following in terms of increasing carbon oxidation:

(i)                     CH2O (formaldehyde)

(ii)                   CH3OH (methanol)

(iii)                 CH4 (methane)

(iv)                 CO2 (carbon dioxide)

(v)                   H-COOH (formic acid)

(2) Practice question answers [index]

(a)                    CH4, CH3OH (3HC-OH), CH2O (2HC=O), CH2O2 (HCOOH), CO2

(b)                    when carbon's four electrons, paired or unpaired, attempt to maximally separate they acquire an arrangement which constitutes the four corners of an imaginary tetrahedron, a shape consisting of four faces, each an equilateral triangle.

(c)                    approximately:

 

R R

\ /

C=C

/ \

H H

 

R H

\ /

C=C

/ \

H R

 

(d)                   methyl, hydroxyl, carbonyl, carboxy

(e)                    phosphate

(f)                     (v) all of the above

(g)                    a, COH4, which is an alcohol such that three H and one OH is bound to the central Carbon; that's four single bonds, and they are arrayed as though at the corners of an imaginary tetrahedron

(h)                    Two enantiomers are possible given chirality (a chiral or asymmetric carbon) associated with a central carbon; that is, the carbon is found to four different groups, e.g., H, OH, CH3, and NH2

(i)                      Approximately:

 

OH

|

O = C

|

SH

 

(j)                      Approximately:

 

O-

|

O = C

|

H

 

(k)                    NH2

(l)                      Hydrocarbon

(m)                  (i) (d) structural isomer, (ii) (c) geometric isomer, (iii) (a) enantiomer, (iv) (b) functional group

(n)                    (iii) carboxyl group

(o)                    3HC-CH2-SH

 

H H

| |

H - C - C -SH

| |

H H

 

(p)                    (i) amino group

(q)                    phosphate group

(r)                     (iv) Hydrogen, (v) hydroxyl, (ii) carbonyl, (iii) carboxyl, (i) carbon dioxide

(s)                     complexity, simplicity

(t)                     An enantiomer is one of a pair of structural isomers that share the same formula and structure but are mirror images of each other

(u)                    (i) Elements

(v)                    hydroxyl

(w)                  a carbonyl group looks like this: =O; don't forget to adhere to the octet rule!

(x)                    An aldehyde has the carbonyl group on an end carbon; a ketone has the carbonyl group on a non-end carbon

(y)                    The formula is H3PO4 and the unionized structure basically has three hydroxyl groups and one carbonyl group surrounding a central phosphorous atom

(z)                    The formulas of the possibilities, arranged from less oxidized to more are 3HCOH, 2HCO, and HCOOH where to right of the carbons represent a hydroxyl group, a carbonyl group, and a carboxyl group

(aa)                 [ribose with numbering]

(bb)                4

(cc)                 (ii) Geometric isomers

(dd)               Hydrocarbons (no, not dys-functional groups)

(ee)                 (i) Amino group, (vi) Sulfhydryl group

(ff)                  An alcohol is a hydrocarbon for which one or more hydrogens have been replaced with a hydroxyl group

(gg)                (iii) Carboxyl group is the obvious answer, but I'll also accept (i) Amino group

(hh)                4

(ii)                    (iii) CH4 (methane), (ii) CH3OH (methanol), (i) CH2O (formaldehyde), (v) H-COOH (formic acid), (iv) CO2 (carbon dioxide)

 

Chapter 4, Bio 113 questions:

 

(#) Arrange the following in terms of increasing oxidation of the single carbon atom. To avoid ambiguity, please also indicate which is most oxidized and which is least oxidized.

(i)                       CH2O (formaldehyde)

(ii)                     CH3OH (methanol)

(iii)                    CH4 (methane)

(iv)                   CO2 (carbon dioxide)

(v)                     H-COOH (formic acid)

 

A: (iii) CH4 (methane), (ii) CH3OH (methanol), (i) CH2O (formaldehyde), (v) H-COOH (formic acid), (iv) CO2 (carbon dioxide)

 

(#) In phosphoric acid, there are how many oxygen atoms?

(i)                       zero

(ii)                     one

(iii)                    two

(iv)                   three

(v)                     four

 

A: (v) four

 

(#) Draw the structure of a functional group that readily dissociates (that is, comes apart) at neutral pH.

 

A: this would be a carboxyl group which has formula -COOH but which looks like (i.e., has the structure of) a carbon to which both a hydroxyl and a carbonyl group are attached.

 

(#) Draw a three-carbon aldehyde.

 

A: key is an indication of the double-bond O attached to an end carbon

 

(#) Enantiomers share both formulas and structures. What kind of arrangement of groups around a carbon atom is necessary for the existence of enantiomers.

 

A: The carbon atom must have four different groups bonded to it, i.e., it must be chiral carbon.

 

(#) Geometric isomers share the same molecular and structural formulas. What sort of structure in a carbon-containing compound is absolutely essential for the occurrence of geometric isomers?

 

A: A carbon-to-carbon double bond, though note that while essential, a double bond is not quite sufficient since the groups attached to these carbons must also not be identical.