diff --git a/Code/GraphMol/ChemReactions/Reaction.cpp b/Code/GraphMol/ChemReactions/Reaction.cpp
index c7f22d724..d9d275c94 100644
--- a/Code/GraphMol/ChemReactions/Reaction.cpp
+++ b/Code/GraphMol/ChemReactions/Reaction.cpp
@@ -317,7 +317,7 @@ bool ChemicalReaction::validate(unsigned int &numWarnings,
 bool isMoleculeReactantOfReaction(const ChemicalReaction &rxn, const ROMol &mol,
                                   unsigned int &which) {
   if (!rxn.isInitialized()) {
-    throw ChemicalReactionException("initMatchers() must be called first");
+    throw ChemicalReactionException("initReactantMatchers() must be called first");
   }
   which = 0;
   for (MOL_SPTR_VECT::const_iterator iter = rxn.beginReactantTemplates();
@@ -338,7 +338,7 @@ bool isMoleculeReactantOfReaction(const ChemicalReaction &rxn,
 bool isMoleculeProductOfReaction(const ChemicalReaction &rxn, const ROMol &mol,
                                  unsigned int &which) {
   if (!rxn.isInitialized()) {
-    throw ChemicalReactionException("initMatchers() must be called first");
+    throw ChemicalReactionException("initReactantMatchers() must be called first");
   }
   which = 0;
   for (MOL_SPTR_VECT::const_iterator iter = rxn.beginProductTemplates();
@@ -359,7 +359,7 @@ bool isMoleculeProductOfReaction(const ChemicalReaction &rxn,
 bool isMoleculeAgentOfReaction(const ChemicalReaction &rxn, const ROMol &mol,
                                unsigned int &which) {
   if (!rxn.isInitialized()) {
-    throw ChemicalReactionException("initMatchers() must be called first");
+    throw ChemicalReactionException("initReactantMatchers() must be called first");
   }
   which = 0;
   for (MOL_SPTR_VECT::const_iterator iter = rxn.beginAgentTemplates();
@@ -398,7 +398,7 @@ void addRecursiveQueriesToReaction(
     std::vector<std::vector<std::pair<unsigned int, std::string> > >
         *reactantLabels) {
   if (!rxn.isInitialized()) {
-    throw ChemicalReactionException("initMatchers() must be called first");
+    throw ChemicalReactionException("initReactantMatchers() must be called first");
   }
 
   if (reactantLabels != NULL) {
@@ -576,7 +576,7 @@ bool getMappedAtoms(T &rIt, std::map<int, const Atom *> &mappedAtoms) {
 VECT_INT_VECT getReactingAtoms(const ChemicalReaction &rxn,
                                bool mappedAtomsOnly) {
   if (!rxn.isInitialized()) {
-    throw ChemicalReactionException("initMatchers() must be called first");
+    throw ChemicalReactionException("initReactantMatchers() must be called first");
   }
   VECT_INT_VECT res;
   res.resize(rxn.getNumReactantTemplates());
diff --git a/Code/GraphMol/ChemReactions/SanitizeRxn.cpp b/Code/GraphMol/ChemReactions/SanitizeRxn.cpp
index 86c35176f..c5a82d2a7 100644
--- a/Code/GraphMol/ChemReactions/SanitizeRxn.cpp
+++ b/Code/GraphMol/ChemReactions/SanitizeRxn.cpp
@@ -255,7 +255,6 @@ void fixRGroups(ChemicalReaction &rxn) {
 
 // if we have query atoms without rlabels, make proper rlabels if possible
 //  ensure that every rlabel in the reactant has one in the product
-
 void fixAtomMaps(ChemicalReaction &rxn) {
   int max_atom_map = getMaxProp<int>(
       rxn,
@@ -324,15 +323,67 @@ void fixReactantTemplateAromaticity(ChemicalReaction &rxn) {
 }
 
 void fixHs(ChemicalReaction &rxn) {
+  {
+    //  if mapped Hydrogens in reactants area mapped to heavy atoms
+    //   keep mappings, in all other cases remove them.
+    //   this allows us to merge query hydrogens atoms 
+
+    std::map<int, bool> mappedToNonHeavyProductAtom;
+
+    for(MOL_SPTR_VECT::iterator it = rxn.beginProductTemplates();
+        it != rxn.endProductTemplates();
+        ++it) {
+      int atomMap = 0;
+      for (ROMol::AtomIterator atIt = (*it)->beginAtoms();
+           atIt != (*it)->endAtoms();
+           ++atIt) {
+        Atom *atom = (*atIt);
+        if (atom->getAtomicNum() != 1) { // hydrogen
+          if (atom->getPropIfPresent(common_properties::molAtomMapNumber, atomMap)) {
+            if(atomMap) {
+              mappedToNonHeavyProductAtom[atomMap] = true;
+            }
+          }
+        }
+      }
+    }
+
+    for(MOL_SPTR_VECT::iterator it = rxn.beginReactantTemplates();
+        it != rxn.endReactantTemplates();
+        ++it) {
+      int atomMap = 0;
+      for (ROMol::AtomIterator atIt = (*it)->beginAtoms();
+           atIt != (*it)->endAtoms();
+           ++atIt) {
+        Atom *atom = (*atIt);
+        if (atom->getAtomicNum() == 1) { // hydrogen
+          if (atom->getPropIfPresent(common_properties::molAtomMapNumber, atomMap)) {
+            if(atomMap) {
+              if(mappedToNonHeavyProductAtom.find(atomMap) ==
+                 mappedToNonHeavyProductAtom.end()) {
+                atom->clearProp(common_properties::molAtomMapNumber);
+              } else {
+                BOOST_LOG(rdWarningLog) <<
+                    "Reaction has explicit hydrogens, reactants will need explicit hydrogens (addHs)"
+                                        << std::endl;
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
   const bool mergeUnmappedOnly = true;
   for(MOL_SPTR_VECT::iterator it = rxn.beginReactantTemplates();
       it != rxn.endReactantTemplates();
       ++it) {
     RWMol * rw = dynamic_cast<RWMol*>(it->get());
-    if (rw)
+    if (rw) {
       MolOps::mergeQueryHs(*rw, mergeUnmappedOnly);
+    }
     else
-      PRECONDITION(rw, "Oops, not really a RWMol?");    
+      PRECONDITION(rw, "Oops, not really an RWMol?");    
   }
 }
 
diff --git a/Code/GraphMol/ChemReactions/SanitizeRxn.h b/Code/GraphMol/ChemReactions/SanitizeRxn.h
index 9893e4505..a79259cd7 100644
--- a/Code/GraphMol/ChemReactions/SanitizeRxn.h
+++ b/Code/GraphMol/ChemReactions/SanitizeRxn.h
@@ -82,7 +82,22 @@ inline const MolOps::AdjustQueryParameters DefaultRxnAdjustParams() {
 }
 
 // Default adjustment parameters for ChemDraw style matching of reagents
+//  -- deprecated - renamed MatchOnlyAtRgroupsAdjustParams
+//  -- this doesn't match sciquest style searching
 inline const MolOps::AdjustQueryParameters ChemDrawRxnAdjustParams() {
+  BOOST_LOG(rdWarningLog) <<
+      " deprecated -- please use MatchOnlyAtRgroupsAdjustParams instead" << std::endl;
+  MolOps::AdjustQueryParameters params;
+  params.adjustDegree = true;
+  params.adjustDegreeFlags = MolOps::ADJUST_IGNOREDUMMIES;
+  params.adjustRingCount = false;
+  params.adjustRingCountFlags = MolOps::ADJUST_IGNORENONE;
+  params.makeDummiesQueries = false;
+  params.aromatizeIfPossible = true;
+  return params;
+}
+
+inline const MolOps::AdjustQueryParameters MatchOnlyAtRgroupsAdjustParams() {
   MolOps::AdjustQueryParameters params;
   params.adjustDegree = true;
   params.adjustDegreeFlags = MolOps::ADJUST_IGNOREDUMMIES;
diff --git a/Code/GraphMol/ChemReactions/Wrap/rdChemReactions.cpp b/Code/GraphMol/ChemReactions/Wrap/rdChemReactions.cpp
index 9d9f08f54..32fd99d2a 100644
--- a/Code/GraphMol/ChemReactions/Wrap/rdChemReactions.cpp
+++ b/Code/GraphMol/ChemReactions/Wrap/rdChemReactions.cpp
@@ -816,7 +816,10 @@ Sample Usage:\n\
                 "Returns the default adjustment parameters for reactant templates");
 
     python::def("GetChemDrawRxnAdjustParams", RDKit::RxnOps::ChemDrawRxnAdjustParams,
-                "Returns the chemdraw style adjustment parameters for reactant templates");
+                "(deprecated, see MatchOnlyAtRgroupsAdjustParams)\n\tReturns the chemdraw style adjustment parameters for reactant templates");
+
+    python::def("MatchOnlyAtRgroupsAdjustParams", RDKit::RxnOps::MatchOnlyAtRgroupsAdjustParams,
+                "Only match at the specified rgroup locations in the reactant templates");
 
     std::string docstring = "feed me";
     python::def(
diff --git a/Code/GraphMol/ChemReactions/testReaction.cpp b/Code/GraphMol/ChemReactions/testReaction.cpp
index a616ea162..1956a9646 100644
--- a/Code/GraphMol/ChemReactions/testReaction.cpp
+++ b/Code/GraphMol/ChemReactions/testReaction.cpp
@@ -43,6 +43,7 @@
 #include <GraphMol/ChemReactions/ReactionPickler.h>
 #include <GraphMol/ChemReactions/ReactionRunner.h>
 #include <GraphMol/ChemReactions/ReactionUtils.h>
+#include <GraphMol/ChemReactions/SanitizeRxn.h>
 #include <GraphMol/FileParsers/FileParsers.h>
 #include <GraphMol/Atom.h>
 #include <fstream>
@@ -5985,6 +5986,410 @@ void test64Github1266() {
   BOOST_LOG(rdInfoLog) << "Done" << std::endl;
 }
 
+void test65SanitizeUnmappedHs() {
+  BOOST_LOG(rdInfoLog) << "-------------------------------------" << std::endl;
+  BOOST_LOG(rdInfoLog) << "Tests sanitize reaction (unmapped Hs) "
+                       << std::endl;
+
+  const std::string unmappedHs = \
+      "$RXN\n" \
+      "\n"                      \
+      "  Marvin       031701170941\n"           \
+      "\n"                                      \
+      "  1  1\n"                                \
+      "$MOL\n"                                  \
+      "\n"                                      \
+      "  Mrv1583 03171709412D          \n"      \
+      "\n"                                      \
+      " 16 16  0  0  0  0            999 V2000\n"                       \
+      "   -2.5620    0.5265    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "   -2.4235   -0.2868    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "   -3.0587   -0.8133    0.0000 C   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "   -3.8322   -0.5265    0.0000 C   0  0  0  0  0  0  0  0  0  4  0  0\n" \
+      "   -3.3355    0.8133    0.0000 C   0  0  0  0  0  0  0  0  0  6  0  0\n" \
+      "   -1.7581    0.7120    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -3.0942    1.6022    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -4.5124    0.9090    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -4.3663   -1.1553    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -3.3000   -1.6022    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -3.8242    1.4780    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -2.2307    1.2821    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -3.9706    0.2868    0.0000 C   0  0  0  0  0  0  0  0  0  5  0  0\n" \
+      "   -2.5700   -1.4780    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -1.6500   -0.5736    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "   -4.6278   -0.3082    0.0000 H   0  0  0  0  0  0  0  0  0  0  0  0\n" \
+      "  1  2  1  0  0  0  0\n"                                         \
+      "  5  1  1  0  0  0  0\n"                                         \
+      "  1  6  1  0  0  0  0\n"                                         \
+      "  1 12  1  0  0  0  0\n"                                         \
+      "  2  3  1  0  0  0  0\n"                                         \
+      "  2 15  1  0  0  0  0\n"                                         \
+      "  3  4  1  0  0  0  0\n"                                         \
+      "  3 10  1  0  0  0  0\n"                                         \
+      "  3 14  1  0  0  0  0\n"                                         \
+      "  4  9  1  0  0  0  0\n"                                         \
+      "  4 13  1  0  0  0  0\n"                                         \
+      "  4 16  1  0  0  0  0\n"                                         \
+      "  5  7  1  0  0  0  0\n"                                         \
+      "  5 11  1  0  0  0  0\n"                                         \
+      " 13  5  1  0  0  0  0\n"                                         \
+      " 13  8  1  0  0  0  0\n"                                         \
+      "M  END\n"                                                        \
+      "$MOL\n"                                                          \
+      "\n"                                                              \
+      "  Mrv1583 03171709412D          \n"                              \
+      "\n"                                                              \
+      "  6  6  0  0  0  0            999 V2000\n"                       \
+      "    3.8966    0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "    4.6111    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "    4.6111   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "    3.8966   -0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  4  0  0\n" \
+      "    3.1821   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  5  0  0\n" \
+      "    3.1821    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  6  0  0\n" \
+      "  1  2  1  0  0  0  0\n"                                         \
+      "  6  1  1  0  0  0  0\n"                                         \
+      "  2  3  1  0  0  0  0\n"                                         \
+      "  3  4  1  0  0  0  0\n"                                         \
+      "  4  5  1  0  0  0  0\n"                                         \
+      "  5  6  1  0  0  0  0\n"                                         \
+      "M  END";
+  
+  ChemicalReaction *rxn = RxnBlockToChemicalReaction(unmappedHs);
+  TEST_ASSERT(rxn);
+  rxn->initReactantMatchers();
+  MOL_SPTR_VECT reacts1, hreacts1, reacts2, hreacts2;
+  std::vector<MOL_SPTR_VECT> prods;
+  
+  reacts1.push_back(ROMOL_SPTR(SmilesToMol("C1CCCCC1")));
+  hreacts1.push_back(ROMOL_SPTR(MolOps::addHs(*reacts1[0].get())));
+  
+  reacts2.push_back(ROMOL_SPTR(SmilesToMol("C1CCCCC1Cl")));
+  hreacts2.push_back(ROMOL_SPTR(MolOps::addHs(*reacts2[0].get())));
+
+  // test with and without AddHs
+  prods = rxn->runReactants(reacts1);
+  TEST_ASSERT(prods.size() == 0);
+  prods = rxn->runReactants(hreacts1);
+  TEST_ASSERT(prods.size() == 768);
+  
+  prods = rxn->runReactants(reacts2);
+  TEST_ASSERT(prods.size() == 0);
+
+  prods = rxn->runReactants(hreacts2);
+  TEST_ASSERT(prods.size() == 128);
+
+  // Test after sanitization (way fewer matches than with AddHs..)
+  RxnOps::sanitizeRxn(*rxn);
+  prods = rxn->runReactants(reacts1);
+  TEST_ASSERT(prods.size() == 12);
+
+  prods = rxn->runReactants(reacts2);
+  TEST_ASSERT(prods.size() == 4);
+  
+
+  delete rxn;
+  
+  BOOST_LOG(rdInfoLog) << "Done" << std::endl;
+
+}
+
+
+
+void test66SanitizeMappedHs() {
+  BOOST_LOG(rdInfoLog) << "-------------------------------------" << std::endl;
+  BOOST_LOG(rdInfoLog) << "Tests sanitize reaction (mapped hs in react but not prod) "
+                       << std::endl;
+
+  // H's are mapped in reactant but do not exist in product,
+  //  they can be merged
+  const std::string unmappedHs = \
+      "$RXN\n" \
+      "\n"                      \
+      "  Marvin       031701170941\n"           \
+      "\n"                                      \
+      "  1  1\n"                                \
+      "$MOL\n"                                  \
+      "\n"                                      \
+      "  Mrv1583 03171709412D          \n"      \
+      "\n"                                      \
+      " 16 16  0  0  0  0            999 V2000\n"                       \
+      "   -2.5620    0.5265    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "   -2.4235   -0.2868    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "   -3.0587   -0.8133    0.0000 C   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "   -3.8322   -0.5265    0.0000 C   0  0  0  0  0  0  0  0  0  4  0  0\n" \
+      "   -3.3355    0.8133    0.0000 C   0  0  0  0  0  0  0  0  0  6  0  0\n" \
+      "   -1.7581    0.7120    0.0000 H   0  0  0  0  0  0  0  0  0  7  0  0\n" \
+      "   -3.0942    1.6022    0.0000 H   0  0  0  0  0  0  0  0  0  8  0  0\n" \
+      "   -4.5124    0.9090    0.0000 H   0  0  0  0  0  0  0  0  0  9  0  0\n" \
+      "   -4.3663   -1.1553    0.0000 H   0  0  0  0  0  0  0  0  0 10  0  0\n" \
+      "   -3.3000   -1.6022    0.0000 H   0  0  0  0  0  0  0  0  0 11  0  0\n" \
+      "   -3.8242    1.4780    0.0000 H   0  0  0  0  0  0  0  0  0 12  0  0\n" \
+      "   -2.2307    1.2821    0.0000 H   0  0  0  0  0  0  0  0  0 13  0  0\n" \
+      "   -3.9706    0.2868    0.0000 C   0  0  0  0  0  0  0  0  0  5  0  0\n" \
+      "   -2.5700   -1.4780    0.0000 H   0  0  0  0  0  0  0  0  0 14  0  0\n" \
+      "   -1.6500   -0.5736    0.0000 H   0  0  0  0  0  0  0  0  0 15  0  0\n" \
+      "   -4.6278   -0.3082    0.0000 H   0  0  0  0  0  0  0  0  0 16  0  0\n" \
+      "  1  2  1  0  0  0  0\n"                                         \
+      "  5  1  1  0  0  0  0\n"                                         \
+      "  1  6  1  0  0  0  0\n"                                         \
+      "  1 12  1  0  0  0  0\n"                                         \
+      "  2  3  1  0  0  0  0\n"                                         \
+      "  2 15  1  0  0  0  0\n"                                         \
+      "  3  4  1  0  0  0  0\n"                                         \
+      "  3 10  1  0  0  0  0\n"                                         \
+      "  3 14  1  0  0  0  0\n"                                         \
+      "  4  9  1  0  0  0  0\n"                                         \
+      "  4 13  1  0  0  0  0\n"                                         \
+      "  4 16  1  0  0  0  0\n"                                         \
+      "  5  7  1  0  0  0  0\n"                                         \
+      "  5 11  1  0  0  0  0\n"                                         \
+      " 13  5  1  0  0  0  0\n"                                         \
+      " 13  8  1  0  0  0  0\n"                                         \
+      "M  END\n"                                                        \
+      "$MOL\n"                                                          \
+      "\n"                                                              \
+      "  Mrv1583 03171709412D          \n"                              \
+      "\n"                                                              \
+      "  6  6  0  0  0  0            999 V2000\n"                       \
+      "    3.8966    0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "    4.6111    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "    4.6111   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "    3.8966   -0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  4  0  0\n" \
+      "    3.1821   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  5  0  0\n" \
+      "    3.1821    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  6  0  0\n" \
+      "  1  2  1  0  0  0  0\n"                                         \
+      "  6  1  1  0  0  0  0\n"                                         \
+      "  2  3  1  0  0  0  0\n"                                         \
+      "  3  4  1  0  0  0  0\n"                                         \
+      "  4  5  1  0  0  0  0\n"                                         \
+      "  5  6  1  0  0  0  0\n"                                         \
+      "M  END";
+  
+  ChemicalReaction *rxn = RxnBlockToChemicalReaction(unmappedHs);
+  TEST_ASSERT(rxn);
+  rxn->initReactantMatchers();
+  MOL_SPTR_VECT reacts1, hreacts1, reacts2, hreacts2;
+  std::vector<MOL_SPTR_VECT> prods;
+  
+  reacts1.push_back(ROMOL_SPTR(SmilesToMol("C1CCCCC1")));
+  hreacts1.push_back(ROMOL_SPTR(MolOps::addHs(*reacts1[0].get())));
+  
+  reacts2.push_back(ROMOL_SPTR(SmilesToMol("C1CCCCC1Cl")));
+  hreacts2.push_back(ROMOL_SPTR(MolOps::addHs(*reacts2[0].get())));
+
+  // test with and without AddHs
+  prods = rxn->runReactants(reacts1);
+  TEST_ASSERT(prods.size() == 0);
+  prods = rxn->runReactants(hreacts1);
+  TEST_ASSERT(prods.size() == 768);
+  
+  prods = rxn->runReactants(reacts2);
+  TEST_ASSERT(prods.size() == 0);
+
+  prods = rxn->runReactants(hreacts2);
+  TEST_ASSERT(prods.size() == 128);
+
+  // Test after sanitization (way fewer matches than with AddHs..)
+  RxnOps::sanitizeRxn(*rxn);
+  prods = rxn->runReactants(reacts1);
+  TEST_ASSERT(prods.size() == 12);
+
+  prods = rxn->runReactants(reacts2);
+  TEST_ASSERT(prods.size() == 4);
+
+  delete rxn;
+  
+  BOOST_LOG(rdInfoLog) << "Done" << std::endl;
+
+}
+
+void test67SanitizeMappedHsInReactantAndProd() {
+  BOOST_LOG(rdInfoLog) << "-------------------------------------" << std::endl;
+  BOOST_LOG(rdInfoLog) << "Tests sanitize reaction (mapped hs in react and prod) "
+                       << std::endl;
+
+  // H's are mapped in reactant and in prod
+  //  they can be merged
+  const std::string unmappedHs = \
+      "$RXN\n" \
+      "\n"                      \
+      "  Marvin       031701171002\n"           \
+      "\n"                                      \
+      "  1  1\n"                                \
+      "$MOL\n"                                  \
+      "\n"                                      \
+      "  Mrv1583 03171710022D          \n"      \
+      "\n"                                      \
+      " 16 16  0  0  0  0            999 V2000\n"                       \
+      "   -3.1881    0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "   -2.4736    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "   -2.4736   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "   -3.1881   -0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  4  0  0\n" \
+      "   -3.9025    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  6  0  0\n" \
+      "   -2.8178    1.5622    0.0000 H   0  0  0  0  0  0  0  0  0  7  0  0\n" \
+      "   -4.3559    1.1018    0.0000 H   0  0  0  0  0  0  0  0  0  8  0  0\n" \
+      "   -4.6170   -0.8250    0.0000 H   0  0  0  0  0  0  0  0  0  9  0  0\n" \
+      "   -3.5583   -1.5622    0.0000 H   0  0  0  0  0  0  0  0  0 10  0  0\n" \
+      "   -2.0203   -1.1018    0.0000 H   0  0  0  0  0  0  0  0  0 11  0  0\n" \
+      "   -4.7262    0.4605    0.0000 H   0  0  0  0  0  0  0  0  0 12  0  0\n" \
+      "   -3.5583    1.5622    0.0000 H   0  0  0  0  0  0  0  0  0 13  0  0\n" \
+      "   -3.9025   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  5  0  0\n" \
+      "   -1.6500   -0.4605    0.0000 H   0  0  0  0  0  0  0  0  0 14  0  0\n" \
+      "   -1.7591    0.8250    0.0000 H   0  0  0  0  0  0  0  0  0 15  0  0\n" \
+      "   -2.8178   -1.5622    0.0000 H   0  0  0  0  0  0  0  0  0 16  0  0\n" \
+      "  1  2  1  0  0  0  0\n"                                         \
+      "  5  1  1  0  0  0  0\n"                                         \
+      "  1  6  1  0  0  0  0\n"                                         \
+      "  1 12  1  0  0  0  0\n"                                         \
+      "  2  3  1  0  0  0  0\n"                                         \
+      "  2 15  1  0  0  0  0\n"                                         \
+      "  3  4  1  0  0  0  0\n"                                         \
+      "  3 10  1  0  0  0  0\n"                                         \
+      "  3 14  1  0  0  0  0\n"                                         \
+      "  4  9  1  0  0  0  0\n"                                         \
+      "  4 13  1  0  0  0  0\n"                                         \
+      "  4 16  1  0  0  0  0\n"                                         \
+      "  5  7  1  0  0  0  0\n"                                         \
+      "  5 11  1  0  0  0  0\n"                                         \
+      " 13  5  1  0  0  0  0\n"                                         \
+      " 13  8  1  0  0  0  0\n"                                         \
+      "M  END\n"                                                        \
+      "$MOL\n"                                                          \
+      "\n"                                                              \
+      "  Mrv1583 03171710022D          \n"                              \
+      "\n"                                                              \
+      " 17 17  0  0  0  0            999 V2000\n"                       \
+      "    4.1309    0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "    4.8454    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "    4.8454   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "    4.1309   -0.8250    0.0000 C   0  0  0  0  0  0  0  0  0  4  0  0\n" \
+      "    3.4165   -0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  5  0  0\n" \
+      "    3.4165    0.4125    0.0000 C   0  0  0  0  0  0  0  0  0  6  0  0\n" \
+      "    4.5012    1.5622    0.0000 H   0  0  0  0  0  0  0  0  0 13  0  0\n" \
+      "    3.7607    1.5622    0.0000 H   0  0  0  0  0  0  0  0  0  7  0  0\n" \
+      "    5.6690    0.4605    0.0000 H   0  0  0  0  0  0  0  0  0 15  0  0\n" \
+      "    5.2987    1.1018    0.0000 H   0  0  0  0  0  0  0  0  0 17  0  0\n" \
+      "    5.2987   -1.1018    0.0000 H   0  0  0  0  0  0  0  0  0 14  0  0\n" \
+      "    3.7607   -1.5622    0.0000 H   0  0  0  0  0  0  0  0  0 16  0  0\n" \
+      "    2.9631   -1.1018    0.0000 H   0  0  0  0  0  0  0  0  0  9  0  0\n" \
+      "    2.5929   -0.4605    0.0000 H   0  0  0  0  0  0  0  0  0 18  0  0\n" \
+      "    2.7020    0.8250    0.0000 H   0  0  0  0  0  0  0  0  0  8  0  0\n" \
+      "    4.5012   -1.5622    0.0000 H   0  0  0  0  0  0  0  0  0 10  0  0\n" \
+      "    5.6690   -0.4605    0.0000 H   0  0  0  0  0  0  0  0  0 11  0  0\n" \
+      "  1  2  1  0  0  0  0\n"                                         \
+      "  6  1  1  0  0  0  0\n"                                         \
+      "  1  7  1  0  0  0  0\n"                                         \
+      "  1  8  1  0  0  0  0\n"                                         \
+      "  2  9  1  0  0  0  0\n"                                         \
+      "  2 10  1  0  0  0  0\n"                                         \
+      "  2  3  1  0  0  0  0\n"                                         \
+      "  3  4  1  0  0  0  0\n"                                         \
+      "  3 11  1  0  0  0  0\n"                                         \
+      "  3 17  1  0  0  0  0\n"                                         \
+      "  4  5  1  0  0  0  0\n"                                         \
+      "  4 12  1  0  0  0  0\n"                                         \
+      "  4 16  1  0  0  0  0\n"                                         \
+      "  5  6  1  0  0  0  0\n"                                         \
+      "  5 14  1  0  0  0  0\n"                                         \
+      "  5 13  1  0  0  0  0\n"                                         \
+      "  6 15  1  0  0  0  0\n"                                         \
+      "M  END\n";
+  
+  ChemicalReaction *rxn = RxnBlockToChemicalReaction(unmappedHs);
+  TEST_ASSERT(rxn);
+  rxn->initReactantMatchers();
+  MOL_SPTR_VECT reacts1, hreacts1, reacts2, hreacts2;
+  std::vector<MOL_SPTR_VECT> prods;
+  
+  reacts1.push_back(ROMOL_SPTR(SmilesToMol("C1CCCCC1")));
+  hreacts1.push_back(ROMOL_SPTR(MolOps::addHs(*reacts1[0].get())));
+  
+  reacts2.push_back(ROMOL_SPTR(SmilesToMol("C1CCCCC1Cl")));
+  hreacts2.push_back(ROMOL_SPTR(MolOps::addHs(*reacts2[0].get())));
+
+  // test with and without AddHs
+  prods = rxn->runReactants(reacts1);
+  TEST_ASSERT(prods.size() == 0);
+  prods = rxn->runReactants(hreacts1);
+  TEST_ASSERT(prods.size() == 768);
+  
+  prods = rxn->runReactants(reacts2);
+  TEST_ASSERT(prods.size() == 0);
+
+  prods = rxn->runReactants(hreacts2);
+  TEST_ASSERT(prods.size() == 128);
+
+  // Test after sanitization (way fewer matches than with AddHs..)
+  RxnOps::sanitizeRxn(*rxn);
+  prods = rxn->runReactants(reacts1);
+  TEST_ASSERT(prods.size() == 12);
+
+  prods = rxn->runReactants(reacts2);
+  TEST_ASSERT(prods.size() == 4);
+  
+
+  delete rxn;
+  
+  BOOST_LOG(rdInfoLog) << "Done" << std::endl;
+
+}
+void test68MappedHToHeavy() {
+  const std::string rxnblock = \
+      "$RXN\n" \
+      "\n" \
+      "  Marvin       031701171005\n" \
+      "\n" \
+      "  1  1\n" \
+      "$MOL\n" \
+      "\n" \
+      "  Mrv1583 03171710052D          \n" \
+      "\n" \
+      "  3  2  0  0  0  0            999 V2000\n" \
+      "   -1.2721   -0.0116    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "   -1.9866   -0.4241    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "   -1.2721    0.8134    0.0000 H   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "  2  1  1  0  0  0  0\n" \
+      "  1  3  1  0  0  0  0\n" \
+      "M  END\n" \
+      "$MOL\n" \
+      "\n" \
+      "  Mrv1583 03171710052D          \n" \
+      "\n" \
+      "  3  2  0  0  0  0            999 V2000\n" \
+      "    2.3886   -0.0563    0.0000 C   0  0  0  0  0  0  0  0  0  1  0  0\n" \
+      "    1.6741   -0.4688    0.0000 C   0  0  0  0  0  0  0  0  0  2  0  0\n" \
+      "    2.3886    0.7688    0.0000 C   0  0  0  0  0  0  0  0  0  3  0  0\n" \
+      "  2  1  1  0  0  0  0\n" \
+      "  1  3  1  0  0  0  0\n" \
+      "M  END\n";
+
+  ChemicalReaction *rxn = RxnBlockToChemicalReaction(rxnblock);
+  TEST_ASSERT(rxn);
+  rxn->initReactantMatchers();
+  MOL_SPTR_VECT reacts1, hreacts1, reacts2, hreacts2;
+  std::vector<MOL_SPTR_VECT> prods;
+  
+  reacts1.push_back(ROMOL_SPTR(SmilesToMol("CC")));
+  hreacts1.push_back(ROMOL_SPTR(MolOps::addHs(*reacts1[0].get())));
+  
+  // test with and without AddHs
+  prods = rxn->runReactants(reacts1);
+  TEST_ASSERT(prods.size() == 0);
+
+  prods = rxn->runReactants(hreacts1);
+  TEST_ASSERT(prods.size() == 6);
+
+  std::stringstream sstrm;
+  rdWarningLog->SetTee(sstrm);
+  RxnOps::sanitizeRxn(*rxn);
+  std::string s = sstrm.str();
+  std::cerr << s << std::endl;
+  TEST_ASSERT(s.find("Reaction has explicit hydrogens, reactants will need explicit hydrogens (addHs)") != std::string::npos);
+  rdWarningLog->ClearTee();
+
+  delete rxn;
+}
+
 int main() {
   RDLog::InitLogs();
 
@@ -6062,6 +6467,11 @@ int main() {
 
   test43Github243();
   test64Github1266();
+  test65SanitizeUnmappedHs();
+  test66SanitizeMappedHs();
+  test67SanitizeMappedHsInReactantAndProd();
+  test68MappedHToHeavy();
+  
   BOOST_LOG(rdInfoLog)
       << "*******************************************************\n";
   return (0);
diff --git a/ReleaseNotes.md b/ReleaseNotes.md
index b501c5607..93d6fecfe 100644
--- a/ReleaseNotes.md
+++ b/ReleaseNotes.md
@@ -345,7 +345,11 @@ Vianello, Maciek Wojcikowski
 
 ## Deprecated code (to be removed in a future release):
   - rdkit.VLib python module
-
+  - SanitizeRxn parameters "ChemDrawRxnAdjustParams" has been renamed to
+    "MatchOnlyAtRgroupsAdjustParams".  These settings did not reflect
+    how integrations with SciQuest or the Perkin Elmer ELN behaved and
+    were confusing to users (especially since they were not explicit)
+    
 ## Removed code:
 
 ## Contrib updates: